Secondary Metabolites.pptxjjjjkkkkkkkkkkk

SECONDARY
METABOLITES
Bonthu Devi Priya
Assistant Professor
Maharajah’s college of pharmacy

CONTENT
Definition, Classification, Properties and Identification tests for
1. Alkaloids
2. Glycosides
3. Flavonoids
4. Tannins
5. Volatile oils
6. Resins

INTRODUCTION
Living plants are solar-powered biochemical and biosynthetic
laboratory which manufactures both primary and secondary
metabolites from air, water, minerals and sunlight.
The group of pathways synthesizing simpler but essential molecules
for normal physiological growth and energy requirements of plants is
called primary metabolism and the products are called primary
metabolites.
They are widely distributed in nature and are also utilized as food by
man.
Eg: Sugars, amino acids, coA, mevalonic acid, nucleic acid etc

Secondary metabolites are useless for plants and stored in various
parts of plants restricted in their distribution are derived
biosynthetically from primary metabolites.
These are organic compounds that are not directly involved in the
normal growth, development, or not necessary for the plant cells
themselves but may be useful for the plant as a whole. Since these
don't have primary function so they are called secondary metabolites.
They have Pharmaceutical importance.
Eg: Alkaloids, Glycosides, Flavonoids, Tannins, Volatile oil and
Resins.

ALKALOIDS
DEFINITION
Alkaloids are a class of basic, naturally occurring organic compounds
that contain at least one nitrogen atom.This group also includes some
related compounds with neutral and even weakly acidic properties.
Some synthetic compounds of similar structure may also be termed
alkaloids.
In addition to carbon, hydrogen and nitrogen, alkaloids may also
contain oxygen, sulfur and, more rarely, other elements such as
chlorine, bromine, and phosphorus.

Usually alkaloids are derivatives from amino acids.Even though many
alkaloids are poisonous (e.g. strychnine or coniine), some are used in
medicine as analgesics (pain relievers) or anaesthetics, particularly
morphine and codeine. Most alkaloids have a very bitter taste.
Ex: morphine, strychnine, quinine, ephedrine, and nicotine

CLASSIFICATION
There are three main types of alkaloids:
(1) True alkaloids
(2) Proto alkaloids
(3) Pseudoalkaloids.
True alkaloids and protoalkaloids are derived from amino acids,
whereas pseudoalkaloids are not derived from these compounds.

True alkaloids
True alkaloids derive from amino acid and they share a heterocyclic
ring with nitrogen. These alkaloids are highly reactive substances with
biological activity even in low doses.
The primary precursors of true alkaloids are such amino acids as L-
ornithine, L-lysine, L-phenylalanine/L-tyrosine, L-tryptophan and L-
histidine.
Examples of true alkaloids include such biologically active alkaloids
as cocaine, quinine, dopamine and morphine.

PROTO ALKALOIDS
Protoalkaloids are compounds, in which the N atom derived from an
amino acid is not a part of the heterocyclic. Such kinds of alkaloid
include compounds derived from L-ty-rosine and L-tryptophan.
Proto alkaloids are those with a closed ring, being perfect but
structurally simple alkaloids.
Hordenine, mesca-line and yohimbine are good examples of these
kinds of alkaloid.

PSEUDO ALKALOIDS
Pseudoalkaloids are compounds, the basic carbon skeletons of which
are not derived from amino acids.
In reality, pseudoalkaloids are connected with amino acid pathways.
They are derived from the precursors or post-cursors (derivatives the
indegradation process) of amino acids.
They can also result from the amination and transamination reactions
of the different pathways connected with precursors or post-
cursors of amino acids.

Alkaloids are mainly divided into two categories on the basis of their
chemical structure, that is, heterocyclic rings.
Atypical alkaloids
These are also known as nonheterocyclic alkaloids and contain nitrogen
in aliphatic chain.
Typical alkaloids
These are also known as heterocyclic alkaloids and contain nitrogen in
heterocyclic ring system.

