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GLYCOSIDES(ANTHRAQUINONES)

Presented by; M Pharm (Pharmaceutical Chemistry) students Gunturu. Aparna Akshintala. Sree Gayatri Thota. Madhu latha Kamre. Sunil Daram. Sekhar

University College Of Pharmaceutical Sciences Department Of Pharmaceutical Chemistry

Acharya Nagarjuna University Guntur

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Glycosides

Definition: Organic natural compounds present in a lot of

plants and some animals, these compounds upon hydrolysis give one or more sugars (glycone) β- form and non sugar (aglycone) or called genin.

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Glycosides More important in medicine than a lot of

drugs. Occur in higher plant tissues in very

small amounts Also fungal and bacterial cells (exuded

in medium) and animals Formed by a biochemical reaction that

makes a water insoluble compound more polar than a water soluble molecule

Hence can be removed from an organic system

Man forms them in the liver as part of the process of detoxification and they are excreted via urine

Mammalian glycosides are simple compounds whereas plant glycosides are much larger and chemically more complex

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Solubility:

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.

Some glycosides soluble in alcohol.

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Separation between glycosides parts:

Glycosides glycone +aglycone +HCl G + A +salt+H2O

(H2O+G) + A (H2O+G) + (chloroform+A)

We can separate them by using separating funnel.The best solvent to extract aglycone is Ethyl acetate

because:A. Immiscible in water.

B. Always presents in the upper layer.

Neutralization byUsing alkaline Filtration

chloroform

Hydrolysis+HCLdil

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Note: Alcohol and acetone are water

miscible compounds , so we can't use them as organic solvents for aglycone separation.

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Physico-chemical properties of glycosides(general)

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).

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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.

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The function or the role of glycosides in the plant organism

Converting toxic materials to non or less toxic.

Transfer water insoluble substances by using monosaccharide.

Source of energy (sugar reservoir). Storing harmful products such as phenol. Regulation for certain functions(growth). Some have beautiful colours(pollenation

process).

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Some glycosides have antibacterial activity, so they protect the plants from bacteria and diseases.

Bitter almond Amygdalin

bacteria

HCNhydrolysis

kill

Eomlsin enzyme

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Classification of

glycosides

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Classifications of glycosides according to their therapeutic effects

CHF(Congestive Heart Failure)and cardiac muscles stimulators such as:

a. Digitalis glycosides: digoxin, digitoxin, gitoxin (Fox glove leaves).

b. Ouabain: Strophanthus gratus seeds. c. K-strophanthin -Strophanthus kombe seeds. d. Scillaren A,B which isolated from red and white

Squill bulbs. e. Convolloside:Convallaria majalis – Lily of the

Valley.

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Laxative group of glycosides:

a. Sennoside A,B,C,D (Senna leaves and fruits).

b. Cascaroside A,B (Cascara bark).

c. Frangulin and glucofrangulin(Frangula bark).

d. Aloin and barbaloin (Aloe vera and Aloe barbadensis juice).

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Local irritant group: a. Sinigrin (Black mustered seeds-Brassica

nigra) b. Sinalbin (White mustered seeds-Brasica

alba)

Analgesics and antipyretics: Salicin Salisylic acid - Willow or

Salix bark.

Keeping elasticity of blood vessels like:

Rutin -Rutoside (Bitter orange peels, Lemon peels)

Anti-inflammatory group: a. Aloin for 1)acne 2)peptic ulcer b. Glycyrrhizin

hydrolysis

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Classification of glycosides according to glycone part

Glucose -glucoside group like in Sennoside.

Rhamnose -Rhamnoside like in frangullin.

Digitoxose -Digitoxoside like in digoxin.

Glucose and Rhammnose Glucorhamnoside -glucofrangulin.

Rhamnose and glucose - Rhamnoglucoside -Rutin.

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Classification of glycosides on the basis of the linkage between glycone and aglycone part

O-glycosides : In these glycosides the sugar part is linked with a oxygen atom of aglycone .

S-glycosides : In these glycosides the sugar attached to a Sulfur atom of aglycone ,for example sinigrin.

N-glycosides : In these glycosides the sugar linked with Nitrogen atom of (-NH2,-NH-)amino group of aglycone ,for example nucleosides DNA,RNA.

C-glycosides : In these glycosides the sugar linked (condensed) directly to Carbon atom of aglycone ,for example aloin.

