Glycosides are plant-derived compounds formed by the linkage of a sugar molecule to a non-sugar molecule. They have both toxic and beneficial properties. Glycosides contain an active aglycone portion and a sugar portion that helps solubilize the aglycone. Many important drugs are derived from plant glycosides, including cardiac glycosides and laxatives. Alkaloids are another class of nitrogen-containing plant compounds that include many drugs and poisons. They are derived from amino acids and have pronounced physiological effects in humans. Over 3,000 types of alkaloids have been identified in plants.

1. Drugs obtained from Plant
Md. Nafizur Rahman
Dept. of Genetic Engineering & Biotechnology,
Shahjalal University of Science & Technology, Sylhet.

2. Glycosides
Glycosides are substances produced in plants by metabolic processes which are formed by
the ether linkage or an oxygen bridge between a sugar and a non-sugar compound by
replacement of a hydroxyl group in the sugar molecule. They are important in human and
animal nutrition and they have both toxic and beneficial properties. Many plants store
chemicals in the form of inactive glycosides. These can be activated by enzyme hydrolysis,
which causes the sugar part to be broken off.The glycosyl group of a glycoside is replaced
by a hydrogen atom making the aglycone part.
Glycoside is composed of two parts-
a) Sugar part is known as glycone. The glycone can consist of a single sugar group
(monosaccharide) or several sugar groups (oligosaccharide). Glycone part confers on the
molecule solubility properties.
b) Non-sugar part is known as aglycone. It is the active part of glycoside. Sugar helps in the
solubilization of non-sugar, for increasing the bioavailability of the drug. The aglycone part
is responsible for the pharmacological activity.

3. Characteristics of Glycosides
 Glycoside contains sugar but still the physical, chemical and therapeutic activity is based
on aglycon portion. Sugar facilitates the absorption of the glycoside helping it to reach
the site of action.
 Glycoside are crystalline, amorphous substance which are soluble in water, and dilute
alcohol but in soluble in the CHCl3 and ether. The aglycon moiety is insoluble in non-
polar solvent like C6H6.
 Glycosides are easily hydrolyzed by mineral acids, water and enzyme. They show optical
activity normally they are levorotatory.
 Glycoside cannot reduce fehling’s solution until they are hydrolyzed.
 They are believed to facilitates growth and protection of plant.
 Glycosides are water soluble compounds and insoluble in the organic solvents.

4. Classification of Glycosides
1. Based on the chemical nature of non-sugar half:
i) Alcoholic glycosides
An example of an alcoholic glycoside is salicin, which is found in the genus salix. Salicin is
converted in the body into salicylic acid, which is closely related to aspirin and has
analgesic, antipyretic, and anti-inflammatory effects.
ii) Anthraquinone glycosides
These glycosides contain an aglycone group that is a derivative of anthraquinone. They
have a laxative effect. They are mainly found in dicot plants except the Liliaceae family
which are monocots. They are present in senna, rhubarb and Aloe species. Antron and
anthranol are reduced forms of anthraquinone.
iii) Coumarin glycosides
Here, the aglycone is coumarin or a derivative. An example is apterin which is reported to
dilate the coronary arteries as well as block calcium channels. Other coumarin glycosides
are obtained from dried leaves of Psoralea corylifolia.

5. iv) Cyanogenic glycosides
In this case, the aglycone contains a cyanide group. An example of these is amygdalin from
bitter almonds (but not sweet almonds). Cyanogenic glycosides can also be found in the
fruit seeds (and wilting leaves) of many members of the rose family (including cherries,
apples, plums, bitter almonds, peaches, apricots, raspberries, and crabapples).
v) Phenolic glycosides
Here, the aglycone is a simple phenolic structure. An example is arbutin found in the
Common Bearberry Arctostaphylos uva-ursi. It has a urinary antiseptic effect.
vi) Steroidal glycosides or cardiac glycosides
Here the aglycone part is a steroidal nucleus. These glycosides are found in the plant
genera Digitalis, Scilla, and Strophanthus. They are used in the treatment of heart diseases,
e.g., congestive heart failure (historically as now recognized does not improve survivability;
other agents are now preferred) and arrhythmia.

