2 GlycosidesDefinition:Glycosides are (usually) non-reducing compounds, on hydrolysis by reagents or enzymes yield one ormore reducing sugars among the products of hydrolysis. non-sugar glycosidic sugar linkage (genin) (glycone)1- Alcoholic or phenolic (aglycone): e.g., O-Glycoside CH2 OH CH2OH OH O-C6 H11 O5 C6 H12 O6 + -H2O Glycosidic linkage Sugar Salicin2- Sulphur containing compounds: e.g., S-Glycoside Glycosidic linkage SH S C6 H11 O5C 6H12 O6 + CH2 CH CH2 C CH2 CH CH2 C N OSO3 K Sugar N OSO3 K Sinigrin3- Nitrogen containing compounds: e.g., N-Glycoside
3 NH2 NH2OHCH2 O OH N N N N H + H N N N N OH OH H OHCH2 O Glycosidic linkage H H OH OH Adenine4- C-Glycoside HO O OH HO O OHC6 H12 O6 + CH2 OH CH2 OH Glycosidic linkage C6 H11 O5 Barbaloin1- Sugars exist in isomeric α and β forms. Both α and β Glycosides are theoretically possible.2- All natural glycosides are of the β Type.3- Some α linkage exists in sucrose, glycogen and starch. Also the glycoside K-strophanthoside (strophanthidin-linke to strophanthotriose (Cymarose + β-glucose + α- glucose).4-1- According to the type of glycosidic linkage: α- glycoside (α-sugar) and β-glycosides (β-sugar).2- According to the chemical group of the aglycone involved into the acetal union:a. O-glycoside (OH group)b. S-glycoside (SH group).c. N-glycoside (NH group).d. C-glycoside (C group).3- According to the nature of the simple sugar component of the glycoside:a. Glucosides (the glycone is glucose).
4b. Galacosides (the glycone is galacose).c. Mannosides (the glycone is mannose).d. Arabinosides (the glycone is arabinose).4- According to the number of the monosaccharides in the sugar moiety:a. Monoside (one monosaccharide) e.g., salicin.b. Biosides (two monosaccharide) e.g., gentobioside.c. Triosides (three monosaccharide) e.g., strophanthotriose.5- According to the physiological or pharmacological activity ‘therapeutic classification)a. Laxative glsycosides.b. Cardiotonic glycosides.6- according to the correlation to the parent natural glycoside:a. primary glycosides e.g., amygdalin, purpurea glycoside A,b. Secondary glycosides e.g., prunasin, digitoxin.7- According to the plant families.8- According to the chemical nature of the aglycone:a. Alcoholic and phenolic glycosides (aglycones are alcohols or phenols)b. Aldehydic G (aglycones are aldehydes).c. Cyanogenic G (aglycones are nitriles or derivatives of hydrocyanic acid).d. Anthracene or anthraquinone G (aglycones are anthracene der.).e. Steroidal G (aglycones are steroidal in nature, derived from cyclopentanoperhydrophenanthrene) .f. Coumarin G (aglycones are derivative of benzo α-pyrone).g. Chromone glycosides (aglycones are derivatives of benzo-δ-pyrone)h. Flavonoidal G (aglycones are 2-phenyl chromone structure).i. Sulphur containing or thioglycosides (aglycones are contain sulphur).j. Alkaloidal glycosides (aglycone is alkaloidal in nature) e.g., glucoalkaloids of solanum species.Sugars in glycosides:1- Monosaccharide (glucose in salicin, rhamnose in ouabain)2- Disaccharides (gentiobiose in amygdalin).3- Trisaccharides (strophanthotriose).4- Tetrasaccharides (purpurea glycosides)
55- Rare sugers (deoxy sugers)6- Sugar linked in one position to the aglycone rarely in 2 positions as sennosides.A- 6-deoxy sugarse.g., 1- methylpentoses 2- α-L-rhamnose. CHO H C OH O OH HO CH3 H C OH HO C H HO C H CH3 OH OHB- 2,6-deoxy sugars (called rare sugars)e.g.,1- D.digitoxose 2- D.cymarose 3- diginose CHO CHO CHO C H2 C H2 C H2 C OH C OCH3 H3 CO C C OH C OH HO C C OH C OH H C OH CH3 CH3 CH3C- 2-deoxy sugars e.g. 2-deoxy-D-ribose HOH2 C O H H OH OH H
6Characteristic of 2-deoxy sugers:1- Give positive Schiff’s test for aldehydes.2- Positive Keller-Kelliani test.Diversity in structure makes it difficult to find general physical and chemical properties:1- A- Most glycosides are water soluble and soluble in alcohols.B- Either insoluble or less soluble in non polar organic solvents.C- More sugar units in a glycoside lead to more soluble in polar solvents.2- Glycosides do not reduce Fehling’s solution, but when are susceptible to hydrolysis give reducingsugars (C-glycosides are exceptions).1- Acid hydrolysis:a- Acetal linkage between the aglycon and glycone more unstable than that between two individualsugars within the molecule.b- all glycosides are hydrolysable by acids non specific (except C-glycosides).c- Glycosides containing 2-deoxy sugars are more unstable towards acid hydrolysis even at roomtemperature.d- C-glycosides are very stable (need oxidative hydrolysis).2- Alkali hydrolysis:1- mild alkali2- strong alkali3- Enzyme hydrolysis:1- Enzymatic hydrolysis is specific for each glycoside there is a specific enzyme that exerts ahydrolytic action on it.
