2. Definition:
• Non-reducing substances
• On hydrolysis (acids or enzymes)
Glycone (one or more sugar)
+ Aglycone.
Importance:
1) As medicinal agents.
2) Potential source of new drugs.
3) Role in the plants; regulatory, protective... etc.
• Examples are: Cardiac stimulant as digitoxin and
analgesic as salicin
5. Acid Hydrolysis
Most of the glycosides containing the normal sugars are quite
resistant to hydrolysis and need strong acids with heating.
2-deoxy sugar (e.g. cardiac glycosides) are cleaved by weak
acids even at room temperature .
C-glycosides require an oxidizing agent for hydrolysis e.g.,
FeCl3 or H2O2.
CN
O--D-glucose--D-glucose
Amygdalin
N-O-SO3K
S--D-glucose
6. Alkaline Hydrolysis
• Alkali has no action the glycosidic linkages.
They can cause breakage either in the
aglycone or in the sugar:
1) The acetyl-ester group (or any ester linkage): mild alkaline hydrolysis.
2) Lactone ring (cardiac glycosides): strong alkali.
O
O
OH
OR
OH
HO
O
O
O
7. CARDIAC GLYCOSIDES HYDROLYSIS:
1-Acid Hydrolysis
2- Alkaline hydrolysis
A- Deacetylation in sugar
B- Lactone opening
O
O
D
14
OH
O
O
D
14
OH
H OH
OH
O
O
OH
OH
H+
Active
3- Enzymatic hydrolysis
Remove the terminal sugar (Glucose)
Digilanidase for digitalis glycoside
Yeast enzyme for straphanthus glycoside
Strophanthobiase for straphanthus glycoside
8. Enzymatic Hydrolysis
Specific in action.
Glycosides with rhamnose moiety: Rhamnase.
o Exceptions for enzyme
1) Emulsin hydrolyses any of the β-glycosides
2) Myrosin all sulfur-cotaining glycosides.
C
N
S glucose
OSO3K + H2O
N C S
+ KHSO4 + Glucose
Myrosin
H+
OH-
9. Sugars present in glycosides
• One molecule of a monosaccharide, e.g., Salicin.
• Two or more molecules of monosaccharide which
may be similar or different.
• The polarity is increased with the number sugar units.
• Their linkage to the aglycone may be:
– A chain as a disaccharide, …etc, at one position.
– At two or three different positions at the
aglycone, e.g. Sennoside.
• Hexose series, Pentose series, Methylpentose, 2-
Desoxy-sugar or uronic acids.
10. Aglycones
Aglycones:
• Non-sugar part: Wide variety of compounds
containing free hydroxyl-group.
• Glycoside formation = Aldehyde group of sugar is
blocked.
• According to nature of aglycone, glycosides can be
classified into:
1) Holosides:
Aglycone is also a sugar, e.g. maltose, lactose ,,,etc.
2) Heterosides:
Aglycone is a non-sugar, e.g. rutin, digitoxin,
sinigrin, barbaloin ... etc.
11. Classification of Glycosides (Heterosides)
1) Chemical nature of the aglycone into:
1. Phenol : Arbutin.
2. Alcohol : Salicin.
3. Lactone : Daphnin.
4. Flavone : Rutin.
5. Anthraquinone : Gluco-aloe-emodin.
6. Aldehyde : Gluco-vanillin.
7. Cyanophore : Amygdalin.
8. Thiocyanate : Sinigrin.
9. Steroid : Digitoxin.
10. Saponin : Digitonin.
11. Other types of aglycones.
2) A specific group in the molecule: Examples:
• Cyano-group (CN) Cyanogenetic glycosides (Amygdalin).
• Sulphur (S) Thioglycoside (Sinigrin).
12. 3) Physiological activity: Examples:
• Cardiac glycoside
• Laxative Glycosides…etc.
• Two main groups according to nature.
Primary glycosides:
The unchanged from, occurring in the fresh plant , e.g., Purpurea
glycoside A
Secondary glycosides:
The result from the hydrolysis of other glycoside by enzymatic
activity with splitting of one or more sugar unit, e.g., Digitoxin.
4) The nature of glycoside:
Primary glycoside,
e.g. Purpurea glycoside A
Secondary glycoside + Sugar
Enzyme
Hydrolysis
13. Nomenclature
1- Trivial names:
in--ending, indicates the source of the glycoside.
• Example: digitoxin from Digitalis and salicin from Salix
2- According to the simple sugar produced on hydrolysis
ending with (oside), generally glycoside.
3- Systematic names :
For Heteroside, usually :
chemical name: (α- or β-) (D or L) (sugar-ose) oside.
Prefix anomeric configurational Suffix
• Systematic name :O-hydroxymethylphenyl β-D-glucopyranoside.
14. • For Holoside: e.g., Maltose.
O O
CH2OH
OH
OH
OH
OH
CH2
OH
H,OH
O
4
1 1
OH
4-O-(-D-Glucopyraosyl)-D-glucopyranose.
(osyl) can be replaced by osido)
15. General Scheme:
1)Formation of phosphorylated sugar:
2)Activation of phosphorylated sugar with nucleotide: UTP =
Uridine triphosphate.
3)Activated sugar: UDPG = Uridine diphosphate glucose.
4)The reaction:
1 2 3 4
Glucose - 1 - P + UTP UDPG + P - P
Biosynthesis of Glycoside
The sugar is transferred to another sugar (in case of
holosides) or to aglycone (in case of heteroside) by means of
the nucleotide, UTP = Uridine triphosphate.
16. UDPG + Aglycone Glucoside + UDP
Enzymatic
Galactose-1- P + UDPG Glucose-1- P + UDP-Galactose
Enzyme
(Transferase)
b) Heteroside: Transfer of activated sugar to aglycone.
2) Exchange reactions of glycosides:
3) Glucuronide formation: Oxidation products of hexoses.
Reactions of UDPG:
1) Formation of glycosides:
a) Holoside: Transfer of activated sugar to another sugar.
UDPG + Fructose Sucrose + UDP
Enzymatic
Glucose - 1 - P + UTP UDPG + P - P
UDPG is oxidized into UDPGlucuronate and then transfer
17. Properties of glycosides:
• Colorless, crystalline, non-volatile solids.
• Bitter taste, exceptions, e.g., populin is sweet.
• Fehling‟s reagent -ve, After hydrolysis +ve.
*when they have a reducing group in their
molecule +ve.
• Soluble in water and hydro-alcohol.
• Insol. in ether; exception: Steroid-glycoside.
• Usually levorotatory.
18. Pharmacological action of glycosides is due to the aglycone.
Roles of the sugar in the molecule are :
I. Stabilization.
II. Solubilization.
III. Modify the pharmacodynamic properties of the aglycone.
IV.Carry the aglycone to the site of its action.
PHARMACOLOGICAL ACTIVITY:
Chemical properties:
The reactions due to aglycone:
Most of the characteristic chemical tests for glycosides are due to the
aglycone moieties.
The reactions due to sugar part:
The potential of the glycosides to reduce Fehling's solution after
hydrolysis is due to the release of the sugar part.
19. Extraction and isolation of glycosides:
Common Solvents are water and alcohol.
Precautions in extraction procedure:
1) Inactivation of enzymes: By one of the following methods:
– Boiling with alcohol or acetone.
– Drying at 1000C for 15 minutes then slow drying at low temperature.
– Extraction at a very low temperature, e.g., by liquid CO2.
– Freeze drying.
2) Insurance of neutral condition: Calcium carbonate in case of plant
rich in acid.
3) Defatting: By petroleum ether in case of plants rich in lipids.
4) Removal of other constituents: Such as tannin and resin ...etc.
• By treating with lead acetate. (not used for drugs containing flavonoids?).
5) Use of chromatography for isolation:
• Silica, cellulose, polyamide, etc column chromatography.
20. Estimation of glycosides:
For sugar:
oQualitative tests (fehling's test, Osazone test,..etc)
oQuantitative assays (copper reduction, iodometry,
enzymatic)
For aglycone:
oQualitative tests.
oQuantitative assays.
• Bioassay: by testing the biological action of
the glycoside.
• Spectroscopic methods such as GC-MS, ..etc
21. Occurrence of glycosides:
• They may be present in any organ of the
plant, i.e., roots ,Fruits, leaves, Seeds ,Flowers.
• Glycosides content varies in different species
in the same genus, and also in the same plant
in different seasons.
• Present in the cell vacuole and sometimes
localized in certain cells.
• They are accompanied by their specific
enzymes that are capable of synthesizing or
hydrolyzing them.
22. Functions of glycosides in plants:
• Reserved energy (sugar -content).
• Regulatory role in plant physiology.
• Detoxifying role.
• Defense role against micro-organisms and
insects.
23. Some aliphatic, aromatic and alicyclic
nuclei presented in glycosides
Benzene Naphthalene Anthracene 2H-Pyrane -Pyrone
Isoprene
side chain
O O O
Benzo--pyrone
(Coumarin)
1
2
3
4
5
6
7
8
9
10
or
Phenanthrene skeleton as
drawn in opium alkaloids
Phenanthrene skeleton
as drawn in glycosides
1
3
4
5
6
8
9
10
1
3
4
5 6
8
9
10
1
3
4
5
6
8 9 10 O O
24.
1
4
2
3
5
8 9
10
1
2
3
4
5
6
7
8
Benzo-
quinone Naphthaquinone Anthraquinone -Pyrone
O
O
O
O O
O
O O
4H-Pyrane
O
Benzo--pyrane
(Chromane)
O
2
3
4
5
7
8 1 1'
2'
3'
4'
5'
6'
Benzo--pyrone
(Chromone)
2-Substituted Chromane
Flavonoids
3-Substituted Chromane
4-Substituted Chromane
Isoflavane
Flavane
Isoflavonoids
Neoflavane Neoflavonoids
9
10
O
O
O
A
B
C
25. HO
3
14
13
H
Basic type of triterpene (C30)
[Tetracyclic or Pentacyclic]
H at C(13) and -CH3 at C(14)]
(trans/trans/trans)
HO
Basic type of steroids (C30)
-CH3 at C(13)]
3
14
13
(trans/trans/trans)
Steroid-Saponin C27
trans-trans-trans
Cardenolides C23 or 24
= (C21 +2 or + 3)
cis-trans-cis
Bile salts C24
trans-trans-cis
Corticosteroids C21
Different reactions
and migrations
Sex hormones C19
HO
H
Sterol (C27)
3
14
13
17
18
19
-CH3 at C(13)]
(trans/trans/trans)
24
20
21
26 27
26. glycosides
Phenolic
• A large group of plant secondary metabolites:
• Aromatic moieties.
• Range from simple structures with one
aromatic ring to highly complex polymeric
substances such as tannins and lignin.
• Widely spread in nature.
• Important constituents of many medicinal
plants.
27. Classification of Glycosides:
I. Simple phenolic glycosides: C6only to C6-C3
II. Phenolics consisting of C6-C4: Naphthquinones.
III. Phenolics consisting of C6-C2-C6:
Anthraquinones.