6. 2.Based on the nature of sugar half:
i) Glucoside: sugar portion is glucose
ii) Rhamnoside: sugar portion is rhamnose
iii) Pentoside: sugar portion is pentose
iv) Fructoside: sugar portion is fructose
v) Arabinoside: sugar portion is arabinose
3. Based on therapeutic nature of glycoside:
i) Cardiac glycoside Ex: Digitalis
ii) Laxative glycoside Ex: Senna
iii) Anti-ulcer glycoside Ex: Liquorice
iv) Bitter glycoside Ex: quassia wood
4. Based on linkage between glycon and aglycon portion:

7. a) C-glycoside:-
Glycon-OH + HC –aglycon --> glycone-c-aglycon +H2O
Some of the anthraquinone glycoside like cascaroside in cascara, aloin in aloes shows the
particular linkage. C-glycosides are called aloin type glycoside present in aloes. They do not
hydrolyze by heating with diluted acid or alkalis. Cochical contains c-glycoside in the form
of coloring matter called carminoic acid.
b) O-glycoside
They are common in higher in plants Ex senna, rhubarb
They are hydrolyzed by treatment with acid or alkali into glycon and aglycon portion.
c) S-glycoside
They occurrence of this glycoside is restricted to isothiacyanate glycoside like sinigirin in
black mustard formed by the condensation of sulphohydryl group aglycon to OH group of
glycon.
d) N-glycoside
They most typical representation of this is nucleoside where the amino group reacts with
OH group of ribose or deoxyribose resulting into N-glycoside.

8. Biosynthesis of Glycosides
1. Starting point of the synthesis is a sugar, such as glucose is phosphorylated by ATP.
2. Transfer of a uridylyl group from uridine triphosphate (UTP) to a sugar-1-phosphate
forming UDP-sugar & inorganic pyrophosphate. Enzyme catalyzing this reaction are
referred to as uridylyl transferases.
3. Transfer of the sugar from UDP-sugar to a suitable acceptor (aglycone), mediated by
enzyme glycosyl transferases, thus forming the glycoside.

9. Application of glycosides
Many glycosides are used in production of various types of drugs and therapeutic agents.
The main therapeutic applications are:
 Cardiac drugs (cardiotonic glycosides; e.g., strophanthus, squill)
 Anti-inflammatories (e.g., naringin, naringenin)
 Antipyretics (e.g., salicin), Antivirals (e.g., glycyrrhizin, prunin)
 Antirheumatics, analgesics (e.g., methylsalicylate)
 Demulcent, Expectorant, Antispasmodic action
 Laxatives (e.g., anthraquinone glycosides of senna, aloes)
 Counter-irritants (e.g., thioglycosides)
In cardiac failure glycosides increase the force of myocardial contractions, slow heart rate,
and slow the conduction of electrical impulses. This increased force of contractions
improves the efficiency of the heart without increasing oxygen consumption. As a result,
more blood is pumped from the heart, decreasing congestion. Normal blood circulation is
restored and kidney function is increased.

10. Alkaloids
Alkaloidsany of a class of nitrogenous organic compounds of plant origin that have
pronounced physiological actions on humans. They often have pharmacological effects and
are used as medications, as recreational drugs, or in entheogenic rituals. They include
many drugs (morphine, quinine) and poisons (atropine, strychnine). More than 3,000
different types of alkaloids have been identified in a total of more than 4,000 flowering
plant species.
Alkaloids in plants
About 10-25% of higher plants contain alkaloids. Alkaloids generally abound in the
following parts of plants-
 Leaf-Tobacco (Nicotiana tabacum), tea (Camellia sinensis)
 Seed-caffeine that appears in coffee (Arabian coffea)
 Root-Pokeweed (Phytolacca americana)
 Fruit-Hemlock (Conium maculatum)
 Sometimes alkaloid appear in whole plant such as Yew (Texus bacata)
Furthermore, different tissues of same plant contain different alkaloids.