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Most of glycoside may be named according to the plant from which they isolated for example:

1. Salicin from salix

2. Cascarosides from cascara

3. Aloin from Aloe vera

4. Sennosides from senna

5. Frangulin from frangula

6. Glycyrrhizin from glycyrrhiza

GENERAL EXTRACTION PROCESS OF GLYCOSIDES;

Always glycosides founded in the plant with the enzymes which hydrolyzed them.

We must damage these enzymes first to extract these glycoside by the following steps:

STEP 1. Drying the plants fresh in special oven at 1000c for 30 minutes.

STEP 2. Boiling them with organic solvents for 20 minutes

STEP 3. Boiling them with acetone 5 minutes

If present in this plant tannins or resins we add lead acetate to precipitate them.

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METHYL GLYCOSIDES

Methylglucoside is a monosaccharide derived from glucose. It can be prepared in the laboratory by the acid-catalyzed reaction of glucose with methanol.

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USES: chemical intermediate in the production of

a variety of products including Emollients. Emulsifiers. humectants. moisturizers. thickening agents. plasticizers. Surfactants. varnishes and resins.

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Preparation of methyl glycoside STEP 1: Methyl glucoside is prepared by the acid-catalyzed reaction

of glucose and methanol .

In the reaction glucose, methanol and acid catalyst, anhydrous hydratable CaSO4  are required .

In the .preparation of methyl glycoside CaSO4 :glucose weight ratio of at least 1:1, maintaining the reaction mixture within the temperature range of about 50°C and 200°C until formation of methyl glucoside ceases.

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cooling the reaction mixture, neutralizing the acid catalyst with a base capable of forming a salt of neutralization which is insoluble in the reaction mixture .

acid catalystC6 H12 O6 +CH3 OH⇋methylglucoside+H2 O (I) 

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2. Process according to step 1, wherein the CaSO4 is incorporated in the reaction mixture in an amount sufficient to provide a CaSO4:glucose weight ratio from about 1:1 to about 3:1

3. Process according to step 1, wherein the CaSO4 :glucose weight ratio is from about 1:1 to about 2:1 

4. Process according to claim 1, wherein the acid catalyst is H2 SO4.

5. Process according to step 4, wherein the base is selected from the group consisting essentially of Ca(OH)2, Mg(OH)2, Ba(OH)2, Sr(OH)2and mixtures there of. 

 6. Process according to step 1, wherein the reaction is carried out in a closed vessel within the temperature range of about 100°C and 150°C

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Anthraquinone Glycosides

(

Anthraquinone Anthraquinone derivatives

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Aloe barbadensis

Cassia senna

Rhamnus purhsianus - Cascara

Rheum palmatum.

Chinese Rhubarb

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Introduction to Anthraquinones Historically: Rhubarb, Senna, Aloes and

Cascara were all used as purgative drugs.

Monocotyledons: Only Liliaceae.Most commonly C-glycoside: barbaloin.

Dicotyledons: Rubiaceae, Leguminosae, Polygonaceae, Rhamnaceae, Ericaceae, Euphorbiaceae, Lythraceae, Saxifragaceae, Scrophulariaceae and Verbenacacea. Also in certain fungi and lichen.

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Reduced derivatives of anthraquinones Oxanthrones, anthranols and anthrones

Compounds formed by the union of 2 anthrone molecules Dianthrones

Aglycones: Chrysophanol/Chrysophanic acid

Rhubarb and Senna. Rhein Rhubarb and Senna Aloe-emodin Rhubarb and Senna Emodin Rhubarb and Cascara

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Anthraquinones – Chemical Properties Anthraquinone derivatives: orange-red compounds Soluble in hot water/dilute alcohol.

Identified via Borntrager’s test

Powdered drug – macerated with ether

Filter

Add ammonia/caustic

Shake pink, red or violet colour – positive for anthraquinone

derivatives

If the Anthraquinones are reduced (within the herb) or stable

(glycosides) test will be negative

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Anthraquinone Structure

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Anthranonls and Anthrones

Reduced anthraquinone derivatives. Occur either freely (aglycones) or as

glycosides. Isomers.