IV. Phenolics consisting of C6-C3-C3-C6: Lignans
and neo-lignans.
V. Phenolics consisting of C6-C3-C6: Flavonoids
and related glycosides.
VI. Phenolics consisting of C6-C3-C6-C3- C6: Flavo-
lignans or Ligno-flavons.
28. I) Simple phenolic glycosides:
A. Having C6 only: e.g. arbutin.
B. Having C6-C1: The C1-part is present as :
• Alcoholic group: e.g. Salicin, populin.
• Aldehyde group: e.g. green vanilla glycosides and
vanillin.
• A carboxylic acid group: e.g. Gaultherin,…etc
C. Having C6-C2 (Phenyl-ethanoids): e.g. Acteoside,…etc
D. Having C6-C3 (Phenyl propanoids): The C3-part may be:
• Chain: e.g. coniferin and hemi-lignan.
• Cyclic: e.g. coumarins.
29. I- Simple Phenolic Glycosides
A) Simple phenolic glycosides consisting of C6 only
Arbutin:
Uva ursi, Arctostaphylos uva-ursi, Ericaceae.
Hydroquinone-1--D-glucopyranoside.
White needles, sol. in water and in alcohol
OH
O--D-Glucose
OH
OH
+ H2O
H+
+ Glucose
Arbutin Hydroquinone
Blue color with ferric chloride solution.
Test using plant powder:
1) The powder + dilute HCl on a slide.
2) Heat on a small flame.
Flame
Sublimate
Powdered drug
Slides
Micro-Sublimation
Uses:
1) Renal antiseptic
2) A good inhibitor for melanin synthesis and may be used in Hyperpigmentation
disorders (as bleaching agent).
1) Collected sublimate (hydroquinone) needle-shaped crystals giving colorwith FeCl3.
Estimation:
Iodometric.
30. B) Simple phenolic glycosides consisting of C6-C1: The C1-part is present as :
a) An alcoholic group: e.g. Salicin, populin.
1) Salicin:
Willow bark, in particular Salix fragilis and S. purpurea, Family
Salicaceae.
H+ or
Emulsin
+ Glucose
+ H2O
Salicin Saligenin
CH2OH
O -D-Glucose
CH2OH
OH
Properties:
Prismatic crystals, Sparingly sol. in cold water, very sol. in
hot. , very bitter taste.
Levorotatory
Hydrolysis (acid or emulsin) glucose + saligenin
Saligenin, on boiling with acid saliretin.
31. HO
O
HO
OH
OH
O
HO
HO
HO
O
HO
OH
OH
OH
HO
glucose
Saligenin
(salicyl alcohol)
1) Hydrolysis into saligenin + Glucose
2) Saligenin combine together to give a
water insoluble yellow compound called
Saliretin.
H2SO4
bright red color
H2O
Disappear
Froehde’s
Mandalin
Erdman
FeCl3
violet
purple bright red No color
FeCl3
blue color.
Potassium dichromate
+ dil. sulfuric acid
odor of
salicylaldehyde
32. :
Identity tests for salicin
• Salicin develops the following colors:
• Salicin + potassium dichromate acidulated
with sulfuric acid + odor of salicylaldehyde.
• Hydrolysis: Saligenin + ferric chloride
blue color.
• Use of salicin: Anti-pyretic, anti-reuhmatic
and diaphoretic.
Salicin
+ Conc. H2SO4 Bright red color
+ Freohde reagent Violet color
+ Mandalin reagent Purple color
+ Erdmann reagent Red color
33. )
salicin
-
Benzoyl
: (
Populin
)
2
• Bark + leaves of Populus species( Salicaceae).
• Soluble in water, sweet taste.
Test for Identity:
• Populin develops the same colors
with the color reagents
mentioned under salicin.
• Populin + potassium dichromate
acidulated with sulfuric acid
odor of salicylaldehyde.
Hydrolysis:
• Alkali benzoic acid and salicin.
• Acids: saligenin and 6-benzoyl-glucose.
• Acid hydrolysis followed by alkaline hydrolysis Salignin +
benzoic acid + glucose.
HO
O
HO
OH
OH
O
COO
Benzoic acid
Moitty
Alcoholic group
Phenolic
group
Glucose
34. Populin
HO
O
HO
OH
OH
O
COO
benzoylsalicin
Tests for identity:
It behaves like salicin towards
Froehde’s reagent and concentrated sulfuric acid.
HO
O
HO
OH
OH
O
HO
COOH
Acid Or
HO
HO
O
HO
OH
OH
OH
COO
Taka-diastase enzyme
saligenin + benzoic acid + glucose
benzoic acid and salicin.
6-benzoyl-glucose
saligenin
35. B) Simple phenolic glycosides consisting of C6-C1:
The C1-part is present as:
b) An aldehyde group:
Green vanilla glycosides and vanillin
• Vanillin:
• Green vanilla bean is the full-grown unripe fruits of Vanilla
planifolia (Orchidaceae).
• It contains two glycosides, glucovanillin and glucovanillic
alcohol. During curing of vanilla, these glucosides are
hydrolyzed and oxidized into vanillin
Fine, white to yellow, needle-like crystals, Odor and taste of
vanilla.
Slightly soluble in water and glycerin.
Freely soluble in alcohol, chloroform and ether.
Use: Flavoring agent.
Properties of Vanillin
36. Industrial Preparation of Vanillin
• Vanillin from wood (containing coniferin):
• Preparation of Vanillin from eugenol:
• Oxidation with acid dichromate needst protection of the
hydroxyl-group by acetylation.
• Oxidation without protection of the hydroxyl-group: use
nitrobenzene (C6H5.NO2) or ozone (O3) as oxidizing agents.
Conifer Wood
Super heated steam
Coniferin Cr2O3
Chromic acid mixture
Vanillin
CHO
OCH3
OH
Isomerisation
KOH
1)Acetylation, 2) Oxidation
3) Acidification (HCl)
Eugenol Isoeuginol
H2
C
OCH3
OH
C CH2
H
HC
OCH3
OH
C CH3
H
Vanillin
CHO
OCH3
OH
Vanillin
37. c) A carboxylic acid group as ester: e.g.
Gaultherin and monotropin
• Monotropin: “Primary glycoside”
• Chemically: Methyl salicylate glucoxyloside
• Both (leaves of Gaultheria procumbens. Fam. Ericaceae).
O
OH
OH
OH
O
OH
OH
OH
O
CO-O-CH3
Xylose Glucose
Primverose
Methyl-
salicylate
Monotropin"Primary Glycoside"
Methyl salicylate glucoxyloside
Gaultherin"Secondary Glycoside
Methyl salicylate Glucoside
O CH2
Monotropin (Primary) Methylsalicylate (Aglycone) + Primverose (Disaccharride)
Gaultherase
Monotropin (Primary) Gaultherin (Secondary) + Xylose
Enzyme
Gaultherin (Secondary) Gaultherase Methylsalicylate (Aglycone) + Glucose
38. C) Simple phenolic glycosides Consisting of C6-C2 (Phenyl-ethanoids):
e.g. Orobanchoside, acteoside,…etc (It will not be studied).
D) Simple phenolic glycosides consisting of C6 - C3:
(Phenyl propanoids):
The C3-part may be:
a) Chain: e.g. coniferin
b) Cyclic: e.g. coumarins.
39. a) Chain: e.g. coniferin and hemi-lignan.
1) Coniferin:
• p-Hydroxy-m-methoxy-cinnamylalcohol-4--D-glucopyranoside.
• Conifer plants, in cambium, lignified tissues.
• White needle-shaped crystals
• slightly soluble in water, more in hot.
• Bitter taste, Levorotatory.
Identity test:
• Conc. H2SO4 Red color.
• Phloroglucinol and conc. Red color
Importance in plant:Precursors of lignin biosynthesis
Importance in industry: Preparation of vanillin.
Coniferin
CH2OH
OCH3
O -D-Glucose
2) Hemi-lignan: It will be dealt with under lignans.
40. b) Cyclic: Coumarins.
• Leguminosae (Fabacease), Umbelliferae (Apiaceae),
Rubiaceae and Thymeliaceae.
• Free state and as glycosides.
• Derivatives of benzo--pyrone, (coumarin).
• Generally:
1) Hydroxy-group at C-7.
2) Other hydroxyl-groups or methoxy-groups
• Coumarins are lactones of ortho-hydroxy cis-cinnamic
acid:
1) Dilute alkali opens pyrone ring forming a salt of ortho-
hydroxy-cis-cinnamic acid.
2) Acidification regenerates coumarin.
3) All coumarins have fluorescence in UV 366 nm.
41. Biosynthesis:
• cinnamic acid or its derivatives:
Glycosidation, isomerization, and cyclization
to give a coumarin.
• More complex coumarins result from the
addition of structural units from other
biosynthetic pathways, e.g., Isoprene side
chain from mevalonic acid pathway
42. Natural coumarins:
• Umbelliferone: It is the lactone of umbellic acid.
– Asafoetida and galbanum.
– Ammoniacal solution shows a green-blue fluorescence.
• Action: regulator for normal growth of plants.
Umbelliferon (R = H)
Herniarin (R = CH3)
Skimmin (R = Glucose)
O O
RO
7
43. antibiotic novobiocin
• coumarin unit in the middle
• Rest of molecule originates from several biogenetic units from different
pathways:
1) Coumarin and p-hydroxybenzoyl-group from shikimate.
2) Noviose sugar from Calvin cycle.
3) Isopentenyl-group from mevalonic acid.
Isoprntenyl
group from
mevalonate
p-Hhdroxy-
benzoyl group
from
shikimate
Noviose, a sugar
derived from glucose
(Photosynthesis)
+ Amide group
(CONH2)
+ 2 methyl groups
Coumarin
from shikimate
Novobiocin
H
N
O O
OH
O
O
H3CO
OH
H2N
O
44. Uses:
• Protection UV rays.
• Reduction of varicose symptoms.
• Antibacterial activity, e.g.. Umbelliferone.
• Antibiotic Novobiocin has a coumarin-moiety.
• Dicumarol (Bishydroxycoumarin): Anticoagulant.
Dicumarol
Bishydroxycoumarin
O O O
O
OH
OH
Furano- & Pyrano-coumarins will be discussed
under the topic of Bitterprinciples.
II) Phenolics consisting of C6-C4: Naphthquinones.
45. III) Phenolics consisting of C6-C2-C6:
Anthraquinone glycosides
• Presentation in nature:
• In higher plants, they occur in:
– Monocotyledons: The only family, that contains anthracene glycosides,
is Liliaceae as C-glycosides.
– Dicotyledons: They occur in many families such as Rubiaceae,
Leguminosae (Fabaceae), Polygonaceae and Rhamnaceae.
• In lower plants, they occur in certain fungi and lichens. Examples of fungi
are Aspergillus.
• Anthracene glycosides: different oxidation level.