11. Properties of Alkaloids
 Derived from amino acid and its derivatives
 Toxic, bitter in taste, some contain O2
 Low molecular weight and High melting point
 Most are crystalline solids although few are amorphous
 Usually insoluble or sparingly soluble in water
Classification of Alkaloids
1. Non-heterocyclic Alkaloids:
Non-heterocyclic alkaloids are alkaloids having non-heterocyclic nucleus. They are also
known as Proto alkaloids or Biological alkaloids. They are less commonly found in nature.
Table below shows the chemical structure and example of such compounds-
Types of Alkaloid Structure Example
Phenyl ethylamine
Ephedrine, Narceine
Pseudoephedrine
Capsaicin, Mescalin

12. 2. Heterocyclic Alkaloids:
Heterocyclic alkaloids are alkaloids having heterocyclic nucleus. They are also known as
typical alkaloids. They are more commonly found in nature. Heterocyclic alkaloids are
further subdivided into 14 groups. Table below shows the chemical structure and example
Types of Alkaloid Structure Example
Pyridine Lobeline
Steroidal
Conessine
Veratramine
Purine
Caffeine
Theobromine

13. Biosynthesis of Alkaloids
Amino acids are the biosynthetic precursor of most Alkaloids. They are-
 Tyrosine (e.g. morphine, codeine)
 Tryptophan (e.g. quinin)
 Glumate (e.g. cocaine, nicotine, senecionine)
 Aspartate (e.g. nicotine)
 Xanthine (e.g. caffeine, theobromine)
Biosynthetic Pathway
Some of the general reactions that are of particular importance includes decarboxylation
(removal of carboxyl group or carbon dioxide) and transamination (transfer of an amino
group from one molecule to another without the formation of ammonia) of the amino
acids to yield a corresponding amine or aldehyde. These can react to form a Schiff base
which, in turn can react with carbanion in a Mannich-type condensation.
Synthesis of Schiff bases: Schiff bases can be obtained by reacting amines with ketones or
aldehydes. These reactions are a common method of producing C=N bonds.

14. Fig: Synthesis of Schiff base
In the biosynthesis of alkaloids, such reactions may take place within a molecule, such as
in the synthesis of Piperidine-
Fig: Biosynthesis of Piperidine
Mannich reaction: An integral component of the Mannich reaction, in addition to an
amine and a carbonyl compound, is a carbanion, which plays the role of the nucleophile in
the nucleophilic addition to the ion formed by the reaction of the amine and the carbonyl.

15. Fig: Mannich reaction
The Mannich reaction can proceed both intermolecularly and intramolecularly.
Fig: Overview of alkaloids synthesis pathway

16. Application of Alkaloids
Alkaloids have important role in plant, animal and human life. These have role in plant-
plant interaction, plant-herbivore interaction and plant-microorganism interaction.
Alkaloids either activate or inhibit the central process at cellular and organ level in
animals. They also affect the digestive process and influence the reproductive system of
animals. Many alkaloids, though poisonous, have physiological effect as valuable medicine
against various diseases in human including malaria, diabetics, cancer, cardiac dysfunction
etc. Alkaloids are used as-
 As medicines
 As insect repellents
 As biofertilizers
 As psychoactive drug
 For research and scientific study
As medicine: Medical use of alkaloid-containing plants has a long history since 19th
century. At present, many alkaloids are being used in medicine, usually in the form of
salts, including the following-

17. Alkaloid Action
Caffeine Stimulant
Digoxin Improves heart function
Ephidrine Blood pressure
Morphin Analgesic
Quinine Antimalarial
Theobromine Treatment of asthma
Vincristine Anti-tumor
As insect repellents: Alkaloids can be toxic in varying concentrations. Alkaloid pyrethrin
is used as insect repellent in mosquito coils, mosquito repellents and even in agriculture.
These insecticides are less toxic to humans but affect mosquitoes to leave the vicinity.
As biofertilizers: The use of Lupinex (contains quinolizidine alkaloids, minerals and
carbohydrates) increased yields of cereals, legumes, oil plants, tubers and vegetable crop.
Moreover, later research confirmed that the increase in yield have also been observed in
sunflowers, soybeans and Chinese cabbage.