72- The same enzyme is capable to hydrolyze different glycosides, but α and β sterio-isomers of thesame glycoside are usually not hydrolysed by the same enzyme.3- Emulsin is found to hydrolysed most β-glycoside linkages, those glycoside are attacked byemulsin are regarded as β-glycosides.4- Maltase and invertase are α-glycosidases, capable of hydrolyzing α-glycosides only.1- Water mixed with different proportions of methanol or ethanol (most suitable extracting solvent).2- Non-polar organic solvents are generally used for de-fating process.3- Glycosides are not precipitate from aqueous solutions by lead acetate.1- Destruction of hydrolysing enzymes.a. Drying for 15-30 min. at 100 C˚.b. Place plant in boiling water or alcohol 10-20 min.c. Boiling with acetone.d. Cold acid pH treatment.e. Extract at very low temperature.2- De-fating or purification of the plant material (in case of seeds).3- Extraction of the glycosidal constituents by alcohol, water or dilute alcohols. Some times ethersaturated with water for dry material.4- Concentrate the alcoholic extract (to get rid of the organic solvent). Add water (or hot water)→filter any precipitate.5- Purify aqueous extract:a- Extract non glycosidal impurities by org solvent.b- Water soluble impurities precipitate by lead acetate.6- Precipitate excess lead salts.7- Isolation of the glycosides from the purified aqueous solution, by crystallization.
8They do not themselves reduce Fehling’s. but reducing sugars upon hydrolysis.To test for the presence of glycosidesEstimate reducing sugars before and after hydrolysis. (by acids or enzymes)1- Steroidal or cardiac glycosides:Give positive Liebermann’s test (steroidal structure).2- Anthraquinone glycosides and/or aglycone:Give positive Borntrager’s test, characteristic reddish coloration with alkalies.3- Flavonoidal glycosides and/or aglycones:Characteristic color with, NH4OH, AlCl3, FeCl3.4- Cyanogenetic glycosides give upon hydrolysis hydrocyanic acid can be easily tested by changeNa bikrate paper (yellow) to red color.5- Sulphur containing glycosides give black precipitate of silver sulphate upon treatment withAgNO3 solution.1- Keller Killiani’s test for 2-deoxy sugers:Specificity of action of the hydrolyzing enzymes is often applied for the identification of the sugarmoieties of glycosides or even the glycoside as alcohol.1- Scillarin A [acid hydrolysis] →→→ Scillaridine A + Scillabiose Scillabiose [Scillabiase] →→→ Rhamnose + glucose.
9 CHO2- Prunasin [Prunase] →→→ glucose + HCN + H OC 6 H 11 O 5 C CN3- Amygdalin [amygdalase] → Prunasin + glucose4- Myrosin enzyme is specific for thio D- glucosides e.g., Sinigrin and sinalbin.Determination of the glycosidic linkages:1- By the use of α and β glycosidases.2- By acid hydrolysis of glycosides, immediate optical activity measurement of the resultingsolution.Color reactions based on the sugar moiety [2-deoxy sugars]:1- Keller Killiani:glacialacetic acid containing + FeCl3 + H2SO4 → brown ring free from red (acetic acid a quire blue).2- Xanthydrol:xanthydrol in glacial acetic containing 1% HCl + glycoside [heat]→ red color.N.B. Stability indicating after extraction. U.S.P.Medicinal importance of glycosides:1- Cardiac drugs: cardiotonic glycosides e.g., digitalis glycosides, strophanthus, squill.2- Laxatives e.g., anthraquinone glycosides of senna, aloes, rhubarb, cascara, frangula.3- Counter irritants e.g., thioglycosides and their hydrolytic products ‘allylisothiocyanate’4- Analgesics e.g., methylsalicylate ‘a hydrolytic product of gaultherin.5- Anti rheumatic e.g., salicin.
106- Some glycosides are claimed to reduce the capillary fragility e.g., flavonoidal glycosides, rutin, hisperidin.7- Anti-inflamatory: e.g., the glycoside glycyrrhizin has a demulcent, expectorant and antispasmodic action.8- More recently as an anticancer agent e.g., amygdalin known in the U.S. as Laetrile.1-The genins of all cardiac glycosides are steroidal in nature, that act as cardiotonic agents.2-They are characterized by their highly specific action cardiac muscle, increasing tone, excitabilityand contractility of this muscle, thus allowing the weakened heart to function more efficiently. Lactone ring 12 CH3 17 11 13 1 16 R 9 14 2 15 10 8 OH 3 7 Sugar O 5 4 6All cardio active glycosides are characterized by the following structural features:1- The presence of β-OH at position C-3, which is always involved in a glycosidic linkage to a mono,di, tri, OR tetra saccharide.2- The presence of another β-OH group at C-14.3- The presence of unsaturated 5 or 6- membered lactone ring at position C-17, also in the βconfiguration.4- The A/B ring junction is usually (cis), while the B/C ring junction is always (trans) and the C/Dring junction is in all cases (cis).5- Additional OH groups may be present at C-5, C-11 and C-16.