• Laxatives derivatives: 1,8-dihydroxy-compounds, mainly:
a) 1, 8-Dihydroxy-anthraquinone.
b) 1, 8-Dihydroxy-anthrone
46. Classification of anthracene derivatives:
According to the oxidation level into the following classes:
• Anthraquinones (oxidized).[1]
• Anthranols and anthrones [3]are tautomers (reduced).
Anthrone: C-10, methylene carbon, easily oxidized.
Reduced forms exist only in the combined form as
glycosides.
• Oxanthrone and anthrahydroquinone are tautomers.[2]
• Dianthrones [4]
The four mentioned subgroups may occur in the form of:
1) Aglycones: In the drug, they are always as
anthraquinones.
2) O-glycosides.
3) C- glycosides.
48. :
Biosynthesis of anthracene derivatives
CH3-C S-CoA 7 HOOC-
CH2-C S-
CoA
+
Acetyl-CoA Malon
yl-
CoA
Cyclization
Oxidation
Emodin dianthrone
Emodin
Anthrone derivative
Emodin anthrone
Decarboxylation
O OH
OH
HO CH3
COOH
O
O
CH3
S-CoA
O
O
O
O
O
O O O
O OH
OH
HO CH3
CH3
OH
OH O
H
H
HO
Oxidative coupling
O OH
OH
HO CH3
O OH
OH
HO CH3
O
1)Generally, condensation
of:
• 1 mole of acetyl Co-A.
• 7 moles of malonyl-Co-A.
To form polyketide skeleton
as intermediate (Poly-β-
keto-methylene acid).
2) Cyclization leading to the
formation of derivatives
of anthrone.
3) Dianthrones are formed
from monomeric by
oxidative coupling of
phenols.
49. 1) Anthraquinones
• Tricycle skeleton of C6-C2-C6 series.
• Anthraquinone derivatives as purgative have:
1) Phenolic OH-groups in various positions and 1, 8-dihydroxy is a must.
2) The following at position (3), i.e., C-3:
- CH3 e.g., Frangula-emodin.
- CH2OH e.g., Aloe emodin.
- COOH e.g., Rhein.
• Orange or red colored compounds.
• Soluble in hot water and in dilute alcohol.
• Present in plants as aglycones or in the form of glycosides.
• The glycosidation may be at various positions.
50. Reduction
Zn dust / HCl
Anthraquinone Anthrone Anthranol
Tautomerism
Alcohol
OH
H H
O
O
O
• Anthraquinones can be reduced to anthrone with tin (Sn)/ HCl.
• Tests for identity:
1) Bornträger’s test:
Boil with dilute HCl; extract with ether, separate ether.
Add to the ether, aqueous ammonia (NH3) or (NaOH).
The aqueous layer aquires a pink, red or violet color.
The test can be done on a slide by mounting the powdered
vegetable drug in alkali; red color can be noted by the means of
microscope, indicating the location of anthraquinone in the tissue.
• Solution of anthrone in alcohol contains an equilibrium mixture
of anthrone and the tautomeric form, anthranol.
51. 2) Micro-sublimation:
The powdered drug is heated on a slide to 160 -1800C.
A sublimate on the lower surface of the upper slide is formed as
needles or droplets.
The sublimate assumes a red coloration upon adding a drop of alkali
Flame
Sublimate
Powdered drug
Slides
Micro-Sublimation
52. Substitution pattern of 1, 8-dihydroxy-anthraquinone
R2
R1
Name
-H
-CH3
Chrysophanol (Chrysophanic acid)
-H
-CH2OH
Aloe emodin
-H
-COOH
Rhein
-OH
-CH3
Emodin (=Frangula-emodin=Rheum-emodin)
-OCH3
-CH3
Physcion
Glucofrangulin - Glucose - Rhamnose
Frangulin Frangula-emodin
i) Emodin:
a) Frangula emodin:
•It occurs in both free and combined state.
•Frangulin gives on hydrolysis frangula-emodin and rhamnose.
b) Aloe-emodin:
•Orange red needles, sol. in acetone, insol. in water and sol. in dilute alkali.
•In both free and combined state in Cascara bark, Senna leaves and Aloes.
53. ii) Rhein:
• It is the parent substance for sennoside A & B / C & D.
• It can be separated from emodins by extracting in sodium
bicarbonate aqueous solution (due to the presence of a -
COOH group).
Reduction
Zn dust / HCl
Chrysophanic
acid Chrysarobin
O
O
OH
OH
CH3
OH OH
OH
CH3
iii) Chrysophanic acid:
• Yellow needles, sol. in chloroform, sparingly sol. in ethanol,
insol. in water.
• + Alkali Red color.
• It is reduced by Zinc dust and HCl into chrysarobin.
• Chrysophanic acid occurs in cascara, frangula, rhubarb and
senna.
Rhein
O OH
OH
COOH
O
54. 2) Anthranol and anthrone
• The anthrones and/or anthranols:
A) Free B) As glycosides.
• Reduced form of anthraquinone.
• Isomeric: Anthranol ↔ anthrone.
• During storage of crude drugs:
Anthranols Anthraquinones (by oxidation).
1,8-Dihydroxyanthranol 1,8-Dihydroxyanthrone
OH OH
OH O OH
OH
H H
55. Anthranol Anthrone
Fluorescent Non-fluorescent
Soluble in alkali Insoluble in alkali
Schöntetens‟ test (Borax test):
Extract + borax Green fluorescence.
+ water Intensified. (pH of borax aq. solution = 9.5)
p-Nitroso-dimethylaniline:
Different members of this group give different colors.
Anthraquinone Negative.
• Tests for identity:
Glycosidation of anthranol and anthrone:
• At Phenolic hydroxyl-group (O-glycosides).
• At a carbon atom (C- glycosides), e.g., aloin.
56. i) Chrysarobin:
Yellowish-red to wine-red prisms,sol. in EtOH,
CHCl3, insol. in H2O.
It dissolves in alkali to give a deepred color
with green fluorescence.
Preparation form natural source:√√√
By benzene extraction of araroba, a natural powder
obtained from the trunk of the tree Andira araroba, Family Leguminosae
(Fabaceae). Araroba = Goa powder
Use: Keratolytic in cases of psoriasis and some other sorts of skin dermatitis.
Examples of anthranol and anthrone group:
Chrysarobin
OH OH
OH
CH3
Barbaloin
H -D-Glucose
O OH
OH
CH2OH
ii) Barbaloin:
• C-glycoside of aloe-emodin anthrone.
• Several optical isomers, barbaloin and isobarbaloin.
iii) Aloin: It is a mixture of C-glycosides obtained from
different Aloe species.
1) Soluble in water, ethanol and alkali.
2) Aloin solution in alkalis shows red color with green fluorescence.
3) Preparation: Extract with boiling acidulated water, cool, filter to
remove resins, concentrate, allow cooling. Aloin crystallizes out as
yellow crystals.XXXXXXXX
57. • Oxanthrone:
• Intermediate between Anthraquinone and anthranol. Rare occurrence.
Dianthrone Anthrone A Anthrone B
Homodianthrone
Sennidin A and B Rhein Rhein
Emodin dianthrone Emodin Emodin
Heterodianthrone
Sennidin C and D Rhein Aloe-emodin
Rheidin A Rhein Emodin
Rheidin C Rhein Physcion
• Dianthrone
They are derived from two anthrone molecules which may be:
• Identical ....... (Homo-dianthrone).
• Different....... (Hetero-dianthrone).
Examples for homo- and heterodianthrones (Aglycones)
58. Action site: In colon after 6 -12 hours, after transportation through stomach,
duodenum and small intestine.
Drug Anthraquinone Dianthrone + Aloin
Transport
1) Stomach
2) Duodenum
3) Ileum
Glycoside Glycosides
Splitting
+
Reduction
Splitting
+
Hdrolytic splitting
4) Colon
End Product Free anthrone or anthranol
(Act by irritation of colon mucosa)
Side effects: In high dosage:
•Urinary tract irritation, vomiting and diarrhea.
•Uterine pain.
General use: As laxative.
59. Principal structure
1,8-Dihydroxyanthrone
e.g. Barbaloin
1'
8'
1
8
3'
3
10
10'
9
10
1
4
5
8
3
Principal structure
1,8-Dihydroxyanthrquinone
Anthraquinone glycoside
e.g.
Glucofrangulin A (-Rhamnose)
Glucofrangulin B (-Rhamnose)
Anthrone O-Glycoside Anthrone-C-glycoside
Gluc.
Gluc.
Dianthrone glycoside
(Homo- and Hetero-
dianthrone
e.g.
Sennoside A and B
e.g. Frangularoside
Glucofrangulin anthrone
1
2 3
4
O OH
OH
O OH
O
O CH3
O
Rhamnose
Glucose
O
O OH
OH
H H
O OH
O
O CH3
Rhamnose
Glucose
O OH
O
COOH
COOH
OH
O O
H
H
O
OH
HO
OH
HO
O OH
OH
CH2OH
H
The Four Principal Groups of Anthracene Glycosides
60. Vegetable drugs containing laxative anthracene
derivatives
Classified according to the principle active substance.
a) Drugs containing anthraquinone glycosides and partly
anthrone glycosides:
1) Rhubarb root. 2) Frangula bark. (Stored).
b) Drugs containing dianthrone glycosides:
1) Frangula bark (fresh) 2) Rhubarb root
3) Senna leaves 4) Senna fruits.
c) Drugs containing aloin and aloinosides: Aloe
61. I) Aloe:
There are four types of aloes; namely:
1. Cape aloe: From Aloe ferox, Fam. Liliaceae.
It contains barbaloin and isobarbaloin.
2. Curaçao aloe: From Aloe vera, Fam. Liliaceae.
It contains barbaloin and isobarbaloin.
3. Socotrine aloe & Zanzibar aloe: From Aloe Perryi, Fam. Liliaceae.
They contain barbaloin but don't contain isobarbaloin.
Tests for identity:
1. Borträger‟s test: As in the general test (mentioned before).
2. Borax Test: Aqueous solution gives with borax, a green fluorescence
which is intensified by the addition of water. It is due the aloe-emodin
anthranol liberated from barbaloin by hydrolysis.
62. 3. Bromine water: Yellow precipitate with aq. Soln. of aloe.
4. Nitric acid: According to origin of aloe different colors:
- Cape aloe: …… Yellowish-brown color
Vivid green.
- Curaçao aloe: … Deep brownish-red color
- Socotrine & Zanzibar aloe: …Yellowish brown.
5. Cupraloin test for isobarbaloin:
Warming aqueous solution of aloe
+ a drop of CuSO4 solution
+ 0.5 ml of NaCl solution + 1 ml of ethanol:
- Cape aloe......... Deep wine red color.
- Cura oa aloe....Pale wine red color.
The color is due to isobarbaloin; indicating that cape
aloe has high percentage in comparison to Curacao aloe as
regard isobarbaloin %.
- Socotrine and Zanzibar aloe have no isobarbaloin: -ve.