18. As euphoric & addicting drugs: Many psychotropic substances like marijuna, cannabis,
opium sort if substances are alkaloids. They have been used since ancient period as an
instruments for mental excitement and euphoria. They are considered harmful as per
modern medicine.
For research and scientific study: Due to their specific effects on body, they are used in
research and scientific study. For example, atropine an alkaloid can cause dilation of pupil.
To test if a new substance is having similar effects or opposite effects, it is compared with
atropine. So here atropine is used as standard for comparison in research.
Function of Alkaloids in plants:
 Alkaloids are Poisonous agents which protect plants against insects and herbivores
 Act as regulatory growth factors and considered as reserve substance which is
capable of supplying nitrogen or other elements necessary to the plant’s economy.
 The presence of alkaloids in the plant prevents insects and chordate animals from
eating it. For example, aporphine alkaloid liriodenine produced by the tulip tree
protects it from parasitic mushrooms.
 Alkaloids are also known to regulate plant growth.

19. Volatile Oils
Volatile (unstable) oil is a concentrated hydrophobic liquid containing rapidly evaporating
aroma compounds from plants. Volatile oils are mixture of hydrocarbon terpenes,
sesquiterpenes and polyterpenes and their oxygenated derivatives obtained from various
parts of the plant. Volatile oils evaporate on exposure to air at ordinary’ temperature and
are the odorous constituents. As volatile oil oils are responsible for the essence or odor of
the plant they are also known as essential oils.
Basic Features:
 Mobile liquid at ambient temperature
 Possess very pleasant and characteristic odor which vary considerably from one
specimen to another.
 Colorless liquids with the exception of chamomile oil (violet in color)
 Insoluble in water but soluble in common organic solvent and liposoluble (lipophilic)
 Practically all volatile oils consist of chemical mixers that are often quite complex
 Density is lower than water, with the exception clove or cinnamon
 A large number of volatile oils exhibit optical activity by virtue of the chemical
constitution of the oil(s) or its constitution.

20. Classification of Volatile Oils
The most acceptable classification whereby volatile oils and volatile-oil containing drugs
may be grouped together are as follows, namely:
i. Hydrocarbon volatile oils, E.g. Bitter orange, Turpentine, Juniper, etc.
ii. Alcohol volatile oils, E.g. Mentha, Coriander, Rose, etc.
iii. Aldehyde volatile oils, E.g. Cinnamon Bark, Cassia Bark, Lemon, etc.
iv. Ketone volatile oils, E.g. Caraway, Dill, Spearmint, etc.
v. Phenol volatile oils, E.g. Cinnamon Leaf, Clove, Horsemint, etc.
vi. Ester volatile oils, E.g. Lavender, Rosemary, Sweet Orange, etc.
vii. Phenolic ether volatile oils, E.g. fennel, anise, myristica, etc.
viii. Oxide volatile oils, E.g. eucalyptus, chenopodium, etc.
Volatile oils mainly divided into two broad classes based on their biosynthetic origin:
i. Terpene derivatives
ii. Aromatic derivatives
Many volatile oils consist largely of terpenes.Terpenes are defined as natural products
whose structure may be divided into isoprene units (hemi-terpenes).

21. Biosynthesis of volatile oils
In aromatic plants species, biosynthesis of essential oils occurs through two complex
natural biochemical pathways involving different enzymatic reactions.
They are produced by
i. Cytosolic enzymatic MVA (mevalonic acid) pathway
ii. Plastidic and enzymatic 1-deoxy-D-xylolose-5-phosphate (DOXP), also called the
2-C-methylerythritol 4-phosphate (MEP) pathway
The mevalonate pathway begins with Acetyl-CoA and ends with the production of two
five-carbon building blocks called isopentenyl pyrophosphate (IPP) and dimethylallyl
pyrophosphate (DMAPP), which are used to make isoprenoids. It is best known as the
target of statins, a class of cholesterol lowering drugs.
The non-mevalonate pathway, also known as the 2-C-Methyl-D-erythritol 4-phosphate/
1-deoxy-D-xylulose 5-phosphate (MEP/DOXP) pathway—is an alternative metabolic
pathway for isoprenoid biosynthesis that forms isopentenyl pyrophosphate (IPP) and
dimethylallyl pyrophosphate (DMAPP).

