UNIT – II -Part 2
Secondary Metabolites: General Introduction, Composition, Chemistry, Chemical Classes, Bio-sources, Therapeutic Uses & Commercial Applications
SYLLABUS COVERAGE
Phenylpropanoids & Flavonoids — Lignans, Tea, Ruta
Steroids, Cardiac Glycosides & Triterpenoids — Liquorice, Dioscorea, Digitalis
Volatile Oils — Mentha, Clove, Cinnamon, Fennel, Coriander
Tannins — Catechu, Pterocarpus
Resins — Benzoin, Guggul, Ginger, Asafoetida, Myrrh, Colophony
Glycosides — Senna, Aloe, Bitter Almond
Iridoids, Other Terpenoids & Naphthaquinones — Gentian, Artemisia, Taxus, Carotenoids
RUTA
Synonym
Garden Rue; Common Rue
Biological Source
Ruta consists of the dried leaves of Ruta graveolens Linn.
Family
Rutaceae
Description
It is a small, perennial and aromatic plant.
The plant grows up to about 1 metre in height.
Leaves are bluish-green and divided into small leaflets.
The leaves contain oil glands and have a strong, characteristic odour.
Flowers are small and yellow and occur in clusters.
The fruit is a capsule containing black seeds.
Chemical Constituents
The main chemical constituents are:
Flavonoids: Rutin
Alkaloids: Skimmianine and graveoline
Volatile oil: Mainly contains 2-undecanone (methyl nonyl ketone)
Coumarins and furanocoumarins
Tannins and other phenolic compounds
Chemical Tests
1. Lead Acetate Test
Procedure: Prepare an extract of the drug and add lead acetate solution.
Result: A yellow precipitate is formed.
Indication: It indicates the presence of phenolic/flavonoid constituents.
2. Ferric Chloride Test
Procedure: Add a few drops of ferric chloride solution to the suitable extract.
Result: A greenish or bluish-green colour develops.
Indication: It indicates the presence of phenolic compounds.
Uses
Traditionally used as an antispasmodic — helps reduce spasms or cramps (ऐंठन कम करने वाला).
Used as a carminative — helps relieve gas and abdominal discomfort (गैस कम करने वाला).
Traditionally used for some menstrual complaints.
The strong-smelling plant has been used as an insect repellent.
Rutin has antioxidant properties.
Caution: Rue can be toxic in large amounts and should not be used internally during pregnancy.
Important Note
Ruta graveolens may cause photodermatitis — a skin reaction that may occur after contact with the plant followed by exposure to sunlight (धूप से होने वाली त्वचा की प्रतिक्रिया). Therefore, it should be handled carefully.
3. STEROIDAL, CARDIAC AND TRITERPENOID GLYCOSIDES
Introduction
Glycosides are compounds made up of two parts:
Sugar part → Glycone
Non-sugar part → Aglycone or Genin — the non-sugar part (शर्करा रहित भाग).
Cardiac glycosides contain a steroidal nucleus and a lactone ring. They are mainly known for their action on the heart.
The steroid part is based on the cyclopentanoperhydrophenanthrene nucleus.
Basic Structure of Cardiac Glycosides
A cardiac glycoside mainly contains:
Steroidal nucleus
Lactone ring at C-17
Sugar part at C-3
The aglycone is mainly responsible for the pharmacological action, while the sugar part affects properties such as absorption and distribution.
Two Structural Types
| Type | Lactone Ring | Example |
|---|---|---|
| Cardenolide | 5-membered unsaturated lactone ring at C-17 | Digoxin, Digitoxin |
| Bufadienolide | 6-membered doubly unsaturated lactone ring at C-17 | Bufalin |
Cardenolides
Have a 5-membered unsaturated lactone ring.
They are commonly found in plants.
Examples: Digoxin and Digitoxin.
Bufadienolides
Have a 6-membered doubly unsaturated lactone ring.
They are found mainly in toad venom and some plants.
Example: Bufalin.
Structure–Activity Relationship of Cardiac Glycosides
The following structural features are important for cardiac activity:
The steroidal nucleus is important for activity.