63. II) Rhubarb
Origin: Rheum palmatum and R. officinale, Fam.
Polygonaceae.
2.5% of anthracene derivatives. (2/3 are anthraquinone
derivatives and 1/3 are anthranol derivatives).
Tannins and flavonoids.
Anthraquinone: Mainly chrysophanol, aloe-emodin,
rhein, emodin and physcion as aglycones and glycosides.
Anthrone: Monomers and mainly dimers anthrone such as
sennidin, rheidin, palmidin in the form of glycosides.
Adulteration: R. rhaponticum. (Stilbene-derivatives).UV
64. III) Frangula bark
Origin: Frangula alnus, Fam. Rhamnaceae.
Principal active constituents: 2% of 1, 6, 8-trihydroxy-3-
methyl-anthraquinone (frangula emodin), (3/10 anthranol
derivatives : frangula emodin anthrone).
√√√
Fresh drug Stored drug
Glucofrangulin
Dianthrone
Frangula-emodin
Loss of Activity
Reduced form Oxidized form
Loss of Activity
Splitting, Partial hydrolysis and Oxidation
65. IV) Cascara
Origin: The bark of Rhamnus purshiana Fam. Rhamnceae.
8% C-glycoside & O-glycoside:-
I) C- glycosides: 80 - 90%
mainly barbaloin and chrysaloin
I) O- glycoside: 20 - 10% mainly glycosides of emodin, emodin-anthrone.
II) Cascarosides: (A, B, C & D).
A = (+) barbaloin with additional glucose as O-glycosides.
B = (-) barbaloin with additional glucose as O-glycosides.
C = (+) Chrysaloin with additional glucose as O-glycosides.
D = (-) Chrysaloin with additional glucose as O-glycosides
Barbaloin Chrysaloin
H -D-Glucose
O OH
OH
H -D-Glucose
O OH
OH
CH3
CH2OH
H -D-Glucose
O OH
O
H -D-Glucose
O OH
O
CH3
CH2OH
Glucose
Glucose
Cascaroside A & B Cascaroside C & D
66. V) Senna Leaves and fruits
• Alexandrian senna, Cassia acutifolia (leaves, fruits).
• Tinnevelly senna, Cassia angustifolia (fruits, leaves).
• The principal anthracene glycosides are the diathrone glycosides; namely:
Sennoside A and B: Alexandrian senna leaves 2.5%
Alexandrian senna fruits 3.0%
• Aloe emodin glycosides: 12 – 20 % of total glycosides of senna leaves
• Rhein, rhein-8- glucosides and chrysophanol glucoside:
Present in senna fruits.
• Sennoside C and D:
Present in senna leaves.
67. R1 R2 10/10'
Sennoside A COOH COOH trans
Sennoside B COOH COOH meso
Sennoside C CH2OH COOH trans
Sennoside D CH2OH COOH meso
O OH
O
R1
R2
OH
O O
H
H
C6H11O5
C6H11O5
68. VI) Phenolics consisting of C6-C3-C3-C6:
Lignans and Neo-lignans.
• Lignans are dimer compounds
formed by the union of molecules
of phenylpropene derivatives
by stereospecific, reductive
coupling between the middle
carbon of the side chain of the
monomer (β-β' linkage). Coniferyl alcohol
CH2OH
OCH3
OH
CH2OH
OH
CH2OH
OCH3
OH
p -Coumaryl alcohol
H3CO
Sinapyl alcohol
'
• More than 300 lignans have been isolated and recognized in a number of
groups according to structural features.
Biosynthesis: XXX
1) Generation of coniferyl alcohol by reduction of ferulic acid.
2) Oxidative dimerization of 2 units of coniferyl alcohol through β-β' linkage.
3) Variation in the degree of substitution and oxidation to yield different
lignans.
CH2OH
OCH3
OH
CH2OH
O CH2OH
OCH3
O
H3CO
HO
OCH3
OH
H3CO
O
O
H
H
HO
OCH3
OCH3
H3CO
O
O
H3CO
OH
Coniferyl alcohol
Oxidation Dimerization
2 X
'
Podophyllotoxin
69. • Neo-lignans:
• They are also derived
from the same units as
lignans but the C6-C3
moities are linked head
to tail and not through the β-β' carbons.
• Example: Magnolol; a bioactive neolignan of the bark of
Magnolia officinalis; Family Magnoliaceae.
CH2
H2C
HO
OH
Magnolol
Neolignan
'
'
'
• Lignin is an important polymeric substance, (C6-C3)n ,
laid down in the matrix of cellulose microfibrils to
strengthen certain cell walls (vessels, trachieds, fibres and
sclereids).
70. •Lignin of the different classes of Plant Kingdom: XXXXX
1) Lignin of Gymnosperm is formed from coniferyl alcohol.
2) Lignin of Dicots is formed from coniferyl and sinapyl alcohol.
3) Lignin of Gymnosperm is formed from p-coumaryl, coniferyl and
sinapyl alcohols.
•Types of lignans: XXXXXXX
1) Furano-type lignan.
2) Dibenzylbutane-type lignan.
3) Tetrahydrofuran-type lignan.
4) Aryltetralin-type lignan.
5) Dibenzocyclooctadiene-type lignan.
6) Flavonolignan.
•Lignans of Podophyllum: They are of
the aryltetralin-type and are formed from
2 molecules of coniferyl alcohol or the
corresponding acid derivatives with
subsequent modifications. The most
important is podophyllotoxin, α-peltatin
and β-peltatin.
O
O
O
OH
OCH3
OCH3
H3CO
O
'
Podophyllotoxin
O
O
O
OR
OCH3
H3CO
O
'
OH
-Peltatin R = CH3
-Peltatin R = H
71. VI) Phenolics consisting of C6-C3-C6: Flavonoids and related glycosides.
IV) Flavonoids glycosides
2
3
4
5
7
8 1 1'
2'
3'
4'
5'
6'
Benzo--pyrone
(Chromone)
2-Substituted Chromane
Flavonoids
3-Substituted Chromane
4-Substituted Chromane
Isoflavane
Flavane
Isoflavonoids
Neoflavane Neoflavonoids
9
10
O
O
O
A
B
C
• The name flavone ……………. Phenyl-benzopyrone skeleton.
• Latin word “Flavus” = English word “Yellow”.
• Most widely distributed class of natural oxygen heterocyclic:
- C6-C3-C6 carbon skeleton
- Chroman ring bears a second aromatic ring in position 2, 3 or 4.
• In some cases, the six-membered heterocyclic ring is replaced by a
five- membered ring (aurones), or exists in an open chain isomeric
form (chalcones).
• Present in plants both in the free state as aglycone or combined
with defferent sugars as glycosides.
• Methylated, acylated, prenylated, or sulfated derivatives.
72. •They are of abundant occurrence in many families of plant kingdom
such as Leguminosae (Fabaceae), Umbelliferae (Apiaceae), Compositae
(Asteraceae), Rutaceae ...etc
•Although flavone itself is colorless, almost all flavone derivatives are
yellow due to the presence of conjugated double bonds where the
presence of 2 is a must.
•The intensity of the yellow color is increased with the increased number
of OH-groups and with increase of pH (Alkali).
• Solubility of flavonoids:
Glycosides are generally water-soluble and alcohol-soluble.
The aglycones are sparingly soluble in water but soluble in ether.
They dissolve in alkalis yielding yellow solution, which is
decolorized by addition of acids.
73. Pharmacological effects of flavonoids:
Effect on capillaries: Normalization of capillary permeability and
decrease of capillary fragility leading to reduction of capillary bleeding,
e.g. rutin, hesperidin.
• Effect on heart and vessels: Heart tonics and reduce blood
pressure through the capillary dilatation.
• Diuretic, e.g. Buchu.
• Spasmolytic, choleretic and cholagogue.
• Isoflavone derivatives have a distinct estrogenic effect.
Function in plant:
1) As flower pigment to attract birds and insects.
2) Plant growth control.
3) Protection against diseases.
4) Inhibitor and activator of enzyme.
74. Biosynthesis:
Condensation of three moles of malonyl-Co A and one
mole of cinnamoyl-Co-A to form C15-skeleton (C6-C3-C6),
followed by:
A) Cyclization reaction between C (1) and C (6) produces the
flavonoid series though the following reactions:
1) Claisen type cyclization creates ring A and produces
the chalcone structure.
2) Subsequent reaction closes the ring C.
3) Different oxidation degree in the hetero-cycle ring
“pyrane ring” or “Ring C” produces the different
classes of flavonoids.
B) Cyclization reaction between C (2) and C (7), followed by
decarboxylation, produces the stilbene sereis.
75. 3 HOOC-CH2
-C ~ SCoA CoAS ~ C-CH=CH
O
O
O
O O
O
+
CoAS ~ C-CH2 - C - CH2 - C - CH2 - C - CH = CH
1 2 3 4 5 6 7
8
9
1
3
5 7
Malonyl-CoA Cinnamoyl-CoA
1
2
CO2
Chalcone Derivative
Stillbene Derivative
Claisen
Cyclization
- SCoA
- SCoA
- SCoA
Aurone
Isoflavone Flavanone
2 1
Isomerisation
- 2 H
Different Classes of Flavonoids
R1
R2
R3
R1
R2
R3 R1
R2
R3
C
O
SCoA
O
O O
R1
R2
R3
OH
HO
OH O
C
C
H
H
HO
HO
R2
R1
R3
R1
R2
R3
HO
OH
R1
R2
R3
O
HO
OH O
O
C
H
O
R1
R2
R3
O
HO
OH O
1 6
2 7
Biosynthesis
of
flavonoids:
76. The variation in the structure of flavone-derivatives is
originated from the following:
A.Different oxidation pattern of ring C, i.e., different
classes of flavonoids.
B.Others
1) Number and position of OH-groups at ring A and B.
2) Combination of the phenolic hydroxyl-group or groups
with different sugars or acids.
3) Glycosidation and the priority of glycoside formation:
a) O-glycoside at C-3 , C-7 , C4‟.
b) C-glycoside at C-6 or / and C-8.
Variation in the structure of flavone-derivatives:
77. A
B
C
1
2
3
4
5
6
7
8 1'
2' 3'
4'
5'
6'
Flavanonol
Flavan-3,4-diol
Anthocyanidin
D
e
h
y
d
r
o
g
e
n
a
t
i
o
n
-2 H
Oxidation
1) Reduction, + 4 H
2) Dehydration, - H2O
O
Dehydration, - H2O
in acid medium, + HX
Partial Reduction
+ 2 H
Dehydrogenation
- 2 H
Flavanone
O
O
Chalcone
OH
O
O
OH
O
C
Flavone
O
O
C
Flavan-3-ol
Catechin
O
OH
C
O
OH
C
Flavonol
O
OH
O
C
O
OH
OH
C
X
Ring closure
Different classes of flavonoids according to oxidation pattern of ring C
78. Isolation:
The extraction is usually affected by methanol, ethanol or water, and then
flavonoids are purified by:
• Extraction into alkaline solution(?).XXXXX
• Precipitation by lead acetate. XXXXXX
• The different classes are generally separated by column chromatography
using silica gel or polyamide.