Anthrone: Parent structure (pale yellow, non-soluble in alkali, non-fluorescent)

Anthronol: brown-yellow, soluble in alkali, strongly fluorescent Anthronol derivatives (e.g. in Aloe – have

similar properties – fluorescence used for identification)

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Oxanthrones

Found in Cascara bark Intermediate products (between

anthraquinones and anthranols) When oxidised oxanthrones it form

anthraquinones Oxanthrones are detected by Modified

Borntrager’s Test (oxanthrones oxidised using hydrogen peroxide)

oxanthrone

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Dianthrones Derived from 2 anthrone

molecules 2 molecules may/not be

identical Dianthrones are form easily

due to mild oxidation of anthrones

It form important aglycones Cassia Rheum Rhamnus

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General structure of glycoside

Structure-Activity Relationship

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Glycosylation is essential for activity.

Hydroxylation at C-1 and C-8 is essential for activity.

Oxidation level at C-9 and C-10 is important: Highest level of oxidation (anthraquinones) have the lowest

activity. Oxanthrones are less active than anthrones. Complete reduction of C-9 and C-10 eliminates the activity.

Substitution at C-3 have great impact on activity:

CH2OH > CH3 > COOH

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Mechanism of Action:

The glycosides are absorbed from the small intestine and re-excreted in the large intestine where they increase the motility so produce laxation.

Aglycones produce griping effect so it is recommended to prescripe antispasmodic with them.

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Mechanism of action Molecules have to possess certain

features for activity:[1] glycosides[2] carbonyl keto function on centre ring[3] 1,-8- positions have to have –OH

Potency: anthrone > anthraquinone> dianthrone

Aglycones not therapeutically active in animals , lipid soluble absorbed in stomach and never reach colon to produce a local effect.

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Highly active phenolic group irritant to mucosa

Glycosides very water soluble – reach large intestine where they are hydrolysed by E.coli enzymes and become lipid soluble and absorbed into circulation.

5-8 hours to act take night before

in low doses – drug metabolised by liver and recirculated via bile to give more effect

people especially elderly can become reliant on them needing higher dose to produce an effect

carcinogenic to melanosis coli

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Senna - Leguminosae

Definition: Consists of the dried leaflets of Cassia senna (Alexandrian senna), or Cassia angustifolia (Tinnevelly senna).

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Cassia - Senna

Indigenous to Africa (tropical regions)

Used since 9th and 10th century

Itroduced into medicine by Arab physicians (used both the leaves and pods)

Exported by Alexandria – name of the Sudanese drug.

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Senna - Collection

Collected in September

Whole branches bearing leaves are dried in the sun.

Pods and large stalks are separated with sieves.

Leaves are graded (whole leaves and half-leave mix, siftings).

Whole leaves – sold to public

Rest – used for galenicals.

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Senna - Constituents Senna consist four types of glycosides:

Sennoside A

Sennoside B

Sennoside C

Sennoside D

In their active costituents are sennoside A, sennosides B

Upon hydrolysis of sennosides it gives two molecules glucose+aglycones: Sennidin A and Sennidin B.

Sennoside C & Sennoside D Rhein Aloe-emodin Palmidin A (Rhubarb)

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Senna - Constituents

Kaempferol (yellow flavanol)

+ glucoside (kaempferin)

Mucilage Calcium oxalates Resin

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Comparison of Alexandrian and Tinnevelly Senna

Macroscopical

Seldom larger than 4 cm in length

Grey-green Asymmetric at base

Broken and curled at edges

Few press markings

Macroscopical

Seldom exceeds 5cm in length

Yellow-green Less asymmetric at

base Seldom broken and

normally flat Often shows

impressions (mid vein)

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Comparison between Alexandrian and Tinnevelly Senna

Microscopical

Hairs – numerous (approximately three epidermal cells apart)

Most stomata have two subsidiary cells

Microscopical

Hairs less numerous (approximately six epidermal cells apart)

Stomata have 2-3 subsidiary cells with the respective ratio 7:3

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Comparison between Alexandrian and Tinnevelly Senna

Chemical Tests

Ether extract of hydrolysed acid solution of herb with methanolic magnesioum acetate solution gives

Pink colour in daylight

Pale green-orange colour in filtered UV light

TLC Hydroxymusizin

glycoside present

Chemical Tests

Same Test

Orange colour in daylight

Yellow-green colour in filtered UV light

TLC Tinnevellin glycoside

present

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Senna – Allied Drugs & Substitutes

Allied drugs

Bombay, Mecca and Arabian Sennas (found in Cassia angustifolia from Arabia).