PROPERTIES
Although numerous alkaloids exist, they have similar properties when
separated. In general, they are colourless, crystalline solids which are
basic, have a ring structure, and have definite melting points.
They are also derived from plants and have a bitter taste. However,
some exceptions are known.
For instance, some alkaloids are not basic and others are brightly
coloured (betanidine, beriberine, sangui-narine) or liquid (nicotine).
Other alkaloids are produced synthetically.

Most alkaloids, are also chiral molecules which mean they have
nonsuperimposable mirror images.
This results in isomers that have different chemical properties. For
example, one isomer may have a physiological function while the
other does not.
Generally free bases of alkaloids are soluble in organic solvents and
insoluble in water, where as alkaloidal salts are soluble in water and
partially soluble in organic solvents.
For example, strychnine hydrochloride is much more soluble in water
than strychnine as a base.

CHEMICAL TESTS
The chemical tests are performed from neutral or slightly acidic solution of
drug.
1. Dragendroff's Test
Drug solution + Dragendroff's reagent (Potassium Bismuth lodide), formation
of Orangish red colour.
2. Mayer's Test
Drug solution few drops of Mayer's reagent (potassium mercuric iodide),
formation of creamy-white precipitant.
3. Hager's Test
Drug solution + few drops of Hagers reagent (Saturated aq. Solution of Picric
acid), formation of crystalline yellow precipitate.

4. Wagner's Test
Drug solution + few drops of Wagner's reagent (dilute lodine solution),
formulation of reddish-brown precipitate.
5. Tannic Acid
Test Drug solution few drops of tannic acid solution, formation of buff
coloured precipitate.

GLYCOSIDES
In chemistry, a glycoside is a molecule in which a sugar is bound to
another functional group via a glycosidic bond.
The sugar group is known as the glycone and the nonsugar group as
the aglycone or genin part of the glycoside.
Glycosides play numerous important roles in living organisms.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, making the chemical available for use.
Many such plant glycosides are used as medications.

CLASSIFICATION
The glycosides can be classified by the glycone, by the type of
glycosidal linkage, and by the aglycone.
On the Basis of Glycone - If the glycone group of a glycoside is
glucose, then the molecule is a glucoside; if it is fructose, then the
molecule is a fructoside; if it is glucuronic acid, then the molecule is a
glucuronide, etc.

On the Basis of Glycosidic Linkage
1. O-glycosides: Sugar molecule is combined with phenol or OH group of
aglycon, for example, Amygd-aline, Indesine, Arbutin, Salicin, cardiac
glycosides, anthrax quinone glycosides like sennosides etc.
2. N-glycosides: Sugar molecule is combined with N of the NH (amino group) of
aglycon, for example, nucleosides.
3. S-glycosides: Sugar molecule is combined with the S or SH (thiol group) of
aglycon, for example, Sinigrin.
4. C-glycosides: Sugar molecule is directly attached with C-atom of aglycon, for
example, Anthraquinone glycosides like Aloin, Barbaloin, Cascaroside and
Flavan glycosides

CHEMICAL TESTS
Test A: To about 200mg of extract is boiled with 5ml of dilute H2SO4 on
water bath filter, the filterate is neutralized with 5% NaoH solution and add
1ml of Fehling’s solution A and B and warm it on water bath and note amount
of red precipitate produced by the drug and compare with test B.
Test B: To about 200mg pf extract is boiled with 5ml of water on water bath
filter. The filterate is neutralized with 5% NaoH solution and add 1ml of
Fehlings solution A and B and warm it on water bath and note amount of red
ppt produced by the drug and compare with test A.
Result: The red ppt formed in Test A is greater than Test B that indicates
presence of glycosides.