The lactone ring at C-17 is essential for cardiac activity.
The lactone ring is attached at C-17β.
The sugar part is generally attached at C-3β.
The A/B ring junction is generally present in the cis configuration in active natural cardiac glycosides.
The C/D ring junction is also generally cis.
The unsaturated lactone ring is important for cardiac activity.
The sugar part affects solubility, absorption, distribution and elimination.
Hydroxyl groups (–OH) affect the polarity and duration of action of the glycoside.
Important Point
Aglycone → Mainly responsible for pharmacological activity
Sugar part → Mainly affects pharmacokinetic properties — how the drug is absorbed, distributed and removed from the body (शरीर में दवा के अवशोषण, वितरण और निष्कासन से संबंधित).
Key Identification Tests
| Test | Detects | Positive Result |
|---|---|---|
| Baljet's Test | Unsaturated lactone ring | Orange to orange-red colour |
| Kedde's Test | Unsaturated lactone ring | Purple/violet colour |
| Legal's Test | Unsaturated lactone ring | Pink to red colour |
| Liebermann–Burchard Test | Steroidal nucleus | Green or blue-green colour |
| Keller–Kiliani Test | 2-Deoxy sugar | Brown/reddish-brown ring at the junction |
1. Baljet's Test
Procedure: Treat the drug extract with sodium picrate solution.
Result: Orange to orange-red colour develops.
Indication: Presence of an unsaturated lactone ring — a special ring structure associated with cardiac activity (विशेष रिंग संरचना).
2. Kedde's Test
Procedure: Treat the drug extract with 3,5-dinitrobenzoic acid and alkali.
Result: Purple or violet colour develops.
Indication: Presence of an unsaturated lactone ring.
3. Legal's Test
Procedure: Treat the drug extract with sodium nitroprusside and alkali.
Result: Pink to red colour develops.
Indication: Presence of an unsaturated lactone ring.
4. Liebermann–Burchard Test
Procedure: Treat the drug extract with acetic anhydride and concentrated sulphuric acid.
Result: Green or blue-green colour develops.
Indication: Presence of a steroidal nucleus.
5. Keller–Kiliani Test
Procedure: Add glacial acetic acid containing ferric chloride to the drug extract and carefully add concentrated sulphuric acid.
Result: A brown or reddish-brown ring appears at the junction of the two layers.
Indication: Presence of 2-deoxy sugars, such as digitoxose. A 2-deoxy sugar is a sugar having a missing oxygen-containing group at a specific position (विशेष प्रकार की शर्करा).
LIQUORICE
Synonym
Mulethi; Licorice
Biological Source
Liquorice consists of the dried peeled or unpeeled roots and stolons of Glycyrrhiza glabra Linn.
The important commercial types include:
Spanish liquorice
Russian liquorice
Family
Leguminosae (Fabaceae)
Macroscopy
Peeled drug: Pale yellow in colour.
Unpeeled drug: Yellowish-brown externally and yellowish internally.
Shape: Usually cylindrical and slightly irregular.
Pieces may be about 20 cm long and 1–2 cm in diameter.
Bark: Fibrous.
Fracture: Splintery.
Odour: Faint and characteristic.
Taste: Sweet.
Chemical Constituents
Glycyrrhizin (glycyrrhizic acid) is the chief constituent.
It is a pentacyclic triterpenoid saponin — a plant compound that can produce foam with water (झाग बनाने वाला पौधीय यौगिक).
Glycyrrhizin occurs mainly as potassium and calcium salts of glycyrrhizic acid.
On hydrolysis, glycyrrhizin gives glycyrrhetinic acid + two molecules of glucuronic acid.
Flavonoids: Liquiritin and isoliquiritin.
These flavonoids contribute to the yellow colour of liquorice.
Glycyramarin is a bitter principle present in the resin.
Carbenoxolone is an anti-ulcer compound prepared from liquorice-derived material.
Chemical Test
Sulphuric Acid Test
Procedure: Treat a section of the drug with 80% sulphuric acid (H₂SO₄).