Dog senna – Cassia obovata

Cassia auriculata – Indian Senna

Cassia podocarpa

Substitutes or Adulterants

Argel leaves – Solenostemma argel

Coriario myrtifolia

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Senna Fruit

Definition: Senna pods are the dried, ripe fruits of Cassia senna and Cassia angustifolia, which are commercially known as Alexandrian and Tinnevelly senna pods respectively. Both have separate monographs

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Senna Fruit - Collection Pods are collected with

the leaves and dried in a similar fashion.

After separation of the leaves, the pods are hand-picked into various qualities, the finer being sold (commercially), while the finer pieces are used to make galenicals.

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Senna Fruit - Constituents

Active constituents are found in the pericarp.

Similar to those actives of the leaves Sennoside A Sennidin

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Senna - Uses

Laxatives (habitual constipation or occasional use).

Lacks astringent after-effect (Rhubarb)

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Senna – Additional uses Medicinal Actions Vermifuge, diuretic,

febrifuge

Other uses: laxative candy (bitter taste). Also used to treat

flatulence, gout, fever.

Topically: poultice prepared with vinegar to treat pimples.

NOTE: Senna may cause urine to become reddish – no clinical significance.

Contra-indications Gout, colitis, GI

inflammation.

Should not be used with cardiac glycosides.

Seeds/pods give gentler action than leaves: more appropriate for the young, elderly and those prone to stomach cramps.

NB: Over-use causes dependency.

Overdose: nausea, bloody diarrhoea, vomiting and nephritis.

Long-term use: dehydration & electrolyte depletion, worsening constipation and weakening intestinal muscles.

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Cascara Bark- Rhamnaceae

Definition: Official cascara sagrada is the dried bark of Rhamnus purshianus. Bark is collected from wild trees

(depletion is leading to the increase of cultivation)

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Rhamnus purhsianus - Cascara Etymology

Rhamnos – Greek, branch, shiny shrub. Purshiana after Pursh, botanist 1st described herb in 1814

Other Common Names Bearwood, bitterbark,

buckthorn, coffeeberry, mountain cranberry, persiana, sacred bark.

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Cascara Bark - History

Recently introduced to Modern Medicine.

Known to early Mexican and Spanish priests.

Not introduced to medicine until 1877.

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Cascara – Collection & Preparation Collected form mid-April to

end of August, when it separates readily from the rest of the trunk.

Longitudinal incisions are made 10cm apart and the bark removed.

Tree is then usually felled and the branch bark separated.

Bark is then dried in the shade with the cork facing upwards. This is referred to as ‘natural’ cascara. Commercial supplies are comminuted to give small, even fragments called ‘evenized’, ‘processed’, or ‘compact’ cascara.

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Cascara Bark - Storage

During preparation and storage the bark should be protected from rain and damp (partial extraction of constituents may occur or bark may become mouldy).

Should be stored for at least 1 year before use .

Bark appears to increase in medicinal value up unto its 4 years old (stored bark)

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Cascara Bark – Why Stored for a Year? When stored for at least

a year – better tolerated by patient (less griping pains due to increased peristalsis)

Yet as effective as fresh bark.

Reason? Due to Hydrolysis and other

changes that occur during storage.

Bitter taste of Cascara can also be reduced by treating the bark with alkali (alkali earths or MgO).

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Cascara Bark – Constituents Four main glycosides – Called

Cascarosides Cascaroside A Cascaroside B Cascaroside C Cascaroside D

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Cascara Bark – Constituents

Two aloins: C – Glycosides Breakdown products of Cascarosides A-D

Barbaloin (derived from aloe-emodin) Chrysaloin (derived from chrysopanol

anthrone)

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Cascara Bark – Constituents O-glycosides Derived from

Emodin Emodin oxanthrone Aloe emodin chrysophanol

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Cascara Bark – Constituents

Dianthrones Emodin Aloe-emodin Chrysophanol

Hetrodianthrones Palmidin A, B and C (Rhubarb)

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Cascara Bark - Substitutes Rhamnus alnifolia (too rare)

Rhamnus crocea (bark is very different from official drug)

Rhamnus californica (so closely related to Rhamnus purshianus some botanists do not consider them to be separate species).