22. Steps for volatile oil production in MVA pathway is:
 Firstly, acetyl CoA is produced from pyruvate which is derived from glyceraldehyde-3-
phosphate and glucose-6-phosphate by a series of reactions in glycolysis pathway.
 Acetyl CoA is again transformed into Acetoacetyl CoA by thiolase enzyme.
 Acetoacetyl-CoA produces HMG-CoA (3-hydroxy-3- methyl-glutaryl-CoA) which is
transformed into Mevalonate.
 Mevalonate is transformed into mevalonate 5-phosphate and resulting metabolite,
mevalonate-3,5-bisphosphate, is decarboxylated to IP, and finally phosphorylated to
yield IPP.
 Isopentenyl diphosphate(IPP) can be transformed intoDMAPP by isomerase enzyme.
DMAPP & IPP are linked in a head to tail fashion resulting in monoterpene which is in
terpenoid group.
Essential oils are final terpenoid products and are formed by a huge group of enzymes
known as terpene synthases (TPS).
Classical MVA pathway is given below….

24. Plants with volatile oils
Plant Essential oil content Therapeutic effects
Basil linolol, cineol, eugenol appetizer, digestive, carminative,
analgesic, antiseptic, healing.
Calendula Gamma terpene,
Sesquiterpenes, Triterpenes
Antiseptic and anti-parasitic
Onion Sulfur compounds Hypoglycemic, expectorant,
hypocholesterolemic.
Clove Eugenol, caryophyllene,
pinene, caryophyllin.
Highly antibacterial, appetizer, anti-
inflammatory.
Turmeric Terpene hydrocarbons and
sesquiterpene ketones.
Choleretic, lipid-lowering,
antispasmodic, bactericidal
Ginger Monoterpenes,
Sesquiterpenes
Carminative, anti-ulcer.

25. Uses of volatile oils
 As insect repellent to prevent the destruction of the flowers and leaves
 Help in the cross fertilization of different species of plants
 Can be used as a flavoring agent
 Used in perfume industries and in cosmetics
 Used in food industries and as preservatives
 As starting material for synthesis of other compounds
 As anti-spasmodic and antiseptic due to high phenols
 Used as a therapeutic agent (oil of eucalyptus)
Therapeutic uses of volatile oils
 As a counter irritant and inhalant
 As carminative, shows anti-spasmodic
 Thymol is used in mouth washes and gargles
 Reduce secretion of lungs in cough and asthma
 Antiseptic, anti-bacterial, anti-fungal and anti-helminthes
 Also used in aroma therapy (e.g. lavander, rosemary)

26. Phenolic compounds
Phenolics are a class of chemical compounds consisting of a hydroxyl group (—OH)
bonded directly to an aromatic hydrocarbon group. They are also called as arenols or
aryl alcohols. These are secondary natural metabolites produced in plants biogenetically
from either the shikimate/phenylpropanoid pathway which directly provide
phenylpropanoids and which fulfill a very broad physiological role in plants
Natural phenolic compoundsfrom medicinal herbs and dietary plants include phenolic
acids, flavonoids, tannins, stilbenes, curcuminoids, coumarins, lignans, quinones etc.
play an important role in various disease prevention and treatment.
Properties of arenols
 Plant phenolics are a chemically heterogenous group
 Some are soluble only in organic solvents
 some are water soluble carboxylic acids and glycosides.
 Another group of phenolics are insoluble polymers

27. Biosynthesis of phenolics
In plants species, biosynthesis of phenolics occurs through two complex natural
biochemical pathways. They are produced by
i. Shikimic acid pathway
ii. Malonic acid pathway
The shikimate pathway (shikimic acid pathway) is a seven step metabolic route for the
biosynthesis of folates and aromatic amino acids (phenylalanine, tyrosine, and
tryptophan).
The first key step in the shikimic acid pathway is the condensation of erythrose-4-
phosphate from the pentose phosphate pathway.
Phenylalanine, tyrosine and tryptophan are the primary metabolites which serve as
precursors for many natural (secondary) products such as flavonoids, phenolic acids,
coumarins, alkaloids, glucosinolates and cyanogenic glycosides.
Phenylalanine ammonia-lyase (PAL) is a key gateway enzyme in the secondary metabolic
pathway leading to the synthesis of phenolic compounds.