• Paper chromatography can be used for separation and for identification.
Color test for flavonoids
1) Aluminum chloride test:
They give yellow color which fluoresces under UV with different colors.
Flavones................. Green.
Flavonols............... Yellowish to Yellowish-green
Chalcones............... Brown-pink.
Aurones.................. Pale brown.
2) Shinoda‟s test:
Alcoholic solution of flavanone or flavonol gives with Mg metal and
HCl, an orange, red or violet color.
3) An alcoholic solution of chalcones gives with antimony pentachloride
(SbCl5) in carbon tetrachloride (CCl4), a red or violet color or precipitate.
The test is negative with flavanone, flavone and flavonol.
79. • Color in visible light.
• UV: all are visible in UV except flavane.
• UV and fuming with ammonia.
• AlCl3-spary increases intensity of color and fluorescence in UV.
• Gas chromatography (GC) after silylation or methylation.
Estimation of Flavonoids:
• Colorimeter.
• Spectrophotometer.
Summary for the methods of detection
for flavonoids:
80. Structure determination:
•Acid degradation of glycoside: aglycone and sugars.
•Alkaline degradation with alcoholic potassium hydroxide:
Ring A Phenols.
Ring B Substituted benzoic acid.
KOH
Phenol Drivative Benzoic acid Derivative
Alkaline degradation
A
A
B
C
1
2
3
4
5
6
7
8 1'
2' 3'
4'
5'
6'
Flavone Derivative
O
O
HO
OH
R2
R1
R3
HO OH
OH
B R2
R1
R3
HOOC
•UV spectra: Two strong absorption bands at:
a) ca. 250 nm. b) ca. 300 - 350 nm.
c) Addition of alkali causes “Bathochromic shift”,
i.e. shift to longer wavelength.
•Infra red spectra (IR): They show the following:
1)Absorption band at 1620 cm-1 due to carbonyl-group (C=O) for compounds
containing hydroxyl-group at C-3.
2)Absorption band at 1650 cm-1 due to (C=O) for compounds containing
hydroxyl-group at C-5. This is due to strong hydrogen bonding between
carbonyl oxygen and hydroxyl-groups at C-3 or C-5.
•Mass spectrometry.
•Proton and 13C-NMR
81. Flavanone
Eriodictyol R1 = R2 = OH
Hespiritin R1
= OH , R2
= O-CH3
Naringenin R1 = H , R2 = OH
Flavone
Apigenin R = H
Luteolin R = OH
Flavonol
Kaepferol R1 = R2 = H
Quercetin R1
= OH, R2
=H
Myricetin R1 = R2 = OH
Catechin
Catechin R = H
Gallocatechin R = OH
Anthocyanidin
Cyanidin R = H
Delphinidin R = OH
Isoflavonoid
Forrononetin R1 = O-CH3 , R2 = H
Genistein R1
= R2
= OH
1
2
3
4
5
7
1'
3'
4'
O
O
HO
OH
R2
R1
1
2
3
4
5
7
1'
3'
4'
O
O
HO
OH
OH
R
1
2
3
4
5
7
1'
3'
4'
5'
O
O
HO
OH
OH
R1
R2
1
2
3
4
5
7
1'
3'
4'
5'
O
HO
OH
OH
OH
R
1
2
3
4
5
7
1'
3'
4'
5'
O
HO
OH
OH
OH
R
1
2
3
4
5
7
1'
3'
4'
5'
O
O
HO
R2
R1
OH OH
OH
Some examples
of
flavonoid
aglycones
82. Classification of flavonoid glycosides
i. Flavone glycosides.
ii.Flavonol glycosides.
iii.Flavanone glycosides.
iv.Isoflavonoid glycosides.
v.Chalcone glycosides.
vi.Anthocyanidins and their glycosides.
vii.Catechins and oligomeric Proanthocyanidins.
viii.Flavonolignan.
83. 1
2
3
4
5
7
1'
3'
4'
O
O
O
OH
OH
D-Apiose(1 6)---D-Glucose
Apigenin
(5,7,4'-Trihydroxy-flavone)
Apiin
(5,7,4'-Trihydroxy-flavone-7-O-glucoapioside)
CHO
C
C
H OH
OH
CH2
OH
HOH2C
Apiose
i) Flavone glycosides
1) Apiin: XXXXXX
Leaves and seeds of parsley (Apium petroslinum) and celery (Apium
graveolens) Fam. Umbelliferae.
Ray florets of Compositae.
Apiin occurs in colorless needles m.p. 2360C., difficult soluble in cold
water or methanol, but soluble in hot. Apiin solution is dextrorotatory.
The glucoapiose residue is attached at position 7, i.e. C-7.
Apiin solution gives with ferric chloride a reddish-brown color.
Apiin is hydrolyzed with emulsin or mineral acids to give apiose, glucose
and apigenin.
By a controlled hydrolysis process using 1% HCl, it yields apiose and & 7-
gluco-apigenin. This indicates that apiose is the terminal sugar.
85. ii) Flavonol glycosides
-D-Glucose-(1 6)-L-Rhamnose
Quercetin Rutinose
Quercetin-3-glucoside
Rutin
1
2
3
4
5
7
1'
3'
4'
5'
O
O
HO
OH
OH
OH
O
oIsolation from plants:
Extract by boiling 80% ethanol, evaporated and filtered.
Extract the filtrate with ether. Concentrate the aqueous solution, allow to stand.
Rutin is crystallized out. Purified by column chromatography (silica gel / ethanol.
Pale yellow needles, nearly insol. in water, fairly sol. in alcohol and insol. in
ether.
oThe sugar residue is linked at position 3 (at C-3 hydroxyl-group).
oQuercetin is 5, 7, 3‟, 4‟-tetrahydroxy-flavonol.
o Also it could be named as 3, 5, 7, 3‟, 4‟,-pentahydroxy flavone.
• Uses: Capillary bleeding (decreases capillary fragility and capillary
permeability).
1) Rutin:√√√
• Leaves, stems, buds and seeds of
numerous plants. Examples:
Leaves of Ruta graveolens L.
Fam. Rutaceae.
Buds of sophora japonica Fam.
Leguminosae (20%).
86. 2) Quercitrin:XXXX
L-Rhamnose
Quercetin
Quercitrin
(Quercetin-3-rhamnoside)
1
2
3
4
5
7
1'
3'
4'
5'
O
O
HO
OH
OH
OH
R2
O
• On hydrolysis, it gives rhamnose and quercetin (aglycone).
• Isolation: The same procedure as rutin
Other less important flavonol glycosides are: hyperoside, quercimeritrin
and spiraoside.
• Bark of Quercus tinctoria and other
species of Quercus .
• Vitis vinifera and in many others.
• White scaly crystals.
• Sparingly soluble in water.
•Quercitrin + basic lead acetate yellow
precipitate, which dissolves in excess.
• It shows a brown fluorescence under UV.
Tests for identity for rutin:
• Rutin + lead acetate Yellow precipitate.
• Solution of rutin + FeCl3 Greenish-brown color.
oOn hydrolysis, rutin Rhamnose, glucose and quercetin.
87. iii) Flavanone glycosides
• Colorless, tasteless, needle-shaped crystals, m.p. 256 0C.
• Sparingly soluble in water and in alcohol, more in hot, insol. in ether.
• Hydrolysis by acid Rhamnose, glucose and hesperitin (aglycone).
• Hesperitin is 5, 7, 3’-trihydroxy-4’-methoxy-flavanone.
Hesperidin:
• Rind of unripe,
green citrus fruit
e.g. bitter orange
(Citrus aurantium),
sweet orange
(C. sinensis),
lemon (C. limonis) citron (C. medica).
• Alkali (NaOH): Ring C opening Hesperidin chalcone which could be
stabilized by methylation.
• Hesperidin could be regenerated from hesperidin chalcone by action of acid.
88. • Hesperidin is necessary for the absorption of vitamin C.
Use:
In combination with vitamin C to reduce capillary permeability and fragility; usually
in cases of habitual abortion, hemorrhagic nephritis, hypertension and in cerebro-
and cardio-vascular diseases.
Other flavanones of less importance are naringin and citronin.
Rutinose
Alkali (NaOH)
Acid (HCl)
1
2
3
4
5
7
1'
3'
4'
O
O
O
OH
OCH3
OH
Rutinose
4
5
1'
3'
4'
ONa
O
O
OH
OC
H3
OH
1
2
6
iv) Isoflavone Glycosides
----------
Isoflavone is derived from 3-phyenylchroman. The first natural isoflavone isolated
was iridin, a glucoside of irigenin, from the rhizomes of Iris florentina.
Other isoflavones are genistein as examples for the aglycones, while sophoricoside
as examples for glycosides.
91. v) Chalcone and dihydrochalcone
• Few in nature. Absence of pyrane ring.
• The hydroxylation Similar to flavonoids. OH-group is present at (2).
• Conversion of chalcones to flavanones occurs in acid and reverse in base.
• Acid hydrolysis of chalcone glycoside Flavanone aglycone as artifact.
+ Glucose
H+
1
6
Carthamin
3
4
5
2
1'
3'
4'
OH
O
HO
OH
OH
O Glucose
1
6
4
5
2
1'
3'
4'
OH
O
HO
OH
OH
OH
1
2
1 2
Ring closure Ring closure
[Chalcone]
Carthamidin
5, 7, 8, 4'-Tetrahydroxy-flavanone
Iso-carthamidin
5, 6, 7, 4'-Tetrahydroxy-flavanone
1
2
3
4
5
7
1'
3'
4'
O
O
HO
OH
OH
OH
1
2
3
4
5
7
1'
3'
4'
O
O
HO
OH
OH
HO
1
2
When ring closure is between OH group at C(6) and carbon atom ()
When ring closure is between OH group at C(2) and carbon atom () due to bond rotation
92. vi) Anthocyanidins and their glycosides
Cyanin
1
2
3
4
5
7
1'
3'
4'
O
HO
O
OH
O
Glucose Glucose
OH
Cyanidin chloride
1
2
3
4
5
7
1'
3'
4'
O
HO
O
OH
OH
Glucose
OH
Cl
• Anthocyanidins: Related to the flavone. The glycosides anthocyanins.
• The name: Greek word “antho-” (= flower), and “kyanos” (= blue).
• Sap pigments and the actual color of the plant organ is determined by the pH of
the sap. The blue color of the cornflower and the red color of roses are due to the
same glycosides. On acid hydrolysis cyanidin hydrochloride.
• Precipitated from aqueous solution as lead salts (blue color) or as picrates.
• Sugar components:At 3- or rarely 5- position as Monosaccharide, Disaccharide
or Tri-saccharide.
• Diglucoside: At both 3 and 5.
93. A) Catechins:
•There are three type of catechin differing in the number of OH-groups in
ring B and having two asymmetric carbons (2 & 3) i.e. optically active.