PROPERTIES
Glycosides are water soluble compounds and insoluble in the organic solvents.
Glycone part: water soluble, insoluble in the organic solvents.
Aglycone part: water insoluble, soluble in the organic solvents.
Glycosides are Colorless, solid, amorphous, nonvolatile (flavonoid- yellow, anthraquinone-
red or orange.
Give positive reaction with Molisch's and Fehling's solution test (after hydrolysis).
They are water soluble compounds, insoluble in organic solvents.
Most of them have bitter taste (except: populin, glycyrrhizin, stevioside).
Odorless except saponin (glycyrrhizin).
when a glycosides has a lot of sugars its solubility in water decrease.
Glycosides hydrolyzed by using mineral acids and temperature or by using enzymes such
as:a- Emolsin Bitter almond seeds.b- Myrosin or Myrosinase black mustard seeds.c-
Rhamnase glycosides containing rhamnose as sugar part.

FLAVONOIDS
Flavonoids (or bioflavonoids; from the Latin word flavus, meaning
yellow, their color in nature) are a class of polyphenolic secondary
metabolites found in plants, and thus commonly consumed in diets.
Chemically, flavonoids have the general structure of a 15-carbon
skeleton, which consists of two phenyl rings (A and B) and a
heterocyclic ring (C, the ring containing the embedded oxygen).
This carbon structure can be abbreviated C6-C3-C6.Flavonoids occur
as aglycones, glycosides, and methylated derivatives.

CLASSIFICATION
According to the IUPAC nomenclature, they can be classified into:
1. Flavonoids or Bioflavonoids
2. Isoflavonoids, derived from 3-phenylchromen-4-one (3-phenyl-1,4-
benzopyrone) structure
3. Neoflavonoids, derived from 4-phenylcoumarine (4-phenyl-1,2-
benzopyrone) structure

CHEMICAL TESTS
Ammonia test
Filter paper dipped in alcoholic solution of drug was exposed to ammonia
vapor. Formation of yellow spot on filter paper.
Shinoda test
To the alcoholic extract of drug magnesium turning and dil. HCI was
added, formation of red colour indicates the presence of flavonoids. To the
alcoholic extract of drug zinc turning and dil. HCI was added, formation of
deep red to magenta colour indicates the presence of dihydro flavonoids.
Vanillin HCI test
Vanillin HCI was added to the alcoholic solution of drug, formation of pink
colour due to presence of flavonoids.

PROPERTIES
Flavonoids are polyphenolic compounds with a C6-C3-C6 skeleton, usually
yellow in color.

They show antioxidant, anti-inflammatory, antimicrobial, and
cardioprotective activities.

They give positive reactions with Shinoda, alkaline reagent, and lead acetate
tests.

In plants, they act as pigments, provide UV protection, and help in defense
against pathogens.

TANNINS
The name tannin is derived from the French taninā (tanning substance) and is
used for a range of natural polyphenols.
Tannins are complex organic, non-nitrogenous plant products, which generally
have astringent properties.
These compounds comprise a large group of compounds that are widely
distributed in the plant kingdom.
The term tannin was first used by Seguin in 1796 to denote substances which
have the ability to combine with animal hides to convert them into leather
which is known as tanning of the hide.
According to this, tannins are substances which are detected by a tanning test
due to its absorption on standard hide powder. The test is known as
Goldbeaters skin test.

CLASSIFICATION
The tannin compounds can be divided into two major groups on the basis of
Goldbeaters skin test.
A group of tannins showing the positive tanning test may be regarded as true
tannins, whereas those, which are partly retained by the hide powder and fail to
give the test, are called as pseudotannins.
Most of the true tannins are high molecular weight compounds. These compounds
are complex polyphenolics, which are produced by polymerization of simple
polyphenols.
They may form complex glycosides or remains as such which may be observed by
their typical hydrolytic reaction with the mineral acids and enzymes.
Two major chemical classes of tannins are usually recognized based on this
hydrolytic reaction and nature of phenolic nuclei involved in the tannins structure.
The first class is referred to as hydrolysable tannins, whereas the other class is
termed as condensed tannins.