28. Fig: Outline of phenolic compound production by shikimic acid pathway.

29. Therapeutic uses of phenols
Various bioactivities of phenolic compounds are responsible for their chemo preventive
properties (e.g., antioxidant, anticarcinogenic, or antimutagenic and anti-inflammatory
effects) and also contribute to their inducing apoptosis by arresting cell cycle, regulating
carcinogen metabolism and ontogenesis expression, inhibiting DNA binding and cell
adhesion, migration, proliferation or differentiation, and blocking signaling pathways.
As antioxidant:
Antioxidant action of phenolic compounds is because of their high tendency to chelate
metals with heavy metals like iron and copper. In human body as well as in plant system,
free radicals are main component which can easily damage cell due to the presence of
free electrons.
Proteins, green vegetables have releases some compounds which can neutralize free
radicals and help to repair the damage occur in cell due to free radicals. Generally,
antioxidants can rapidly lose electron to a free radical and get paired. The pairing of
electron with free radical makes it less harmful.Some phenolic compounds like vitamin-
e, vitamin-c (ascorbic acid) and polyphenols are good antioxidants.

30. Some other uses and applications of phenolic compounds are….
 Phenolic compounds have strong antiseptic and antibacterial properties and act as
nerve stimulants and immunostimulants.
 Phenols sprays are anesthetic and analgesic combinations that work in the painful
and irritating areas.
 Phenols used to relieve pain caused by sore throat.
 Phenolic compounds have potential against oxidative damages diseases, therefore
play a protective role through ingestion of fruits and vegetables.
 These compounds are very much essential for the growth of plant and involve in
reproduction process of plants.
 It is used in insulating materials, paints, rubber, inks, dyes, etc.
 It is used in illuminating gasses, perfumes, soaps and toys.

31. Flavonoids
Flavonoids are group of plant metabolites (polyphenols) thought to provide health
benefits through cell signaling pathways and antioxidant effects. These molecules are
found in a variety of fruits and vegetables in the form of glycosides and sometimes as
acylglycosides, while acylated, methylated and sulfate molecules are less frequent and
in lower concentrations.They are water-soluble and accumulate in cell vacuoles.
Uses of flavonoids
In plants:
 Flavonoids are the most important plant pigments for flower coloration,producing
yellow or red/blue pigmentation in petals designed to attract pollinator animals.
 In higher plants, flavonoids are involved in UV filtration, symbiotic nitrogen fixation
and floral pigmentation.
 Flavonoids secreted by the root of the host plant are sensed by Rhizobia which
triggers the secretion of Nod factors and control root nodule formation.
 Some flavonoids have inhibitory activity against organisms that cause plant
diseases, e.g. Fusarium oxysporum.

32. In humans:
Flavonoids have antioxidant powers that may provide important health benefits. Diets
rich in flavonoids have been associated with reduced risk of a variety of diseases.
Flavonoid-rich foods include cocoa, apples, onions, cranberries, tea and red wine.
 Antioxidant effect: Antioxidants may protect the body’s cells from harmful free
radicals from cigarette smoke and other environmental contaminants.
 Anti-inflammatory effect: Cocoa and chocolate contain a type of flavonoid called
flavonols that may reduce dangerous inflammation in the arteries.
 Anti-cardiovascular disease effect: Flavonols in cocoa may help lower blood
pressure and cholesterol, helping to reduce the risk for heart disease. Flavonoid-
rich foods that may help reduce heart disease risk include apples, onions and black
tea. Cocoa and dark chocolate may also have positive effects on blood clotting,
coronary artery function and insulin sensitivity.
 Anti-Cancer effect: Studies have found that flavonoids inhibit a variety of cancers
in animals. Extracts from flavonoid-rich onions provided strong anti-proliferation
effects against liver and colon cancer cells.

33. Tannins
Tannins (commonly referred to as tannic acid) are water-soluble polyphenols, is an
astringent biomolecule that binds to and precipitates proteins and various other organic
compounds including amino acids and alkaloids. The tannin compounds are widely
distributed in many species of plants, particularly prevalent in a variety of vascular
plants, including fruits (especially grapes), teas, legumes, and grasseswhere they play a
role in protection from predation, and perhaps also as pesticides, and in plant growth
regulation.
Properties of tannins
Tannins are found as shapeless yellowish or light brown masses like powder, flakes or
sponge.Their taste is quite sharp or caustic, providing the distinctive astringency that
humans associate with red wines, teas, and unripe fruits. In their condensed, secondary-
metabolite form, tannins are highly toxic and insoluble compounds, and they bind to
proteins and enzymes. Tannins are usually found in large quantities in the bark of trees
where they act as a barrier for micro-organisms like bacteria and fungi and protect the
tree.