• Catechins have [H] at 2 & 3 as trans while in epi-catechin they are cis.
•Test for catechin: On heating with acid Phloroglucinol.
Phloroglucinol can be detected by a modified test for lignin.
A match stick is dipped in the plant extract, dry, moisten with conc.HCl and
warm. The phloroglucinol produced turns the wood pink or red.
vii) Catechins and Oligomeric Proanthocyanidins
(+)-Catechin R = H
(+)-Gallocatechin R = OH
1
2
3
4
5
7
1'
3'
4'
O
HO
OH
OH
OH
OH
R
5'
H
H
A
B
(-)-Epicatechin
1
2
3
4
5
7
1'
3'
4'
O
HO
OH
OH
H
OH
OH
H
A
B
94. B) Proanthocyanidin:
• Proanthocyanidin are compounds forming anthocyanidins on heating with
acid. They are subdivided into three classes:
1) Leucoanthocyanidin:
Monomeric flavan-3, 4-diols.
Water soluble pigments.
Closely related to anthocyanidin.
Converted to anthocyanidin when
boiled with aqueous or alcoholic HCl.
HCl
Cl
O
OH
OH
O
OH
2) Dimeric compounds:
•On heating with acid one molecule of catechin + one of anthocyanidin
Both C-C and C-O bonds are present in these dimers.
• Trimers of this type are known and some are esterified with gallic acid.
Cyanidin chloride
1
2
3
4
5
7
1'
3'
4'
O
HO
O
OH
OH
Glucose
OH
Cl
96. VI) Phenolics consisting of C6-C3-C6-C3- C6: Flavolignans or Ligno-flavons.
viii) Flavonolignans
• New group of natural substances.
• Structure: A flavonol and a lignan (hemi-lignan = C9
fragment) condensed together by oxidative combinations.
• They have anti-hepatotoxic properties, and extract of plants
containing them are widely used for treatment of liver diseases.
• Fruits of Silybum marianum (Fam. Compositae) contain:
1- Silybin.
2- Silydianin.
3- Silychristin.
4- Isosilybin.
5- Silandrin.
6- Silymonin.
All are consisting of the
flavonoid taxifolin and dihydroconiferyl alcohol.
O
O
O
OCH3
OH
HO
O
OH
CH2OH
OH
1
Silybin.
97. Cyanophore Glycosides
cyanogenetic glycosides
Definition:
Glycosides which on hydrolysis yield HCN as one of the products.
• Common present in Rosaceous plants.
• Many are derived from mandelonitrile (benzaldehyde cyanohydrin).
• They contain nitrogen but the glycoside is of O-glycoside type.
• Sugar part may be a monosaccharide or a disaccharide such as gentiobiose.
• In case of disaccharide, the hydrolysis by enzymes takes place in two steps and the
liberation of HCN occurs by a secondary reaction of the aglycone.
• Principle of these tests is the reaction between HCN as hydrolysis product with
different reagents.
1) A section, made in plant, is: P
a) Placed in alcoholic KOH for one minute.
b) Transferred to a solution of 2.5% ferrous sulfate and 1% of ferric chloride.
Section is kept at 60 0C for about 10 minutes.
c) Transferred to 20%HCl.
•HCN acid is indicated by: Formation of Prussian blue Fe4[Fe(CN)6]3 Ferric
ferrocyanide.
•Reduction of mercurous nitrate (3%) to metallic mercury (Hg).
Detection of Cyanophore glycosides (in plants):
98. 2) Picric acid paper:
In presence of HCN the paper is turned from yellow into brick red.
o Picric acid paper is prepared by soaking paper in 1% aqueous picric acid
solution, drained, and then soaked in 10% sodium carbonate solution,
drained and dried.
o The paper is hanged in a flask containing the drug under examination
moistened with water. The brick-red color is due to the formation of
sodium iso-purpurate.
99. 1)Amygdalin
-D-Glucose-(1 6)--D-glucose
Benzaldehyde-
cyanohydrin
Prunasin
Amygdalin
C
CN
H
O
Preparation:XXXXXXXXX
1)Fixed oil is firstly expressed from the seeds.
2)Extract the cake with 95% alcohol, concentrate, then mixed with large volume of
ether. Amygdalin crystallizes out.
Hydrolysis:
o Total hydrolysis gives two molecules of glucose, benzaldehyde and HCN.
o Controlled hydrolysis takes place by three enzymes in 3 steps:
1) Amygdalase: One mole glucose + One mole mandelonitrile glycoside.
2) Prunase: Second mole glucose + one mole mandelonitrile.
3) -Hydroxy-nitrilase: Mandelonitrile HCN + benzaldehyde.
o Emulsin obtained from almond kernel contains enzymes amygdalase
and prunase.
• It is the most widely
distributed of cyanophore
glycosides.
• Seeds of Rosaceae; e.g.
bitter almond, Prunus
amygdalus, var. amara.
100. Acetone-cyanohydrin-glycoside present in Linseed.
C O
H3
C
CN
CH3
-D-Glucose
Hydrolysis:
On hydrolysis, it gives glucose, acetone and HCN.
N.B.:
During the preparation of linseed oil, we have to get off HCN
from the oil by boiling the fixed oil by means of superheated steam
(bubbling in the oil), so that any traces of HCN are removed.
Linamarin
)
2
101. • Other names: Thiocyanate or sulfurated glycosides (Glucosinolates).
• Abundant in the Cruciferae (Brassicaceae)
1)The general formula:
R C
S
N O SO2-O-K
-D-Glucose
• On hydrolysis, all of them
1) Glucose 2) acid sulfate
3) variable compounds according to the aglycone present in the
glucosinolate itself.
Thioglycosides
The basic structure comprises:
Glucose residue as S-glucoside.
Sulfate group.
A variable aglycone [R].
o The molecule occurs as a sulfate salt [X].
The most important thioglucosides are:
Sinigrin, Sinalbin and Glucotropaeolin
102. 1) Sinigrin (potassium myronate)
• Black mustard seeds ≈ 4%.
• Black mustard seeds and the glucoside sinigrin are revulsive due to the action of the
volatile allylisothiocyanat, which cause tingling, rubefaction and vesication of skin.
They are only used in food.
C
S
N O SO2-O-K
-D-Glucose
CH2 = CH - CH2
Glucose +
KHSO4 +
CH2 = CH - CH2 - N = C = S
[Allyl-iso-thiocyanate]
Myronase
+ H2O
Sinigrin
• Hydrolysis:
By enzyme myrosin (myrosinase) glucose, potassium acid sulfate and
allyl-iso-thiocyanate (Volatile oil “Mustard oil” with a pungent odor and taste.
• Sinigrin occurs in prisms or needles, soluble in water, insoluble in ether.
• Test for identity:
a) Allyl-isothiocyanate: Characteristic odor and taste.
b) Paper chromatography for the glycoside (sinigrin):
• Mobile phase : n-Butanol: Acetic acid: Water.
• Spray reagent : 1) Silver nitrate................ (AgNO3).
2) Potassium dichromate. (K2Cr2O7).
• Result:1) Background: Red (Ag2CrO4)
2) Glycoside : Yellow.
103. 2) Sinalbin
• White mustard seeds
•Sinalbin may cause pre-cancerous cells to dei (apoptosis). It has been suggested that
sinalbin may prevent cancer of the colon in case of regular eating food containing it.
C
S
N O SO2-O
-D-Glucose
CH2
HO
OH
O - CH3
O - CH3
N
CH3
CH3
H3
C
CH2-CH2- O - CO
Sinalbin
Sinapic acid
Choline
Sinapic acid choline ester
p-Hydroxybenzyl
Acid
Hydrolysis
or Enzyme "Myrosin"
(Myrosinase)
OH
O - CH3
O - CH3
N
CH3
CH3
H3C
CH2 - CH2 - O - CO
SO2-O
HO
+
Acid sulfate of Sinapic acid choline ester
p-Hydroxybenzyl-isothiocyanate
HO CH2 N C S + Glucose
• Hydrolysis: It yieldsAcrinyl-isothiocyanate,which has a pungent taste but odorless.
104. Biosynthesis of Triterpenoid Compounds:
• Parent compound of all triterpenoids, squalene, contains 30 carbon atoms.
• Squalene is derived from two farnesyl PP units, joined together in the
unusual „tail-to-tail‟ fashion.
• The polycyclic structures formed from squalene can be rationalized in
terms of the ways in which squalene may be folded (pseudo-chair and
boat conformations) on the enzyme surface, with due consideration
given to stereoelectronic requirements for cyclisation.
• Chair-Chair-Chair-Boat (CCCB)Pentacyclic and tetracyclic triterpenes
(Triterpenoid Saponins).
• Chair- Boat -Chair- Boat (CBCB) The tetracyclic triterpenes branch
forming steroid compounds. (Cholesterols, Sex hormones, Corticosteroids,
Cardenolide and the well known Steriodal saponins).
105.
106. The major types of triterpenoid compounds:XXXXXXXXXX
For all tetracyclic: The numbers 28 and 29 are reserved for α or β-methyl- and ethyl- at C(24).
Lanostane type Cycloartane type
Basic type of steroids (C30) -CH3 at C(13)]
3
14
13
H
H
H
H
10
4 5
9
8
17
18
19
20
21 22
25
26
27
30
31
32
8
5
1
15
11
12
3
14
13
H
H
H
10
4
9
17
18
19
20
21
25
26
27
1
24
1) Parent Nuclei for Steroidal Triterpenes
30 31
[A/B/C = T/T/T] [A/B/C = T/C/T}
24
Dammarane type Euphane type
-H at (C13)] -CH3 at (C13)]
OR
2) Parent Nuclei for Tetracyclic Triterpenes
3
14
13
H
H
H
10
4 5
9
8
17
19
20
21 22
25
26
27
30 31
32
1
15
11
12
24
H
3
14
13
H
H
H
10
4 5
9
8
17
19
20
21 22
25
26
27
30 31
32
1
24
H
-H at (C13)] -CH3 at (C13)]
107. 3
14
13
H
15
16
17
18
19
12
20 21
22
29
30
28
23 24 Oleanane type
Ursane type
10
4 5
9
27
8
25 26
1
H at C(13) and -CH3 at C(14)]
3) Parent Nuclei for Pentcyclic Triterpenes
11
H
H
H
3
14
13
H
17
18
19
20 21
22
29
30
28
23 24
10
4 5
9
27
8
25 26
1
H
H
H
[A/B/C/D = T/T/T/C] [A/B/C/D = T/T/T/C]
Lupane type Hopane type
3
14
13
H
17
18
19
20
21
22
29
30
28
23 24
10
4 5
9
27
8
25 26
1
H
H
H
3
14
13
H
17
18
19 20
21
22
29
30
28
23 24
10
4 5
9
27
8
25 26
1
H
H
H
[A/B/C/D
= T/T/T/T]
[A/B/C/D = T/T/T/T]
109. Cardio active Steroidal Glycosides
Definition:
“They are glycosidal constituents with therapeutic action on the insufficient
heart, when given in small doses, but a large dose may cause death.”