Hydrolysable Tannins
As the name implies, these tannins are hydrolysable by mineral acids or
enzymes such as tannase. Their structures involve several molecules of
polyphenolic acids such as gallic, hexahydrodiphenic, or ellagic acids, bounded
through ester linkages to a central glucose molecule.
On the basis of the phenolic acids produced after the hydrolysis, they are further
categorized under gallotannins composed of gallic acid or ellagitannins which
contains hexahydrodiphenic acid which after intraesterification produces ellagic
acid.
Hydrolysable tannins are sometimes referred to as pyrogallol tannins as the
components of phenolic acids on dry distillation are converted to pyrogallol
derivatives. The hydrolysable tannins are soluble in water, and their solution
produces blue colour with ferric chloride.

Nonhydrolysable or Condensed Tannins
Condensed tannins, unlike the previously explained group are not readily
hydrolysable to simpler molecules with mineral acids and enzymes, thus they
are also referred to as nonhydrolysable tannins.
The term proanthocyanidins is sometimes alternatively used for these tannins.
The compounds containing condensed tannins contain only phenolic nuclei
which are biosynthetically related to flavonoids.
When treated with acids or enzymes, they tend to polymerize yielding insoluble
red coloured products known as phlobaphens. The phlobaphens give
characteristic red colour to many drugs such as cinchona and wild cherry bark.
On dry distillation, they yield catechol derivatives.
Condensed tannins are also soluble in water and produces green colour with
ferric chloride.

Pseudotannins
Pseudotannins are simple phenolic compounds of lower molecular
weight.
They do not respond to the tanning reaction of Goldbeaters skin
test.Gallic acid, Chlorogenic acid, or the simple phenolics such as
catechin are pseudotannins which are abundantly found in plants,
especially in dead tissues and dying cells.

PROPERTIES
1) Tannins are colloidal solutions with water.
2) Non crystalline substance.
3) Soluble in water (exception of some high molecular weight structures), alcohol,
dilute alkali, and glyc-erin.
4) Sparingly soluble in ethyl acetate.
5) Insoluble in organic solvents, except acetone.
6) Molecular weight ranging from 500 to >20,000.
7) Oligomeric compounds with multiple structure units with free phenolic groups.
8) Can bind with proteins and form insoluble or soluble tannin protein complexes.

CHEMICAL TESTS
1. Goldbeaters skin test: Goldbeaters skin is a membrane produced from the
intestine of Ox. It behaves just like untanned animal hide. A piece of
goldbeaters skin previously soaked in 2% hydrochloric acid and washed with
distilled water is placed in a solution of tannin for 5 minutes. It is then
washed with distilled water and transferred to 1% ferrous sulphate solution. A
change of the colour of the goldbeaters skin to brown or black indicates the
presence of tannin.
2. Hydrolysable and condensed tannins both give the positive goldbeaters test,
whereas pseudotannins show very little colour or negative test.

3. Phenazone Test: To 5 ml of aqueous solution of tannin containing drug,add
0.5 g of sodium acid phosphate. Warm the solution, cool, and filter. Add 2%
phenazone solution to the filtrate. All tannins are precipitated as bulky,
coloured precipitate.
4. Gelatin Test: To a 1% gelatine solution, add little 10% sodium chloride. If a
1% solution of tannin is added to the gelatine solution, tannins cause
precipitation of gelatine from solution.
5. Test for Catechin (Matchstick Test): Catechin test is the modification of the
well-known phloroglucinol test for lignin. Matchstick contains lignin. Dip a
matchstick in the dilute extract of the drug, dry, moisten it with concentrated
hydrochloric acid, and warm it near a flame. Catechin in the presence of acid
produces phloroglucinol which stains the lignified wood pink or red.

6. Test for chlorogenic acid: A dilute solution of chlorogenic acid containing
extract, if treated with aqueous ammonia and exposed to air, slowly turns green
indicating the presence of chlorogenic acid.
7. Vanillin-hydrochloric acid test: Drug shows pink or red colour with a
mixture of vanillin: alcohol dilute HCI in the ratio 1:10:10. The reaction
produces phloroglucinol which along with vanillin gives pink or red colour.