34. Classification of tannins
 Hydrolyzable tannins: A hydrolyzable tannin is a type of tannin that, on heating
with hydrochloric or sulfuric acids, yields gallic or ellagic acids. They are hydrolyzed
by weak acids or weak bases to produce carbohydrate and phenolic acids. They can
be extracted from different vegetable plants, such as chestnut wood, oak wood etc.
 Non-Hydrolyzable or condensed tannins: Condensed tannins are polymers formed
by the condensation of flavans. They do not contain sugar residues. They are called
proanthocyanidins as they yield anthocyanidins when depolymerized under
oxidative conditions. Different types of condensed tannins exist, such as the
procyanidins, propelargonidins, prodelphinidins, profisetinidins etc.
 Phlorotannins:Phlorotannins are a type of tannins found in brown algae and in a
lower amount also in some red algae. Contrary to hydrolysable or condensed
tannins, these compounds are oligomers of phloroglucinol. These phenolic
compounds are integral structural components of cell walls in brown algae, but
they also seem to play many other secondary ecological roles such as protection
from UV radiation and defense against grazing.

35. Application of Tannins:
 Tannins are an important ingredient in the process of tanning leather. Tanbark
from oak, mimosa and chestnut tree has traditionally been the primary source of
tannery tannin.
 Tannin is a component in a type of industrial particleboard adhesive. Pinus radiata
tannins have been investigated for the production of wood adhesives.
 Tannins can be used for production of anti-corrosive primer for treatment of rusted
steel surfaces prior to painting, rust converter to transform oxidized steel into a
smooth sealed surface and rust inhibitor.
 Tannins in folk medicine are used to combat diarrhoea, hemorrhoids, heal wounds,
as bactericides, other poisons and antidotes.
 The tannins in cranberries have been medically proven to help prevent urinary tract
infections in women by reducing the ability of the bacteria E. coli from adhering to
cells lining the urinary tract.
 Similarly, this anti-adhesive property may reduce the ability of H. pylori to cause
stomach ulcers.
 Recent medical research has also shown that these polyphenolic compounds can
also reduce LDL cholesterol and improve cardiac health.

36. Resins
Resin is amorphous mixtures of essential oils, oxygenated products of terpene and
carboxylic acids. They can be found as exudations from trunk of various trees. In
polymer chemistry, resin is a "solid or highly viscous substance" of plant or synthetic
origin that is typically convertible into polymers. The resins produce in response to
injury and acts as a bandage protecting the plant from invading insects and pathogens.
Notable examples of plant resins include amber, balm of gilead, balsam, dammar gum,
kauri gum etc.
Properties of Resins
 Hard, transparent or translucent brittle materials.
 Resins are bad conductors of electricity and heavier than water.
 On being heated at a relatively low temperature resins first get softened and
ultimately melt down thereby forming either an adhesive or a sticky massive fluid.
 Resins are complex mixtures of resin acids, resin alcohols, resinotannols, esters,
and resenes.
 Can dissolve in alcohol or other organic solvents but insoluble in water.
 Resins do not contain N2 elements and when boiled with alkalis, it yields soaps.

37. Application of resins
Pharmaceutical application
 Resins are local irritant and hence act as local cathartics. (e.g. Jalap and Ipomea)
 Also used in bronchial asthma (e.g. Cannabis)
 Used externally as mild antiseptic in the form of tinctures (Benzoin), ointment and
plasters (Turpentine and Colophony)
 Used in the preparation of emulsion and sustained released formulations.
 Resins have medicinal purposes because of their antihypertensive, analgesic, and
cardioactive properties.
 Podophyllotoxin, from resins in the roots and rhizomes of Podophyllum, is the
starting material for semi synthesis of anticancer compounds.
Other application
 It protects the flower by reflecting light.
 Production of varnishes, adhesives, and food glazing agents.
 Provide constituents of incense and perfume.
 Solid resenes are available as adhesives.