111- Cardiac glycosides that α-β unsaturated 5-membered lactose ring in position C-17 are known ascardenolides. These are represented by the digitalis and straphanthus group.2- Digitalis glycosides contain angular methyl group at C-10, while strophanthus glycoside arecharacterized by presence of either an aldehydic (CHO) or primary alcoholic (C`H2OH) group at C-10. O O OH 12 CH3 17 11 13 1 16 R 9 14 2 15 10 8 OH 3 7 Sugar O 5 4 6 CardenolidesDigitalis glycosides R=CH3Strophanthus glycosides R=CHO OR CH2OH3- Cardiac agents that have doubly unsaturated 6-membered lactone ring in position C-17 arereferred to as Bufadienolides.4- This group includes the squill glycosides and the toad venom, Bufotoxin. O O OH 12 17 11 13 1 16 9 14 2 15 10 8 R1 3 R2 7 Sugar O 5 4 6 Bufadienolides
12Squill glycosides R1=OH, R2=HBufotoxin R1 & R2 = ester group5- The glycone portion at position C-3 of cardiac glycosides may contain four monosaccharidemolecules linked in series. Thus, from a single genin one may have a monoside, a bioside, a trioside ora tetroside.6- With the exception of D-glucose and L-rhamnose, all the other sugars that are found in cardiacglycosides are uncommon deoxy-sugars e.g., Digitoxose, Cymarose, Thevetose. CHO CHO CHO C H2 C H2 HC OH C OH C OCH3 CH3 O C H C OH C OH H C OH C OH C OH H C OH CH3 CH3 CH3Digitoxose Cyamarose ThevetoseIsolation difficulties:1. Major difficulty in the isolation of 1ry glycosides from the crude drug.. why? because 1ry glycosidesare converted into secondary glycosides by hydrolysable enzymes.2. Other difficulty is the existence of several closely related glycosides in the same drug, which areextremely difficult to separate and purify.Origin: D. purpurea, D. lanata, D. lutea and D. thapsiThe structures of the common aglycones of the digitalis group are indicated below:
13 O O R1 17 11 12 13 1 16 R2 9 14 2 15 10 8 OH 3 7 H O 5 4 6Compounds R1 R2Digitoxigenin H HGitoxigenin H OHDigoxigenin OH H DX = Digitoxose, DX (AC)=Acetyldigitoxose,G = Glucose.1- Glycosides derived from Digitoxigenin:a- Lanatoside A = Digitoxigenin---DX---DX----DX(AC)---G.b- Acetyl-digitoxin = Digitoxigenin---DX---DX----DX---(AC).c- Digitoxin = Digitoxigenin------DX---DX----DX.d- Purpurea gly A = Digitoxigenin---DX---DX----DX---G2- Glycosides derived from Gitoxigenin:a- Lanatoside B = Gitoxigenin---DX---DX----DX(AC)---G.b- Acetyl-gitoxin = Gitoxigenin---DX---DX----DX---(AC).c- Gitoxin = Gitoxigenin------DX---DX----DX.d- Purpurea gly B = Gitoxigenin---DX---DX----DX---G
143- Glycosides derived from Digoxigenin:a- Lanatoside C = Digoxigenin---DX---DX----DX(AC)---G.b- Acetyl-digoxin = Digoxigenin---DX---DX----DX---(AC).c- Digoxin = Digoxigenin------DX---DX----DX.d- Deslanoside = Digoxigenin---DX---DX----DX---G1- The 1ry glycosides Lanatoside A, Lanatoside B, Lanatoside C are acted by specific enzymewhich split the terminal glucose, give the 2ry glycosides acetyldigitoxin, acetylgitoxin andacetyldigoxin respectively.2- The deacetyl-lanatosides A, B and C can be obtained by the alkaline hydrolysis of thecorresponding lanatosides.3- Digitoxin, gitoxin and digoxin are obtained by the action of alkali on their acetyl-derivatives. Lanatoside A Alkaline Specificpurpurea gly. A Acetyldigitoxin hydrolysis enzyme Specific Alkaline Digitoxin enzyme hydrolysis Acid hydrolysis Digitoxigenin + 3 digitoxose1- The glycoside K-strophanthoside (a trioside), K-strophanthin B (bioside) and cymarin (amonoside) were isolated from different strophanthus species.2- The 1ry glycoside K-strophanthoside gives by hydrolysis one molecule of glucose and the 2ryglycoside K-strophanthoside B or K- strophanthin B.
153- The later gives by hydrolysis one molecule of glucose and the tertiary glycoside cymarin, whichon turn hydrolyze into the genin K-strophanthidin and the deoxysugar cymarose. O O 17 11 12 K- strophanthidin 13 1 16 CHO 9 14 Cymarin 2 15 10 8 OH 3 5 K- strophanthin B 7 O 4 OH 6 K- strophanthoside Cymarose B-glucose a-glucoseThe seeds of Strophanthus gratus contains another glycoside named Ouabain or (G-strophanthin),which yield on hydrolysis rhamnose and the aglycone ouabagenin.Ouabagenin differs from K-strophanthidin in having 2 additional (OH) groups at C-1 and C-11 andhaving a 1ry alcoholic group at C-10 instead of the aldehydic group. O O OH OH 17 12 OH 11 13 16 CH2 9 14 2 1 15 10 8 OH 3 Rhamnose 7 O 5 4 6 OH Ouabain (G-strophanthin)
16This group of cardioactive agents includes the squill glycosides (the scillarins) and the Toad poison(Bufotoxin).The genins of squill glycosides differ from those of the cardenolides in two important aspects:1- They have six membered doubly unsaturated lactone ring in position C-17.2- They have at least one double bond in the steroid nucleus. O O OH Glucose-Glucose-Rhamnose O Scillaridin A Proscillaridin A Scillarin A Glucoscillarin A The Bufadienolides of SquillName of glycosides StructureGlucoscillarin Scillaridin A ---RH—G---GScillarin A Scillaridin A ---RH—GProscillaridin A Scillaridin A ---RH