Result: A deep yellow colour develops.
Indication: This colour reaction supports the identification of liquorice.
Uses
Demulcent — soothes irritated mucous membranes (जलन वाली सतह को शांत करने वाला).
Expectorant — helps in removal of mucus from the respiratory tract (बलगम निकालने में सहायक).
Used as a flavouring agent in pharmaceutical preparations.
Traditionally used for gastric irritation and peptic ulcer preparations.
Used as a mild laxative in some traditional preparations.
DIOSCOREA
Synonym
Yam; Wild Yam
Biological Source
Dioscorea consists of the dried tubers of Dioscorea deltoidea Wall.
Family
Dioscoreaceae
Macroscopy
Tubers are cylindrical or globose and vary in size.
Colour: Light brown.
Odour: Odourless.
Taste: Bitter.
The drug consists mainly of dried pieces of the tuber.
Chemical Constituents
The tubers contain about 75% starch.
The chief active constituent is diosgenin, a steroidal sapogenin — the non-sugar steroid part obtained from certain saponins (सैपोनिन का steroid वाला भाग).
Other steroidal sapogenins include:
Smilagenin
Epismilagenin
Yammogenin
Diosgenin is obtained mainly by hydrolysis of the saponin dioscin.
Dioscin + acid hydrolysis → Diosgenin + 2 L-rhamnose + 1 D-glucose
The tubers also contain the enzyme sapogenase.
Uses
Diosgenin is an important starting material for the industrial preparation of steroidal drugs.
It is used in the manufacture of:
Corticosteroids
Sex hormones
Oral contraceptives
Dioscorea has also been used traditionally for rheumatic complaints.
DIGITALIS
Synonym
Foxglove Leaves
Biological Source
Digitalis consists of the dried leaves of Digitalis purpurea Linn. and Digitalis lanata J.F. Ehrh.
Family
Plantaginaceae
Digitalis was formerly included in the family Scrophulariaceae.
Standard
The drug should contain not less than 0.3% total cardenolides, calculated as digitoxin.
Leaves are dried at a temperature below 60°C soon after collection to prevent decomposition of the active constituents.
Moisture content should not exceed 5%.
Macroscopy
Colour: Upper surface deep green to greyish-green; lower surface greyish-green.
Shape: Ovate-lanceolate to broadly ovate.
Size: About 10–30 cm long and 4–10 cm wide.
Margin: Crenate-dentate (with teeth along the leaf margin).
Venation: Pinnate.
Odour: Characteristic.
Taste: Bitter.
Microscopy
The leaf is dorsiventral — the upper and lower surfaces have different structures (ऊपरी और निचली सतह की बनावट अलग होती है).
Stomata: Mainly anomocytic.
Covering trichomes: Uniseriate and multicellular, usually containing 2–7 cells.
Glandular trichomes: Have a unicellular stalk and bicellular head.
Collapsed-cell trichomes are a characteristic feature.
Calcium oxalate crystals are absent.
Sclerenchymatous cells (stone cells) are absent.
Chemical Constituents
Digitalis contains about 0.2–0.45% cardiac glycosides.
Primary glycosides: Purpurea glycoside A and Purpurea glycoside B.
These contain three digitoxose sugars and one terminal glucose.
Important secondary glycosides include:
Digitoxin
Gitoxin
Gitaloxin
Hydrolysis of Primary Glycosides
| Glycoside | Products on Hydrolysis |
|---|---|
| Purpurea glycoside A | Digitoxigenin + 3 digitoxose + glucose → Digitoxin |
| Purpurea glycoside B | Gitoxigenin + 3 digitoxose + glucose → Gitoxin |
Digitalis lanata — Allied Drug
Digitalis lanata is more potent than Digitalis purpurea.
It contains acetylated digitoxose in its primary glycosides.
Important constituents include Lanatosides A, B, C, D and E.
Lanatoside C gives Digoxin on hydrolysis.
Digoxin is an important cardiac glycoside used clinically.