Rhamnus fallax

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Cascara Bark - Uses

Purgative Similar to Senna Normally as a tablet Also used on animals

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Cascara Bark – Additional uses

Physiological Action Astringent (bark –

tannins), bitter tonic, chologogue, emetic, hepatic, stomachic.

Medicinal UsesMove stagnation, clear

heat.The most widely used

laxative world-wide.Topically: Used as a wash

for herpes lesions

Excessive use: nausea, vomiting, heamatorrhoea. Long term use: Weakens intestinal muscles.

Contra-indications: children younger than 14, during pregnancy, lactation, IBS, Crohn’s, intestinal obstruction, and idiopathic abdominal pain.

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Rhubarb - Polygonaceae

Definition: Rhubarb/Chinese Rhubarb is the rhizome of Rheum palmatum. Other species and hybrids of Rheum, except R. rhaponticum, may also be included.

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Chinese Rhubarb - History

Chinese Rhubarb has a long history.

Mentioned in a herbal of 2700BC.

Formed an important article of commerce on the Chinese trade routes to Europe.

Still used medicinally today.

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Chinese Rhubarb – Collection & Preparation Rhizomes are grown

at high altitudes (+3000m).

Collected in Autumn or spring (6-10yrs old)

Cork is removed, cut. Artificially dried. Packed in tin-lined

wooden cases. Inferior quality herbs

are packed in hessian bags

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Chinese Rhubarb - Constituents1. Anthraquinones

without a carboxyl group – chrysophanol, emodin, aloe-emodin & physcion.

Also the glycosides of these substances.

2. Anthraquinones with a carboxyl group (rhein and its glycoside: glucorhein).

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Chinese Rhubarb - Constituents3. Anthrones and

dianthrones of chrysophanol, emodin, aloe-emodin or physcoin.

4. Dianthrone glucosides of rhein (Sennosides A and B).

5. Hetrodianthrones derived from 2 different anthrone molecules: Palmidin A and Palmidin B.

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Chinese Rhubarb - Constituents Free

anthraquinones: chrysophanol, emodin, aloe-emodin and rhein.

Some of the above constituents may also occur as glycosides.

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Chinese Rhubarb - Uses

• Bitter stomachic• Diarrhoea (low doses)

– contains tannins• Purgative (high

doses) – followed by an astringent effect.

• Suitable only for occasional for occasional use, not for chronic constipation.

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Rhubarb – Additional Uses

Etymology Rheo – Greek, ‘to flow’,

in reference to the purgative properties.

Medicinal Actions Anti-helminthic, anti-

bacterial, anti-inflammatory, antiseptic, astringent (low doses), sialagoge, vulnerary

Topical Uses: Poultice to treat boils,

burns, wounds. Used to stop bleeding (tannins – stypic and astringent). Used as a mouthwash for oral ulcers.

Other uses: Acid content: fresh root can be used to polish brass.

Caution Leaves should be

avoided – high calcium oxalate - toxic

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Aloe - Liliaceae Definition: Aloes are

the solid residue obtained by evaporating the liquid which drains from the transversely cut leaves of various Aloe species.

The juice is usually concentrated by boiling and solidifies on cooling.

Official varieties are the Cape Aloes from SA and Kenya (Aloe ferox), and the Curacao Aloes from West Indies (Aloe barbadensis).

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Preparation of Cape Aloes

Cape Aloes are prepared from the wild plants of Aloe ferox.

Leaves are cut transversely near the base.

Two hundred leaves arranged around a shallow hole in the ground (lined with canvas or goatskin).

Cut ends overlap & drain into the canvas. After 6hrs all the juice is collected.

Transferred to a drum.

Boiled for 4hrs on an open fire.

Poured into tins while hot solidifies.

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Preparation of Cape Aloes

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Cape Aloes - Characteristics Dark brown or

Green-brown

Glassy masses

Thin fragments have a deep olive colour

Semi-transparent.

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Cape Aloes - Characteristics Powder: green-yellow

When rubbed two pieces of drug together – powder is found on the surfaces.

Characteristic sour odour (rhubarb/apple-tart odour).

Taste: nauseous and bitter.

Microscopy: powder in lactophenol – amorphous.

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Characteristics of Curacao Aloes

Colour: yellow-brown – chocolate brown.

Poor qualities (overheated) black colour.