17* The different cardiac glycosides show different solubilities in aqueous and organic solvents. Theyare usually soluble in water or aqueous alcohol and insoluble in the fat solvents with exception ofchloroform and ethylacetate.* The higher number of sugar units in the molecule, the greater solubility in water but lower soluble inchloroform.* Alcohols are good solvents for both the glycosides and the aglycones. Therefore, they are consideredas the solvents of choice for the extraction of all CG from drugs.* pet.ether and ether are used for defatting process of drug, they do not dissolve CG.1- Acid hydrolysis cleavage of the glycosides into aglycones and sugar residues.2- Specific enzyme usually coexist with CG in plants, which may split the primary G into G with lesssugar units. Thus, CG deteriorate during drying and storage unless special precautions are taken.3- So it is required by many pharmacopoeias that CG containing drugs must contain not more thanspecified moisture content and that these drugs should be stored in sealed containers overdehydrating agents.4- It is recommended to heat stabilize these CG, by destroying the enzymes at higher temperatures. Athigher temperature, the tertiary OH gp at C-14 may split off as water, leading to formation of aninactive anhydro-form of CG. O O O O 12 CH3 12 CH3 17 17 11 13 11 13 1 16 -H2O 16 R 9 14 1 R 9 14 2 15 2 15 10 8 OH 10 8 3 3 7 7Sugar O 5 6 Sugar O 5 4 6 45- The gitoxin has in addition to tertiary OH at C-14 another secondary OH at C-16. Both OH gpssplit as water by the action of H2SO4 with the formation of two additional double bonds. These with
18the double bond of the lactone ring from a conjugated double bond system that makes the compoundfluorescent in UV light. O O O O 12 CH3 12 CH3 17 17 11 13 11 13 1 R 9 16 OH -2H2 O 1 16 14 R 9 14 2 15 2 15 10 8 OH 10 8 3 3 7 7Sugar O 5 6 Sugar O 5 4 6 4The detection of gitoxin in other digitalis G is based on the above mentioned reaction.1- CGs are steroidal in nature, give +Ve with Liebermann’s and Salkoviski’s test.2- CG that contain deoxy-sugars are distinguished by Keller Kiliani’s test, e.g., digitoxose andcymarose.3- Cardenolides are distinguished from the scillarins by a group of color reagents, that are allalkaline solutions of aromatic nitro compounds, namely,Kedde’s reagent, 3,5 dinitrobenzoic,Raymond’s reagent, metadinitrobenzene,Baljet’s reagent, picric acid,Legal’s test, alkaline solution of sodium nitroprusside.4- All these nitrocompounds react with the active methylene of the five membered lactone ring (inalkaline medium) to give characteristic colors.1- Cardiotonics, CHF, rheumatic heart disease, atherosclerosis, HTN.2- Diuretics (capillary of the kidneys are dialated).
191- The glycone part displays a great influence on the solubility and the rate of absorption anddistribution of the glycosides to the site of action.2- Small change in the molecules such as a change of the location of the OH gp, modify the cardiacactivity or even eliminate it completely.3- The saturation and/or cleavage of the lactone ring, destroys the cardiac activity.Therefore, the closely related CG, differ greatly in the rate of absorption, duration of action andtheir cumulative effect.1- digitalis leaf (digitalis tablets)2- digitoxin tablets 200μg/tablet3- digoxin injection contain 0.0025% digoxin4- digoxin tablets contain 250μg/tablet5- gitalin, lanatoside C, deslanoside, strophanthus, strophanthin, ouabain and squill.
20 Anthraquinone Anthrone Anthranol O O OH 8 1 8 17 9 2 7 9 2 4H6 10 3 6 10 3 5 4 5 H H 4 O H O 2H 8 1 7 9 2 6 10 3 5 H 4 OH Oxanthrone1- O-glycosides where the aglycone moiety is 1,8 dihydroxyanthraquinone derivatives, e.g.,Gl O O OH O 1 Gl O OH Gl O O OH 1 1 8 9 2 8 9 2 8 9 2 10 CH2 OH 10 10 5 4 COOH CH3 5 4 5 4 O O O Aloe-emodin-8-glycoside Rhein-8-glycoside Chrysophanol-8-glycoside2- O-glycoside where the aglycone moiety partially reduced 1,8 dihydroxy anthraquinone, e.g.,Oxanthrone-type. Gl OH OH H O 7 8 9 1 2 6 10 3 5 4 O Emodin-oxanthrone-9-glucoside3- C-glycoside where the aglycone structure (anthrone der.) O OH OH 7 8 9 1 2 6 10 4 3 5 CH2 OH H C6 H11 O5
21 Barbaloin4- O-glycosides where the aglycone moiety is di-anthrone der. (i.e., dimmer) e.g., Sennosides wherethere is C-C bridge between the anthranol units. Sennoside A&B Gl O O OH 7 8 9 1 2 6 10 4 3 COOH 5 H H COOH Gl O OH OThe most widely used drugs that contain anthracene compounds are:Consists of the dried leaflet of Alexandrian or Khartoum senna, Cassia senna (C.acutifolia),Tinnevelly senna (C.angustifolia).Constituents:Dimeric anthracene glycosides derived from two anthrones moieties which may be: O OH OH 1 O OH OH 8 9 1 2 8 9 2 10 CH2 OH 10 5 4 COOH 5 4 Aloe-emodin anthrone Rhein anthrone1- Similar anthrone moiety (Homo-dianthrones) i.e., 2 rhein anthrone moieties condensate throughtwo C-10 atomes. Thus it can be exist in two optical forms, Sennoside A (L- form) & Sennoside B(meso form).
22 Gl O O OH 7 8 9 1 2 6 10 4 3 COOH 5 H H COOH Gl O OH O Sennosides A &B2- Or different (Hetero-dianthrones) i.e., one rhein-anthrone & one emodin anthrone, Sennoside C(L- form) and Sennoside D (meso form). Gl O O OH 7 8 9 1 2 6 10 4 3 CH2 OH 5 H H COOH Gl O OH O Sennoside C&DThe dried bark of Rhamnus purshiana Family Rhamnaceae. B. P. specified that the collection mustbe made at least one year before the bark is used (fresh bark contains an emetic principle).Constituents:A- Four primary glycosides:1- cascarosides A&B (glycosides of barbaloin)2- cascarosides C&D (glycosides of chrysaloin)
23 OH O OH O OH Gl O CH2 OH CH2 OH H Gl H Gl Barbaloin Cascaroside A& B O OH Gl O O OH OH CH3 CH3 H Gl H Gl Chrysaloin Cascaroside C & D B-Two aloins(secondary glycosides):Barbaloin derived from (C-10-C-glycoside) of aloe-emodin anthrone and chrysaloin derived from(C-10-C-glycoside) of chrysophanol anthrone.C- A number of O- glycosides:e.g., derived from emodin, emodine oxanthrone, aloe emodin and chrysophanol. OH O OH OH O OH CH2 OH CH3 O O Aloe emodin ChrysophanolE- Free anthraquinones:Aloe emodin, chysophanol and emodin.1- Frangulin (frangula emodin rhamnoside).2- Glucofrangulin (frangula emodin glucorhamnoside).