Important Constituents
| Lanatoside | Corresponding Cardiac Glycoside |
|---|---|
| Lanatoside A | Digitoxin |
| Lanatoside B | Gitoxin |
| Lanatoside C | Digoxin |
| Lanatoside D | Diginatin |
| Lanatoside E | Gitaloxin |
On hydrolysis, these compounds give the corresponding cardenolide along with 3 digitoxose, 1 acetylated digitoxose and 1 glucose.
Substitute / Confusable Leaves
1. Mullein Leaves — Verbascum thapsus
Characterised by branched candelabra-type trichomes.
2. Comfrey Leaves — Symphytum officinale
Have multicellular trichomes with a hooked tip.
3. Primrose Leaves — Primula vulgaris
Have uniseriate covering trichomes.
Chemical Tests
| Test | Observation |
|---|---|
| Keller–Kiliani Test | Reddish-brown ring at the junction with a bluish-green upper layer |
| Legal's Test | Pink to red colour |
| Baljet's Test | Yellow to orange colour |
| Raymond's Test | Violet colour |
| Kedde's Test | Blue to violet colour |
| Antimony Trichloride Test | Blue colour |
1. Keller–Kiliani Test
Procedure: Treat the drug extract with glacial acetic acid containing ferric chloride and carefully add concentrated sulphuric acid.
Result: A brown or reddish-brown ring develops at the junction of the two layers.
Indication: Presence of 2-deoxy sugar, particularly digitoxose.
2. Legal's Test
Procedure: Treat the extract with sodium nitroprusside and alkali.
Result: Pink to red colour develops.
Indication: Presence of an unsaturated lactone ring.
3. Baljet's Test
Procedure: Treat the drug extract with sodium picrate.
Result: Yellow to orange colour develops.
Indication: Presence of an unsaturated lactone ring.
4. Raymond's Test
Procedure: Treat the drug extract with m-dinitrobenzene and alkali.
Result: Violet colour develops.
Indication: Presence of an unsaturated lactone ring.
5. Kedde's Test
Procedure: Treat the drug extract with 3,5-dinitrobenzoic acid and alkali.
Result: Blue to violet colour develops.
Indication: Presence of an unsaturated lactone ring.
6. Antimony Trichloride Test
Procedure: Treat the suitable extract with antimony trichloride reagent.
Result: Blue colour develops.
Indication: Supports the presence of cardiac glycoside constituents.
Uses
Digitalis increases the force of contraction of the heart and acts as a cardiotonic.
It has been used in the management of certain forms of heart failure.
Digoxin is used in selected patients with atrial fibrillation and atrial flutter, mainly to help control the heart rate.
Digitalis is a potent drug and must be used under proper medical supervision.
4. VOLATILE OILS
Introduction
Volatile oils, also called essential oils, are odorous substances obtained mainly from plants. They evaporate easily when exposed to air at ordinary temperature.
They are responsible for the characteristic smell and aroma of many medicinal plants.
Most volatile oils contain terpenes and their oxygenated derivatives.
Terpenes are made from isoprene units (C₅H₈). An isoprene unit is the basic five-carbon building block of many terpenes (मुख्य 5-carbon building block).
Classification Based on Number of Isoprene Units
| Class | Number of Isoprene Units | Formula |
|---|---|---|
| Hemiterpene | 1 | C₅H₈ |
| Monoterpene | 2 | C₁₀H₁₆ |
| Sesquiterpene | 3 | C₁₅H₂₄ |
| Diterpene | 4 | C₂₀H₃₂ |
| Triterpene | 6 | C₃₀H₄₈ |
| Tetraterpene (Carotenoid) | 8 | C₄₀H₆₄ |
| Polyterpene (Rubber) | Many | (C₅H₈)ₙ |
Classification Based on Functional Group
| Class | Example Drugs |
|---|---|
| Aldehyde oils | Bitter almond, bitter orange peel, lemon peel, lemon grass, cinnamon, citronella |
| Alcohol oils | Coriander, peppermint, sandalwood, cardamom |
| Hydrocarbon oils | Black pepper, turpentine |
| Ketone oils | Buchu, caraway, cumin, camphor, dill, jatamansi, musk, spearmint |
| Phenolic ether oils | Anise, calamus, fennel, nutmeg |
| Oxide oils | Chenopodium, eucalyptus |
| Ester oils | Gaultheria, lavender, mustard |
Identification Tests for Terpenes
| Test | Method | Observation |
|---|---|---|
| Salkowski Test | Drug + chloroform (CHCl₃) + concentrated H₂SO₄ | Yellow colour changes to red |
| Noller Test | Drug + SnCl₂ in thionyl chloride (SOCl₂) | Red colour |
| Antimony Trichloride Test | SbCl₃ in chloroform followed by the specified reagent | Orange-red colour |
1. Salkowski Test
Procedure: Dissolve the drug or volatile oil in chloroform and carefully add concentrated sulphuric acid.