VOLATILE OILS
Volatile oils are odorous volatile principles of plant and animal source,
evaporate when exposed to air at ordinary temperature, and hence known as
volatile or etheral oils.
These represent essence of active constituents of the plant and hence also
known as essential oils.
In most instances the volatile oil preexists in the plant and is usually
contained in some special secretory tissues, for example, the oil ducts of
umbelliferous fruits, the oil cells, or oil glands occurring in the sub-
epidermal tissue of the lemon and orange, mesophyll of eucalyptus leaves,
trichomes of several plants, etc.

CLASSIFICATION
S.No. Class Examples
1 Hydrocarbon Volatile oil Terpentine, Black pepper
2 Aldehyde volatile oil Cinnamon, bitter almond, bitter
orange peel
3 Alcohol volatile oil Coriander
4 Ketone volatile oil Cumin
5 Phenol volatile oil Clove bud, Tulasi, ajowan
6 Phenolic ether volatile oil Fennel, anise
7 Ester volatile oil Garlic

PROPERTIES
Volatile oils are freely soluble in ether and in chloroform and fairly soluble in
alcohol; they are insoluble in water.
The volatile oils dissolve many of the proximate principles of plant and animal
tissues, such as the fixed oils and fats, resins, camphor, and many of the
alkaloids when in the free state.These are chemically derived from terpenes
(mainly mono and sesqui terpenes) and their oxygenated derivatives.
These are soluble in alcohol and other organic solvents, practically insoluble in
water, lighter than water (Clove oil heavier), possess characteristic odour, have
high refraction index, and most of them are optically active.
Volatile oils are colourless liquids, but when exposed to air and direct sunlight
these become darker due to oxidation. Unlike fixed oils, volatile oils neither
leave permanent grease spot on filter paper nor saponified with alkalis.

CHEMICAL TESTS
Natural drugs containing volatile oils can be tested by following
chemical tests:
1. Thin section of drug on treatment with alcoholic solution of Sudan
III develops red colour in the presence of volatile oils.
2. Thin section of drug is treated with tincture of alkana, which
produces red colour that indicates the presence of volatile oils
in natural drugs.

RESINS
Definition
Resin can be defined as the complex amorphous product of more or less
solid characteristics which on heating first sets softened and then melt.
Resins are produced and stored in the schizogenous or schizolysigenous
glands or cavities of the plants.
Isolated resin products which comè as an unorganized crude drug in the
market are more or less solid, hard, transparent, or translucent materials.
Resins are insoluble in most polar and nonpolar solvents like water and
petroleum ether, respectively, but dissolve completely in alcohol, solvent
ether, benzene, or chloroform.

CLASSIFICATION
Resins are classified mostly on the basis of two important features, that is, on the
basis of their chemical nature and secondly as per their association with the other
group of compounds like essential oils and gums.
1. Resin Acids
Resin acids are the carboxylic acid group containing resinous substances which
may or may not have association with phenolic compounds.These compounds
are found in free states or as the esters derivatives.
Being acidic compounds they are soluble in aqueous solution of alkalies
producing frothy solution.
Resin acids can be derivatized to their metallic salts known as resinates, which
finds their use in soap, paints and varnish industries.
The abietic acid and commiphoric acid present in colophony and myrrh
respectively are the examples of resin acids.

2. Resin Esters
Resin esters are the esters of the resin acids or the other aromatic acids like benzoic,
cinnamic, salicylic acids, etc.They are sometimes converted to their free acids by the
treatment with caustic alkali. Benzoin is the common resin ester containing drugs.
3. Resin Alcohols
Resin alcohols or resinols are the complex alcoholic com-pounds of high molecular
weight. Like resin acids they are found as free alcohols or as esters of benzoic, salicylic,
and cinnamic acids. They are insoluble in aqueous alkali solution but are soluble in alcohol
and ether. Resinols are present in benzoin as benzoresinol and in storax as storesinol.
4.Resin Phenols
Resin phenols or resinotannols are also high molecular weight compounds which occur in
free states or as esters. Due to phenolic group they form phenoxoids and become soluble in
aqueous alkali solution. However they are insoluble in water but dissolve in alcohol and
ether. Resinotannols gives a positive reaction with ferric chloride. The resinotannol are
found in balsam of Peru as peruresinotannol, in Tolu balsam as toluresinotannol and in
benzoin as siaresinotannols.