24 OH O OH RO CH3 O Frangulin R= Rhamnose Glucofrangulin R= Rhamnose-glucose3- hydrolysis of glucofrangulin yields frangulin and glucose.4- Hydrolysis of frangulin gives frangula emodin and rhamnose.1- Consist of glycoside of rhein, rhein anthrone, chrysophanol and aloe emodin.2- Dianthrones of heteroanthrone types are palmidin A, B, C, Rheidins, sennosides A&B and theiroxalate esters (sennosides E&F).3- The presence of tannins in rhubarb makes the drug constipating. So in small doses, rhubarb exertsno purgative action but acts only as intestinal astringent, but large doses cause purgation.Cascara is a purgative, mainly in the form of liquid extract, elixir or as tablets prepared from a dryextract.The laxative action of the crude drugs is always higher than from their content of anthraceneder. The different anthracene der. contained by the crude drug are said to exert a synergisticaction.Thus, the naturally occurring anthracene glycosides were found superior to the synthesis ofnumerous hydroxyl anthracene der.Some of these synthetic compounds act too drastically and also caused kidney damage.The only compound which is used to some extent in current medicine is danthrone. It is alsoused as a standared in colorimetric assays of anthraquinone glycosides.
25 OH O OH O DanthroneNote:1- The 1ry glycosides are more active than the aloins while the free anthraquinon have littlepurgative activity.2- C-C glycosides, aloins are very resistance to hydrolysis and are not easily hydrolysed (like otheranthrones and anthranols) to corresponding anthraquinones.3- Aloin type glycosides are present in aloes and other anthracene bearing drugs of the familyliliaceae.1- Glycosilation:The purgative action of anthracene bearing drugs is owed to their anthracene glycosidal content ratherthan their content of free anthracene aglycones (i.e., glycosylation is the main requirement for activity,as the sugar moiety serve to transport the aglycone to the site of action in the large intestine).2- Hydroxylation:Hydroxylation of C-1, C-8 is essential for activity. Increase hydroxylation leading to increasesolubility.3- Oxidation level:The degree of oxidation at positions C-9 & C-10 plays an important role in the pharmacologicalactivity. Higher oxidation level at C-9 & C-10 caused lowering of activity. i.e., anthrones andanthranols are more potent than their corresponding oxanthrones, which in turn more active than theircorresponding anthraquinones. Complete reduction of C-10 &C-9 lead to complete loss of activity.4- The nature of substances at C-3:Derivative with CH2OH (as in aloe emodin) are more active than those with CH3 substitution. Thelatter more active than derivative with COOH substitution at C-3.
26Anthraquinone glycosides containing adimer more active than a monomer.5- Effect of storage on the active of anthracene glycosides:a- Prolonged storage of anthracene bearing drugs may bring oxidation of anthranols and anthrones togive the less active anthraquinones. Thus, the activity of drugs decreases by time. However,anthraquinone glycosides do not cause any griping action (like anthranol and anthone), thus noantispasmodic such as belladonna is prescribed with them.b- Drugs as senna, Aloe and cascara preparations retain their activity for a long time.c- Cascara and frangula must be aged for one year before it is used for medicinal preparation.WHY?Stability is achieved as follows:1- In senna, there is dimeric glycoside in which a C-C bridge between two anthrone units is formed(the C-10 position of one anthrone is involved in a C-C-covalent bonding with C-10 of the otheranthrone). Thus, the C-10 position can not be easily oxidized and the anthrone structure is stabilized.2- In the aloe, the aloins (barbaloin & chrysaloin) contain C-C glycosidic linkage (anhydroglycosides)stabilise the anthrone structure.4- In cascara, cascarosides have an additional O-glycosidic linkage (beside the C-10-C glycosidiclinkage. The solubility of cascarosides is increased and thus, produce higher pharmacological activity.The glycosides are extracted and hydrolyzed by boiling the drug with acids.The aglycones are extracted from the acidic solution with ether or benzene. Upon shaking the ether orbenzene layer with aqueous alkali or ammonia solution, the aqueous layer assumes a deep red color,because of the formation of anthraquinone salts.Borntrager’s reaction can distinguish anthraquinones from anthrones and anthranols which do notgive the test unless they are converted to anthraquinone by oxidation with mild oxidants such ashydrogen peroxide or ferric chloride.Official anthraquinone drugs in B.P and U.S.P.:1- Senna leaf & senna fruit (pod).2- Aloes.3- Cascara tablets, elixir, dry exract, liquid extract.