Plants containing cardiac glycosides have long been used as arrow poisons or
drugs. Cardio-active glycosides occur in plants in small amounts and in various organs.
Fam. Scrophulariaceae...... Leaves of Digitalis
Fam. Apocyanaceae ......... Seeds of strophanthus.
Fam Apocyanaceae........... Seeds of Strophanthus.
Fam. Runnunculaceae....... Leaves of Adonis.
Fam. Liliaceae ..................Scales of bulbs
of Urgina & Convallaria.
Structure:
Many of cardio-active glycosides have:
The same aglycone but with different
sugar residues.
Identical sugar residues but different
Aglycone (e.g. Digitoxin &
Gitoxin).
The aglycones are related chemically to
sterols & bile acids.
1
2
3
4 5 6
7
8
9
10
11
12
13
14
15
16
17
18
19 20
21
22
23
24
25
26 27
General Numbering of Steroid
A B
C D
HO
A B
C D
Phenanthrene
Cyclopentano-per-
hydrophenanthrene
110. Ring combination / Configuration / Conformation
A/B B/C C/D Description Example
Trans Trans Trans Cholesterane-series Cholesterol
Cis Trans Trans Koprostane-series Bile acids
Cis Trans Cis Cardenolide-series Digitoxin
14
19
5
18
1
3
8
9
17
Cholesterane series [Trans/Trans/Trans]
Koprostane series
[Cis/Trans/Trans]
Cardenolide series
[Cis/Trans/Cis]
A
B
C
D
R
R
9
18
19
1
3
8
5 14
17
Trans Trans Trans
A B
C D
R
9
18
19
1
3
8
5
14
17
R
Cis
Trans Cis
A
B
C
D
R
9
18
19
1
3
8
5
14
17
R
Cis
Trans Trans
A
B
C D
H
H
H
H
14
19
5
18
1
3
9
A
B
C
D
H
H
H
H
14
19
5
18
1
3
9
A
B
C
D
H
H
H
H
13
10
10
13
13
10
111. 17
1
2 3
14
5
18
1
3
9
A
B
D
H
H
C
1
O O
C17
20
21
22
23
O O
C17
20
21
22
23
24
General Cardiac glycosides structure:
1)Aglycone:
Steroidal, Tetracyclic skeleton,
Largely saturated.
A) Stereochemical configuration of the four fused rings: A / B / C/ D, as follows:
A / B B / C C / D
Cis Trans Cis
B) Essential groups for activity and their characteristics:
Unsaturated lactone ring in -position at carbon (17).
Hydrogenation of double bond or opening of ring leads to loss of activity.
2
3
OH-Group in -position at carbon (3).
OH-Group in -position at carbon (14).
112. Card-20(22)-enolide Bufa-20,22-dienolide “Scilladienolide”
1 Five member ring with 4 carbon
atoms & one oxygen atom.
Six member ring with 5 carbon atoms
& one oxygen atom.
2 One double bond. Two double bonds.
3 One active (CH2) No (CH2)
4 Referred as butenolide Referred as pentadienolide
Card-20(22)-enolide
17
14
5
18
1
3
9
R
H
H OH
HO
O O
20
21
22
23
17
14
5
18
1
3
9
R
H
H OH
HO
O O
20
21
22
23
24
Bufa-20, 22-dienolide
"Scilladienolide"
On the basis of lactone ring structure, the aglycone may be grouped into:
Cardenolides 2) Scilladienolides
The unsaturated lactone ring has the following characters:
113. 12
16
17
1
3
14
5
18
1
3
9
A B
D
R C
1
2
4
19
R1
R1=Unsaturated lactone ring.
1
2
3
Difference
in Aglycone
Number and position of other OH-groups at C (12), (16).
Variations in oxidation extend of C (19).
Digitalis CH3
Strophanthus -CH2OH or -CHO
Stereochemical differences. -C=C- , i.e. 4 Scilla
114. Bufo-toxins:
•They are secreted by the European toad, Bufo regularis.
•Similar pharmacological activity on the heart.
•They are steroid containing.
1)Pentadienolide lactone structure as scilladienolide.
2)A suberoylargenine is attached to OH-group at C (3).
3)A polypeptide chain may be present at C (3) instead of the
sugar.
H2N
C
NH
NH
HOOC
N
H
(CH2)8
O
O
O
Suberoylarginine moiety
115. •Sugar Components:
• One, two, three or four monosaccharide units linked through OH-group at C (3).
• With the exception of glucose, all are of the desoxy-type.
1)6-Desoxy-sugar.............. L-Rhamnose.
2)2, 6-Desoxy-sugar.......... D-Digitoxose.
3)3-O-Methyl-ether of 2, 6-desoxy-sugar: Digitalose, D-Cymarose and D-Diginose
CHO
CH3
L-Rhamnose
CHO
CH2
CH3
CHO
CH2
CH3
D-Digitoxose D-Cymarose
O-CH3
CHO
CH2
CH3
H3C-O
D-Diginose
D-Glucose
CHO
CH2
OH
CHO
H3
CO
CH2
OH
D-Digitalose
Sugar
6-De-oxy sugar 2,6-Dide-oxy sugar
Usual sugar
Convallaria
Scilla
Digitalis Digitalis Strophanthus Oleander
L-Mannose D-Glucose D-Allose or
D-Altrose
D-Galactose
or D-Talose
Type
Plant
Biosyntheic
origin
Many
• Pharmacological activity is due to the aglycone, but the sugars act through:
1)Increasing both potency and toxicity.
2)Effects on some physical properties such as solubility and consequently absorption
rate and transportation to site of action.
116. Biosynthesis of Aglycone:XXXXXXXXX
1
2
3
1 2 3 Acetyl-
Co-Enzyme A
Cholesterol 21-Hydroxy-20-oxo-pregnane
1
2
3
4
5
6
10
11
12
13
14
16
17
18
19 20
21
22
23
24
25
26 27
A B
C D
HO
H
1
2
3
4 5 6
7
8
9
10
11
12
13
14
16
17
18
19
20
21
A B
C D
H2C
HO
OH
O
OH
CH3
C O
SCoA
+
Cardenolide
+ HS Co A
+ H2O
+ 2 H
• Formation of 21-hydroxy-20-oxo-pregnane.
1) Splitting at C (20), C (22).
2) Oxidation at C (14) to give OH-group.
3) Reduction at C5 = C6 (Δ5).
21-Hydroxy-20-oxo-pregnane
Cardenolide
Bufodienolide
+ Oxaloylacetate
+ Acetate
• Cardenolides:By condensation with acetyl-Co-enzyme A (CH3-CO-S-Co A) to get
the five membered lactone ring.
• Scilladienolides: By condensation with oxaloyl-acetyl-Co-enzyme A (HOOC-
CO-CH2-CO-S-CoA) to get the six membered lactone ring, with subsequent
dehydrogenation to obtain a double bond at C-4, i.e. -C4=C5-.
117. active Steroidal
-
Identification Tests for Cardio
glycosides and their Aglycones
A) Test for Steroid Part of the Molecule:
•Liebermann test for Sterols:
Solution of glycoside or aglycone in glacial acetic acid + one drop of conc. sulfuric
acid. Red color Violet-Blue Green. (Characteristic for Scillarenin-type).
B) Test for unsaturated Lactone Ring:
1) Legal test:
Solution of glycoside or aglycone in pyridine + one drop of 2% sodium nitroprusside
+ one drop of 20% sodium hydroxide.
Deep red color (Characteristic for unsaturated lactone ring)
2) Baljet test:
Solution of glycoside or aglycone + Baljet reagent Red color
(Characteristic for unsaturated lactone ring).
Baljet reagent: Two parts (1) and (2), which must be mixed immediately before use:
(1) 1% aqueous solution of picric acid.
(2) 10% aqueous solution of sodium hydroxide.
118. C) Cardenolide test “test for active methylene-group (CH2):
1) Raymond‟s test:
Alcoholic solution of glycoside or aglycone + 0.1 ml of 1% solution m-dinitobenzene
in ethanol + 2 - 3 drops of 20% sodium hydroxide Violet color Blue.
(Characteristic for active methylene-group).
2) Kedde‟s test:
Glycosides or aglycones + Kedde‟s reagent Blue or violet color fades in 1-2 hrs
(Characteristic for active methylene-group).
Kedde‟s reagent: Mixing equal volumes of:
1) 2 % Dinitrobenzoic acid in methanol.
2) 5.7 % aqueous potassium hydroxide.
N.B: Kedde’s reagent is also used to spray chromatograms.
D) Test for 2-Desoxysugar:
1) Keller-Kiliani test:
Glycosides in glacial acetic acid containing FeCl3 + Sulfuric acid containing FeCl3.
Intense blue color at the interface between two layers Spreading into
the glacial acetic acid layer. (Characteristic for 2-desoxy-sugar).
1) Xanthohydrol test:
Heating the glycoside with solution of xanthohydrol (0.125%) + HCl (1%) in glacial
acetic acid Red color (Characteristic for 2-desoxy-sugar).
119. O
O
A B
C D
1
3
5
7
9
11
12
14
17
18
19
20
21
22
23
Cardenolides
A B
C D
1
3
5
7
9
11
12
14
17
18
19
21
O O
20
22
24
Bufadienolides
O
Digitoxose_Digitoxose_Acetyl Digitoxose_ D Glucose
Liebermann’s test
Antimony
trichloride
Legal’s test
Baljet’s test
Raymond’s test
Kedde’s test
Keller-Kiliani’s test
Xanthydrol test
Identification Tests for Cardio-active
Steroidal glycosides and their Aglycones
120. A) Acid hydrolysis: Hydrolysis with acids affords aglycone and sugar or sugars.
After hydrolysis, neutralized by Na2CO3solution and extract with chloroform.
• Chloroform contains aglycone (test for aglycone).
• Aqueous layer contains sugar or sugars, evaporate, extract with pyridine and identify
the sugar using TLC and specific spray reagent, or test for the sugar in the aqueous
solution directly.
Hydrolysis of Cardio-active Glycosides
KOH
KOH
B) Action of Alkali:
1) Mild alkaline hydrolysis removes the ester group. Examples:
Lanatoside A Purpurea glycoside A + Ac.O.K
Lanatoside B Purpurea glycoside A + Ac.O.K
2) Strong Alkali Solution:
It leads to opening of lactone ring attached to C (17).
When lactone ring is opened, it does not reform to yield the original lactone
ring, but it forms another lactone with another OH-group in other part of the
aglycone leading to deactivation.
121. B) Enzymatic hydrolysis:
In plants, the enzymes can split the glycoside into sugar and secondary
glycoside. Examples are:
1) Enzyme digilanidase: It removes the terminal sugar, i.e. Glucose, as follows:
Lanatoside A Glucose + Acetyl-digitoxin.
Purpurea glycoside A Glucose + Digitoxin.
Generally: Primary glycoside Glucose + Secondary glycoside.