Opaque Breaks with a waxy

facture Semi-transparent More opaque on keeping. Nauseous and bitter

taste. Characteristic iodoform

odour. Microscopy: lactophenol

– acicular crystals

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Aloes - Constituents

C-glycosides Resins Glycosides

Aloin Barbaloin Isobarbaloin

Aloe-emodin

Cape Aloes: Also Contain

Aloinoside A & Aloinoside B (O-glycosides of barbaloin)

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Aloe - Constituents

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Aloe Constituents & Chemical Tests: Unlike C-glycosides, O-

glycosides of Aloe are not hydrolysed by heating with dilute acids or alkali.

Can be decomposed with ferric chloride & dilute HCl - NB: Modified Borntrager’s Test – oxidative hydrolysis. Anthraquinones give a red colour when shaken with dilute ammonia.

NB: All Aloes give a strong green fluorescence with borax (characteristic of anthranols) - General test for aloes.

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Aloe - Uses

Purgative

Seldom prescribed alone – activity is increased when administered with small quantities of soap or alkaline salts; Carminatives moderate griping tendency.

Ingredient in Friar’s Balsam.

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Aloe – Additional uses

Medicinal Uses: Anti-bacterial, anti-

fungal, chologoge, emmenogogue, anti-inflammatory (juice), anti-inflammatory , demulcent, vulnerary, immune-stimulating (gel).

Radiation burns (internal and external use)

Contra-indicationsPregnancy & lactation

(internal uses)

Etymology Name derives from

Arabic alu, meaning shiny or bitter in reference to the gel.

Other uses Khoi-San hunters rub

gel on their bodies to reduce sweating and mask their scent.

Used to break nail-biting habit.

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Aloe vera Products These are derived

from the mucilage gel – parenchyma cells

Should not be confused with aloes (juice of pericycle – juice used for laxative effect).

Cosmetic industry (usefulness often exaggerated) - Used as suntan lotions, tonics and food additives.

Mucilage = polysaccharide of glucomannans and pectin

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Cochineal

Definition: Cochineal is the dried female insect, Dactylopius coccus, containing eggs and larvae.

Insects are indigenous to Central America, commercial supplies are derived from Peru.

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Cochineal Eggs are protected during

the rainy season are ‘sown’ on cacti – on which it is intended to breed.

Both male and females arise. After a time, fecundation occurs. Females attach themselves to the cacti and the males die out.

Females swell to x2 their original size due to developing larvae & develop red colouring matter.

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Cochineal

Larvae mature after 14days and escape from the now dead body of the parent.

Only a small portion develop into males.

For next 2 weeks, males fly and young females crawl on the plant.

Life cycle = 6 weeks.

3-5 generations may be produced in 1 season

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Cochineal - Collection Insects are brushed from plants with small

brooms and killed (some left to provide for subsequent crops).

First crop killed contains the most colouring matter.

Insects are killed by plunging them in boiling water, stove heat or exposure to fumes by burning sulphur or charcoal.

If heat is used – insects change to purple – black – called ‘black grain’.

Fume killed – turn purple-grey called ‘silver grain’.

Small immature insects and larvae which can be separated by sieves are sold as ‘granilla’ or siftings.

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Cochineal Collection

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Cochineal - Characteristics

Oval in shape Half cm in length

Examined microscopically after removing the colouring matter (ammonia solution).

Each insect contains 60 to 450 eggs and larvae.

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Cochineal - Constituents

C-glycoside example anthraquinone derivative is bright purple, water-soluble colouring matter

Carminic acid Fat Wax Adulteration: occurs by increasing the

weight of the insects by ‘dressing’ it with inorganic matter in a colour which blends in with that of the insect.

Detected when insects are placed in water

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Chemical testBorntrager’s and Modified Borntrager’s

test: For Aglycones: Extract plant material with organic solvent. Shake with NH4OH OR KOH.

For O-Glycosides: Boil plant material with dil. HCl for 10 min, filter and shake

with organic solvent (Ether or Benzene). Separate the organic solvent. Shake with NH4OH OR KOH.

For C-Glycosides: Boil plant material with dil. HCl/FeCl3, filter and shake with

organic solvent (Ether or Benzene). Separate the organic solvent. Shake with NH4OH OR KOH.

Positive result indicated by Rose Red colour in the aqueous alkaline layer.