274- Rhubarb powdered, tincture.5- Danthrone6- Frangula bark- Flavonoidal compounds are considered as the largest group of naturally occurring phenols.- Flavonoidals constitute the majority of the yellow colored plant pigments.- Many flavonoidal compounds present as a glycosidic or as a free forms.- All derived from the same parent nucleus, 2-phenyl-benzopyran (flavan), thus they have a basic C-15 skeleton.Flavonoidal compounds are classified according to the oxidation level of central pyran ring they areclassified into flavones, isoflavones, flavonols, flavanones, (true flavanoids) anthocyanidins,chalcones and aurones.True flavones, are 2-phenyl chromones (2-phenyl benzopyrone), while isoflavones are 3-phenylchromones der.Flavonols are 3-hydroxyflavones, while flavanones are 2,3-dihydro der. of flavones (2,3-doublebond is lacking).(2-phenylbenzopyran) (2-phenylbenzopyrone)
28 1 2 3 8 9 O 1 O 7 2 4 6 4 3 10 6 5 5 Flavan O Flavone O O OH O O Flavonol Isoflavone O H H O FlavanoneAnthocyanidines, chalcones and aurones are lack the typical flavone structure. Anthocyanidins and itsglycosides (anthecyanins) are ionic oxonium salts. This is responsible for the permanent blue, purple,violet, mauve, and red color of flower, fruits and leaves of higher plants.Anthocyanidins and anthecyanins are soluble in polar solvents.Cyanidin chloride is an example of anthocyanidines . - R Cl OH + 2 3 2 3 8 8 + 9 O 1 OH 9 O 17 4 OH - 7 4 OH X6 3 6 3 10 6 5 6 5 R 10 OH 5 5 Anthocyanidins OH Cyanidin chlorideChalcones, have no central pyrone ring, so they are not true flavonoidal compounds. The parentcompound chalcone, is chemically phenyl-styryl ketone, or benzylidene acetophenone.Aurones are oxidized forms that are obtained by enzymatic oxidation. Instead of the central pyronering of the normal flavonoidal structure, aurones have five membered ring.
29 O CH O O Chalcon AuroneFlavonoids dissolve in alkalis give intense yellow color solution, on the addition of acid becomecolorless.Flavonoids exhibit strong fluorescence under UV light.Flavonoidal glycosides are soluble in water and alcohol. Ethylacetate is the solvent of choice for theextraction of flavonoids from aqueous solution.Flavonoids compounds may be characterized through the investigation of their UV Spectra, thatusually show two main bands,1- Band at higher wavelength (band I) which is attributed to the cinnamoyl fraction of theflavonoidal structure Why?.2- Band at lower wavelength (band II) which is due to the benzoyl fraction of the flavonoidalstructure.
30 Benzoyl O B A R Cinnamoyl O A II I Band Band 200 Wave length 400 Hypsochromic shift Bathochromic shiftBand I >> 300 nmIf R= H R=OH R=O-substitutionFlavones flavonols 3-sub flavonolBand I: 304-350 nm Band I: 352-385 Band I: 328-357Band II << 300nm(250-280 nm)Note:More OH in ring A: Bathochromic shift in band II.More OH in ring B: Bathochromic shift in band I.Shift reagents:Back to lab.1- Diosmin: flavone glycosideOccurance: buchu leaves, Barosma crenulata F. Rutaceae.Uses: diuretic and diaphoretic action of the leaves is owed in part to diosmin, and in part todiosphenol, the main constituent of the volatile oil of the leaf.
31 OH Rha-Gl O O B OCH3 A OH O DiosminUpon hydrolysis, diosmin yields rhamnose, glucose and diosmetin.2- Rutin and quercetrin: are examples of flavonol glycosidesa- Rutin occurs in the leaves of buckwheat. It is the 3-rhamnoglucoside (called rutinose) of the geninquercitin.It gives on hydrolysis the aglycone (quercitin) beside one molecule of glucose, and one molecule ofrhamnose.Rutin is used to1- Decrease capillary fragility.2- It is a biflavonoids that plays a true vitamin function.b- Quercitrin is quercitin 3-O-rhamnoside.It occurs in the bark of Quercus tinctoria.Quercitrin yield upon acid hydrolysis rhamnose and quercetin.The aglycone quercetin occurs in bearberry leaves (Uva Ursi) and has a diuretic action of the leaves. OH HO O B OH A OR OH O Quercetin: R=H Quercetrin: R= rhamnosyl Rutin: R=rutinosyl3- Hesperidin: it is an example of flavanones. It is the main flavonoidal glycoside of citrus fruits.
32 OH R O O B OCH3 A OH O Hesperitin R:H Hesperidin R:rutinosylUpon hydrolysis by acid, hesperidin gives rhamnose, glucose and hesperitin.Uses:1- Hesperidin appears to be identical to vitamin P (citrin).2- It is necessary for absorption and retention of vit C that lead to decrease capillary fragility.3- Decrease CVD and HTN.Uses of flavonoids:1- Increase capillary resistance and decrease vitamins C & P deficiency.2- They are recommended in the treatment of thrombopenia (blood coagulation).3- They are reported of value in the treatment of influenza, when given with ascorbic acid.Isoflavone:1- Genistein show significant oestrogenic activity. HO O OH O OH2- Rotenoids employed as insecticide. O O O O
33 Flavono-lignansCoupling of a flavonoid moiety with hemi-lignan molecule by oxidative coupling. OH O B OH OR A + OH OH O Flavonoid moiety Hemi-lignan moiety OH O B O A OH O OH O OCH3 OH FlavonolignanThe leaves and fruits of Silybum marianum family Compositae contain silymarin (silybin). OH O B O A OH OH O OH O OCH3 Silybin OH1- Silymarin is a very effective lipotropic and hepato protective therapy.2- It is a free radical scavenger.3- Supportive treatment of acute and chronic alcoholic poisoning and toxin induce hepatitis.