2) Enzyme Strophanthobiase:
K-Strophanthin B
Glucose + Cymarin.
3) Yeast Enzyme:It removes the terminal -glucose from K-strophanthoside
K-Strophanthoside Glucose + K-strophantin B.
Yeast Enzyme
122. CARDIAC GLYCOSIDES HYDROLYSIS:
1-Acid Hydrolysis
2- Alkaline hydrolysis
A- Deacetylation in sugar
B- Lacton opening
O
O
D
14
OH
O
O
D
14
OH
H OH
OH
O
O
OH
OH
H+
Active
3- Enzymatic hydrolysis
Remove the terminal sugar (Glucose)
Digilanidase for digitalis glycoside
Yeast enzyme for straphanthus glycoside
Strophanthobiase for straphanthus glycoside
124. Uses:
1) Heart insufficiency.
2) Diuretic, the most active in this respect is scillarin.
3) The aglycones have the same pharmacological action as the glycosides do, but
they are not medically used due to insolubilities.
4) Expectorant (white squill).
5) Rat poison (red squill).
Standardization:
a) Bioassay:
By determining the amount of drug necessary to stop the heart of a given
animal under specified conditions.
Animals used are: Frog, Pigeon, Cat, Guinea pigs.
b) Chemical methods:
•Qualitative: (1) Lactone ring: “Kedde, Baljet ... etc.”
(2) 2-Desoxy-Sugar: “Keller-Kiliani,...etc.
•Quantitative: (1) Baljet reaction “Colourimetry”.
(2) Semi-quantitative by TLC.
125. 1) Digitalis leaves: D. purpurea, D. Lanata.
2) Strophanthus Seeds: S. Komb , S. Gratus.
3) Squil bulb:
a) White squil, Urginea maritima (white variety).
b) Red squil, Urginea maritima (red variety).
Glycoside Aglycone Digitoxose Glucose Digitalose
Purpurea glycoside A Digitoxigenin 3x 1x -
Digitoxin Digitoxigenin 3x - -
Odorside H Digitoxigenin - - 1x
Purpurea glycoside B Gitoxigenin 3x 1x -
Gitoxin Gitoxigenin 3x - -
Strospeside Gitoxigenin - - 1x
Digitalinum verum Gitoxigenin - 1x 1x
Glucogitaloxin Gitaloxigenin 3x 1x -
Gitaloxin Gitaloxigenin 3x - -
Glucoverodexin Gitaloxigenin - 1x 1x
Verodexin Gitaloxigenin - - 1x
Glycosides of Digitalis purpurea
:
Crude Drugs
127. Genins of Digitalis Glycosides
OH
H
3
14
17
O O
HO
12
16
OH
H
3
14
17
O O
HO
12
16
OH
H
3
14
17
O O
HO
12
16
OH
H
3
14
17
O O
HO
12
16
OH
H
3
14
17
O O
HO
12
16
OH at 16
OH at 12
O
H
a
t
1
2
O
CHO
OH
OH
OH
OH
Both D. purpurea and D. lanata Only D. lanata
Digitoxigenin (A) Gitoxigenin (B)
Digoxigenin (C)
Diginatigenin (D)
Gitaloxigenin (E)
OH at 16
+ Formyl-Group
128. OH
H
3
14
17
O O
O
12
16
Digitoxigenin
Digitoxose - Digitoxose - Digitoxose - Glucose
Digitoxin
Purpurea Glycoside A
Digitoxose - Digitoxose - Acetyldigitoxose - Glucose
Acetyldigitoxin
Lanatosiode A
The same can be drawn
for
the other glycosideswhen:
•OH at C (12):
•OH at c (12):
•OH at C (12) & C (16):
•O-CHO at C (16)
129. I) Digitals Glycosides
Digitalis purpurea:
1) Primary glycosides:
- Purpurea glycoside A………. Chief Constituents of fresh leaves.
- Purpurea glycoside B
- Glucogitaloxin.
2) Secondary glycosides
- Digitoxin.
- Gitoxin Chief Constituents of dried leaves.
- Gitaloxin (=16 Formyl-gitoxin)
On hydrolysis with mineral acids, they give digitoxigenin, gitoxigenin
and gitaloxigenin as aglycones, respectively.
3) Saponin:Digitonin, gitin and digit-saponin
Lanatoside A
Lanatoside B
Lanatoside C
Lanatoside D
Lanatoside E
Enzyme Hydrolysis
- Glucose
Acetyl-Digitoxin
Acetyl-Gitoxin
Acetyl-Digoxin
Acetyl-Diginatin
Acetyl-Gitaloxin
Digitoxigenin
Gitoxigenin
Digoxigenin
Diginatigenin
Gitaloxigenin
Digitoxin
Gitoxin
Digoxin
Diginatin
Gitaloxin
Mild
Alkaline
Hydrolysis
- Ac
Further Hydrolysis
-3 Digitoxose
Digitalis Lanata:
It is three times potent
as D. purpurea.
It contains:
130. Some glycosides of Digitalis:
1) Digitoxin:
Secondary glycoside produced by hydrolysis of Purpurea glycoside A, or
Lanatoside A. It presents 0.2 - 0.4% of the dry leaf.
White, odorless micro-crystalline powder, slightly soluble in water and ether.
It shows the greatest cumulative action.
2) Gitoxin:
• Secondary glycoside from purpurea glycosides B and lanatoside B.
3) Digoxin:
• Secondary glycoside from lanatoside C.
Remarks:
• Gitaloxigenin differs from gitoxigenin by one formyl group at C (16).
• Glycosides containing digitalose are present in minute amounts. e.g., Verodoxin
(gitaloxigenin + digitalose).
• Digitalinum verum gives on hydrolysis glucose and a glycoside known as
strospeside, which is composed of gitoxin as aglycone and digitalose.
131. II) Strophanthus glycosides
(Glycosides obtained from strophanthus komb and S. gratus, Family Apocynaceae)
A) Stophanthus Kombé Glycosides:
Seeds of Strophanthus Kombé contain 8 - 10% K-strophanthin (Mixture).
General structural groups:
CH3
R
OH
OH
3
14
17
O O
O
12
16
Sugar components
Aglycone part
No Group R Example
1 Strophanthidin glycoside - CHO K-Strophanthoside
2 Strophanthidiol glycoside - CH2OH Cymarol
3 Periplogenin glycoside - CH3 Periplocymarin
No. Sugar Component(s) Glycoside Name
1 O-β-D-Cymarose-O-β-D-Glucose-O-α-D-Glucose K-Strophanthoside
2 O-β-D-Cymarose-O-β-D-Glucose K-Strophanthin B
3 O-β-D-Cymarose Cymarin
Example: Strophanthidin glycoside group: R = - CHO
The most important group is the group (1). The Aglycone contains:-
•Three OH at C 3 / 5/ 14.
•At C (10), the C (19) is an aldehyde.
•The sugars are -cymarose, -glucose and -glucose.
132. Properties:
•Very soluble in water, insoluble in chloroform.
•It is poorly absorbed when given orally; it is used as i.v. in emergency cases.
Chemical tests:
•Strophanthin + cold 80% sulfuric acid Emerald green color.
Ouabain Pink Brown red with green fluorescence.
•Strophanthin solution + one drop of ferric chloride + few ml of sulfuric acid,
Red precipitate Green in two hours.
•Strophanthin solution + tannic acid Precipitate.
1) K-Strophanthoside K-Strophanthidin + Trisaccharide.
(Trisaccharide = D-Cymarose-O--D-Glucose-O--D-Glucose)
2) K-Strophanthin B K-Strophanthidin + Strophanthobiose.
Enzymatic hydrolysis:
1) - glycosidase “Yeast”
K-Strophanthoside -Glucose + K-Strophanthin B
2) Strohanthobiase:
K- strophanthin B Cymarin and -Glucose
Strophanthobiose is a disaccharide consisting of “D-Cymarose-O-β-D-Glucose”
Acid hydrolysis:
133. B) Strophanthus gratus Glycosides:
Seeds of Strophanthus gratus contain 4 – 8 % total glycosides, of which 90–95 % is
G-strophanthin “Ouabain”. CH3
R
OH
OH
3
14
17
O O
O
12
16
-L-Rhamnose
Aglycone part
HO
1
OH
R = CHOH
It contains in its aglycone:
1) Five OH-groups at C 1 / 3 / 5 / 11
and 14.
2) At C (10), the carbon (19) is
a hydroxymethyl group (CH2OH).
Properties: Odorless, colorless, crystalline powder with bitter taste, soluble in cold
water and insoluble in chloroform.
G-Strophanthin = Ouabain = Ouabagenin-
α-L-ramnoside (Where R = CH2OH).
Chemical tests:
1)80 % sulfuric acid Pink color Brown-red color with Green fluorescence.
Strophanthin Emerald green color.
2)A solution + ammonium molybdate, evaporate. Cool the residue + conc. sulfuric
acid Blue color. (Froehde‟s reagent).
3)A solution + ammonium vanadate, evaporate. Cool the residue + conc. sulfuric
acid Green color. (Mandalin‟s reagent).
Hydrolysis: Ouabain Ouabagenine + L-Ramnose
134. Squill Glycosides
Squill bulbs are obtained from Urginea martitima, Fam. Liliaceae’
There are two varieties of squill; namely, the white variety and the red one.
A) Glycosides of the white variety of squill:
Two glycosides: “Scillarin A” is crystalline, & “Scillarin B” is amorphous.
17
14
5
18
1
3
CH3
CH3
OH
O
O O
20
21
22
23
24
4
19
-L-Rhamnose-O--D-Glucose--D-Glucose
Glucoscillarin A
Scillarin A
Proscillaridin A
• Scillarin A in the white variety of squill
is ca. 0.06 %.
• It is a white odorless microcrystalline
powder with a bitter taste.
• Its aglycone of scillarin A is scillaridin.
• Glucosidation is at OH-group at C (3)
• The aglycone "scillaridin" has::
• Two OH-groups at carbon (3) and (14),
• The lactone ring at carbon (17) is
six- membered, with two double bonds (-pyrone).
• A double bond between C4=C5. 4
Chemical test:
Scillarin + acetic anhydride + conc. sulfuric acid Blood red color
Blue Bluish-green.
135. Scillarin A Scillaridin + Scillibiose
Glucose + Rhamnose
Dil. Acid
Acid
Scillarin A Proscillaridin A + Glucose
Scillaridin A + Rhamnose
Scillarinase
Acid
Acid hydrolysis:
Enzymatic hydrolysis:
B) Glycosides of red variety of squill:
17
5
18
1
3
CH3
CH3
OH
O
O O
20
21
22
23
24
4
19
-D-Glucose
O
OH 14
CH3
C
O Scilliroside
• The aglycone is known as scillarosidin.
• It contains the following:
1) Four OH-groups at 3 / 6 /8 and 14.
2) Lactone at C-(17) is six membered
with two double bonds (-pyrone).
1) Double bond between C4=C5. 4
Use: As rat poison.