5. Glucoresins
Resins sometimes get combined with sugars by glycosylation and produce
glucoresins. Glycoresins can be hydrolysed by acidic hydrolysis to the
glycone and aglycone.
6. Resenes
Chemically inert resin products are generally termed as resenes. They are generally
found in free state and never form esters or other derivatives. Resenes are soluble in
benzene, chloroform and to some extent in petroleum ether. Resenes are insoluble in
water. Asafoetida is an example of resene-containing drug, which contains drug
about 50% of asaresene B. Accordingly, other simple classification based on the
association of resin with gums and/or volatile oils is given below.
7. Oleoresins
Oleoresins are the homogenous mixture of resin with vola-tile oils. The oleoresins
posses an essence due to volatile oils. A trace amount of gummy material may
sometimes be found in oleoresins. Turpentine, ginger, copaiba, Canada resin are few
important examples of oleoresins.

8. Gum Resins
Gum resins are the naturally occurring mixture of resins with gums. Due to
solubility in water, gums can be easily separated out from resin by dissolving the
gum in water. Ammoniacum is an example of natural gum resin.
9. Oleogum Resins
Oleogum resins are the naturally occurring mixtures of resin, volatile oil, and
gum. The example includes gum myrrh, asafoetida, gamboage, etc. Oleogum
resins oozes out from the incisions made in the bark and hardens.
10.Balsams
Balsams are the naturally occurring resinous mixtures which contain a high
proportion of aromatic balsamic acids such as benzoic acid, cinnamic acid, and
their esters. Balsams containing free acids are partially soluble in hot water. Some
important balsams containing drugs are balsam of Peru, balsam of Tolu, benzoin,
and storax. The oleogum resin containing drugs like copaiba and Canada are
sometimes wrongly referred to as balsams.

PROPERTIES
Insoluble in water and petroleum ether dissolved, more and less
completely alcohol, ether and chloroform.
Chemically resin are complexe mixture of resin acid, resin alcohol
(resinols), resin phenol (resin otannols) ester and chemically inert
compound known as resenes.
Resins are often associated with volatile oil (oleoresins), with gums
(gum resins) or with oil and gum (oleo-gum-resins).
Resins do not contain nitrogen element.
Balsams are resinous mixture that contain large properties of cinnomic
acid, benzoic acid or both or esters of these acid.

CHEMICAL TESTS
Physical Test:- solubility, taste, odor and examination of powder under
themicroscope.
Chemical Test:- For the identification of resins, acid value,
saponification value, iodine value.
Specific Chemical Test :- for specific constitution such as cinnamic
acid, benzoic acid in benzoin tolu balsam and peur balsom.

SPECIFIC CHEMICAL TESTS
Identification Test Reagents Used Positive result Compound positive for
the test
HCL test HCl Pink colour Presence of resins
Fecl3 test Fecl3 Greenish blue colour Presence of resins
Umbelliferone
test(specific test for
asafoetida)
Hcl+conc. NH4OH,
HNO3, H2SO4 washed
with water.
Blue fluorescence Green,
red and violet colour
Umbelliferone
Coppee acetate Test Petroleum test Emerald green Abletic acid
Test for
Aspidium(oleoresin)
Diluted alcohol solution +
FeCl3
Green colour Filmarone, flavaspidinol,
flavaspidic acid
Test for myrrh(oleo-gum-
resin)
Ether + HNO3 + Br2
vapour
Purplish violet Commiphoric acid

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