344- It is used for treatment of liver cirrhosis caused by plant toxins (mushroom, amanita), silymarin isapplied as intravenous injection.5- Silymarin is available in the market in the form of tablets, effervescent granules. Trade namelegalon, silyhexal, silirex…etc. Synthetic flavonoidsFlavoxate: O O N O B A CH3 O FlavoxateUses:To remove pain (anti-spasmodic) and anti-inflammatory of the genitor urinary tract.Flavoxate tablets are available under several names: Urispas, Uronid, Spasurit, Genurin).* Saponins are a group of amorphous colloidal glycodides which is wiedly distributed in the higherplants.* Have ability to form lasting foam when shaking in aqueous solution.* They are excellent emulsifying agents (modify surface tension).* Formerly used as detergents to replace soap (e.g., quillaia).* Saponins are colorless and optical active. They form colloidal solution with water and are soluble inalcohol and dilute alcohols.* Saponins have haemolytic properties, they precipitate the cholesterol and lethisins that exist in thememberanes of the red blood cells and thus haemoglobin is liberated. So, saponins are extremely toxicwhen injected into the blood stream. However, they are not harmful when taken orally.* Saponins are difficult to purify. However, they precipitated from solutions containing them by theaddition of a solution of the sterol, filtering off the insoluble sterol-saponin compound and boiling itwith toluene which resolves the compound again into sterol (which is soluble in toluene) and saponin(which is insoluble in toluene).Chemically:
35Saponins are classified according to the genin part into:1- Steroidal type C25.2- Triterpinoidal type C30.Both types of saponins have the glycosidic linkage at position 3. O O COOH R2 HO HO R1 Diosgenin Quillaic acid: R1=CHO, R=OH Olianolic acid R1=CH3, R2=HMedicinal importance of saponins:1- The steroidal saponins are structurally related to modern synthetic compounds that have atherapeutic significance, such as adrenocortecoids and the sex hormones. So, they are a suitableprecursors in the partial synthesis of these hormones, e.g., Diosgenin (sapogenins) isolated from therhizome of Dioscoria species. CH3 OH CO O OH O O O Testosterone Progesterone O CH2 OH CO OH O O HO O Cortisone Diosgenin2- Saponins increase the rate of absorption of many pharmacological active substances (e.g., cardiacglycosides).
363- Many saponin-containing drugs are used as expectorants (e.g., Ipeca, Senaga and liquorice) astheir contents of saponins stimulate bronchial secretion and also activate the ciliary epithelium ofthe bronchi.a-The triterpenoidal saponin glycoside, glycyrrhizin, is the main sweet principle of liquorice. It iscalcium and potassium salts of glycyrrhizic acid, which in tern is the diglucuronic acid glycoside ofglycyrrhitinic acid. COOH O Glucuronic-glucuronic O B-Glycyrrhitinic Glycyrrhizic acid Glycyrrhizin =Ca, Kb- Beside being a valuable flavouring and sweetening agent, liquorice has demulcent, expectorant andantispasmodic action. All these activities attributed to the saponin, glycyrrhizin.c- Recently, glycyrrhizin was shown to be effectively in gastric ulcer treatment and have a cortisonelike action in rheumatic arthritis and other inflammatory diseases.Saponins drugs officially in the B.P and U.S.P:1- Quillaia bark: used as emulsifier.2- Liquorice root: used as flavouring agent and expectorant.1- Tannins are widely distributed phenolic plant constituents.It is characterized by being able to combine with proteins of animal hides thus preventing theirputrefaction and converting them into leather (true tannins).
372- Tannins are detected qualitatively by Goldbeater’s skin test (a tanning test), and can bequantitatively estimated by absorption on standard hide powder. Only high molecular weighttannins that are capable of tanning hide.It is more acceptable to define true tannins as those high molecular weight phenolic plant constituentsthat can be detected by Glodbeater’s skin tanning test.3- True tannin solutions have the ability of precipitating soluble proteins (gelatine), heavy metals,alkaloids and glycosides.4- This will exclude simple molecular weight compounds such as gallic acid, catechin, flavan-3,4-diol and chlorogenic acid, that usually coexist with true tannins. These simpler tannins likecompounds are referred to as pseudotannins. HO HO HO OH HO OH COOH COOC6 H11 O5 Gallic acid Glucogallin OH HO CH=CH-COO OH HO OH OH HO O Chlorogenic acid OH OH Flavan-3,4-diolHydrolysable tannins Condensed tannins1- Hydrolysable tannins:
38a- These can be hydrolyzed by acids or enzymes to give phenolic acids (gallic or ellagic) andglucose, so called phenolic acid glycosides.b- Tannins of gallic acid are called gallitannins and those of ellagic acid is called ellagitannins.c- Dry distillation of hydrolysable tannins gives pyrogallol. This class is named pyrogallol tannins.d- Gallitannins and ellagitannins react with ferric salts to give bluish color precipitate.2- Condensed tannins:a- These are more resistant to hydrolysis upon prolonged heating with acids.b- They undergo decomposition (not hydrolysis) to give a red soluble compound (phlobaphane).c- Condensed tannins are derived from catechin and flavan, 3,4-diol.d- Dry distillation of condensed tannins gives catechol. This class is named catechol tannins.e- Being phenolic, it reacts with ferric salts to give greenish color precipitate.1- Salicin:Salicin is classified as:1- Alcoholic glycoside, as it contains free primary alcoholic group.2- A phenolic glycoside, as its aglycone is phenolic in nature. CH2 OH Gl O Salicin
39 CH2 OH Gl O Acid Enzyme CH2 OH CH2 OH O + Glucose HO + Glucose Saligenin CH2 OH Saliretin1- Salicin is obtained from different species of Salix, the principle commercial source is Salixfragilis.2- Salicin is used for many years as a remedy in the treatment of fever and rheumatism.3- It is now used as an analgesic-antipyretic in case of periodic fever. It is better tolerated in thestomach than sodium salicylate, asprin and other antipyretics and anti-inflammatory agents, whichhave largely displaced in medical practice.4- Salicin is hydrolyzed by the enzyme emulsin into saligenin (Salicyl alcohol) and glucose.5- Acid hydrolysis of salicin gives glucose and a phenolic ether called saliretin which is acondensation product of two molecules of saligenin.6- Oxidation of saligenin gives salicylic acid and this accounts for the medicinal value ofsalicin.1- Arbutin is a phenolic glycoside that occurs in bearberry leaves Arectostaphyllos uva ursi.2- When hydrolysed with acids or with emulsin it yields glucose and hydroquinone.3- It is used as diuretic and also has bactericidal action. This activity is due to the hydroquinone givenby hydrolysis.
403- Uva ursi leaf contains also methylarbutin (the methyl ether of arbutin), that alsocontributes to the diuretic and urinary antiseptic action of the leave. OH OCH3 O-Gl O-Gl Arbutin Methylarbutin1- Glucovanillin is a glycosidal constituent of green vanilla pods.2- The fruits of the plant (pods) are collected and carefully cured. To permit enzymaticaction on the glycoside with the liberation of vanillin (the aglycone) which is the principal flavouringconstituent of the pods.3- Vanillin is widely used as a flavouring agent. It may be obtained from vanilla pod orprepared from the glycoside coniferin, lignin or from the phenolic volatile oil constituents eugenol.
41 CHO CHO OCH3 OCH3 O-Gl OH Glucovanillin Vanillin1- From Coniferin and lignin CH=CH-CH OH 2 CH=CH-CH OH 2 CHO Hydrolysis Oxidation OCH3 OCH3 OCH3 O-Gl OH OH Coniferin Coniferyl alcohol Vanillin2- From Eugenol CH2 -CH=CH2 CH=CH-CH3 CHO KOH Oxidation OCH3 OCH3 OCH3 OH OH OH Eugenol isoeugenol VanillinThe bulk of vanillin which is produced commercially is prepared from lignin, which gives uponhydrolysis coniferyl alcohol. Hydrolysis Lignin coniferyl alcoholLignin is obtained in extremely large amounts as a by product of timber industry.
421- These are glycosides that are yield hydrocyanic acid as one of their hydrolytic products.2- Plant containing these glycosides are toxic.3- The aglycone part is cyanohydrin of a carbonyl compound (condensation product of HCN with analdehyde or keton).4- The majority of cyanogenic glycosides are derived of benzaldehyde cyanohydrin. O OH HCN Sugars C CH Mandilonitrile glycosides H CN Benzaldehyde Mandilonitrile CH3 CH3 CH3 O-Gl OH HCN Sugars C O C C CN CN CH3 CH3 CH3 Acetone Acetone cyanohydrin Linamarin D-Mandelonitrile gentiobioside1- Amygdalin is the most widely distributed cyanophore glycoside.2- It occurs in several Prunus species, and is obtained from bitter almonds (Prunusamygdalus Var. amara Family Rosaceae).3- Amygdalin is considered as gentiobioside of D-mandelonitrile. Gentiobioside is areducing disaccharide consisting of two molecules of β-glucose linked by β-1,6 linkage.
43 CN C O O 6 1 6 1 CH2 CH2 OH H O H 5 O 5 2 3 3 2 4 4 Amygdalin CN C O 1 6 CH2 OH H O 5 3 2 4 Prunasin4- Acid hydrolysis of amygdalin split two molecules of glucose and one molecule ofmandelonitrile. The latter decomposes spontaneously to form benzaldehyde and HCN.5- Different enzymes act upon amygdalin in different ways: Amygdalase Prunase Glocose + Prunasin Glucose + HCN +Benzaldehyde C Prunase Gentiobiose + Benzaldehyde + HCN Gl-Gl-O CN H Emulsin Glucose + Benzaldehyde + HCN Amygdalin or acid
44 The plantmaterial is cutted into small fragments and then a filter paper moistened with sodium picrate is thensuspended in the neck of the flask, the flask is stoppered and incubated in a warm place (40˚C) forabout 30-60 min. By this time, the coexisting enzymes act upon the glycosides with the liberation ofHCN which turns, the sodium picrate paper convert to brick red color. Thioglycosides1- A number of plants of the family Cruciferae yield glycosides containing sulphur.2- Hydrolysis of these, yield volatile genins of thiocyanate structure e.g., mustard oils.3- The best known compounds Sinigrin and Sinalbin, two glycosides occurring in black mustard andwhite mustard seed respectively.4- The glycosides and their specific enzymes are found in different cell in the seeds. They donotinteract until they are brought together by the distruction of the cell walls.5- The general structure of thioglycosides is: S-GL + R C X - N-OSO3
456- The anion is called the glucosinolate ion, R may be aliphatic or aromatic. The cation (X) may be asimple metal ion or a complex organic cation, e.g., sinapine ion of sinalbin. S-GL S-GL CH2 CH-CH2 -C HO CH2 C - N-OSO3 K N-OSO3 - Sinapine+ Sinigrin Sinalbin6- Sinigrin gives upon hydrolysis, glucose, allylisothiocyanate (volatile oil of mustard)and potassium acid sulphate.7- Hydrolysis of the glycoside sinalbin gives a phenolic isothiocyanate (Acrinylisothiocyanate), glucose and the acid sulphate of a quaternary alkaloid, sinapine. + CH3 O CH3 HO CH-CH-COO-CH -CH2 -N 2 CH3 CH3 CH3 O Sinalpine cation8- Black and white mustard seeds are used as rubefacients and counter irritants. Theseeffects are attributed to their contents of thioglycosides.Aglycone 1- coumarin (benzo-α-pyrane).
462-coumarin derivative (hydroxyl and methoxy coumarins).3- Umbelliferone [7-hydroxy coumarin] is the lactone of umbellic acid which occurs bothin the free state and in the form of glycosides in some resins of the Umbelliferae (Asafetida andgalbanum). O O O O HO O O a-pyrone coumarin umbelliferone4- Coumarin and its derivatives give blue or violet fluorescence in aqueous ammonicalsolutions (conjugated double bond system). This is made use of in qualitative testing for coumarin,coumarin derivatives and coumarin glycosides and drugs containing them.5- The oleo gum resin galbanum that contains umbelliferone in a free state isdistinguished from asafoetida that contains only combind umbelliferone, by the addition of ammoniato its aqueous alcoholic extract, when the characteristic blue fluorescence is given. Asafetida respondspositive to the fluorescence test only after acid hydrolysis.