Result: A yellow colour develops, which may change to red.
Indication: Indicates the presence of terpenoid constituents.
2. Noller Test
Procedure: Treat the drug or volatile oil with stannous chloride (SnCl₂) in thionyl chloride (SOCl₂).
Result: Red colour develops.
Indication: Indicates the presence of terpenoid constituents.
3. Antimony Trichloride Test
Procedure: Treat the sample with antimony trichloride (SbCl₃) in chloroform and carry out the specified colour reaction.
Result: Orange-red colour develops.
Indication: Indicates the presence of terpenoid constituents.
MENTHA OIL
Synonym
Peppermint Oil
Biological Source
Mentha oil is obtained by steam distillation of the fresh flowering tops of Mentha × piperita L.
The two commonly mentioned forms are:
White mint
Black mint
Family
Labiatae (Lamiaceae)
Chemical Constituents
The chief constituent is l-menthol, present in free and esterified forms.
Menthol may constitute about 50–70% or more of the oil, depending on the variety and source.
Other constituents include:
l-Limonene
1,8-Cineole (eucalyptol)
α-Pinene
β-Pinene
Camphene
Menthofuran
Menthone is also an important constituent of peppermint oil.
Menthofuran can contribute to an undesirable odour and may promote resinification during storage.
Esters and other minor constituents contribute to the characteristic flavour and aroma.
Uses
Used as a carminative — helps relieve gas and abdominal discomfort (गैस कम करने वाला).
Used as a flavouring agent in toothpaste, chewing gum, candies and pharmaceutical preparations.
Used in perfumes and cosmetic preparations.
Menthol produces a cooling sensation and has mild local analgesic and soothing effects.
Peppermint oil can produce antispasmodic action by relaxing smooth muscle (मांसपेशियों की ऐंठन कम करने वाला).
Used in some preparations for indigestion and minor digestive discomfort.
Used in lozenges and inhalation preparations for its cooling and soothing effect.
CLOVE
Biological Source
Clove consists of the dried flower buds of Syzygium aromaticum (L.) Merr. & L.M. Perry.
Eugenia caryophyllus is an older botanical name.
Family
Myrtaceae
Macroscopy
Colour is dark brown to reddish-brown.
Odour is strong, aromatic and characteristic.
Taste is pungent, followed by a numbing sensation on the tongue.
The drug consists of a stalk (hypanthium) with four sepals and a dome-shaped unopened corolla.
The upper part has four calyx teeth.
Microscopy
Epidermis has a thick cuticle.
Anomocytic stomata are present.
Schizolysigenous oil glands are present and contain volatile oil.
Calcium oxalate crystals occur in clusters.
The central region contains a columella surrounded by aerenchymatous tissue.
Chemical Constituents
Contains about 14–21% volatile oil.
Contains about 10–13% tannins.
Other constituents include resin, oleanolic acid and vanillin.
The volatile oil mainly contains:
Eugenol — about 80–95%
Acetyl eugenol
α-Caryophyllene and β-caryophyllene
Eugenol is the main constituent responsible for the characteristic aroma and many of the medicinal properties of clove.
Adulterants / Substitutes
1. Mother Cloves
These are mature fruits of the clove plant.
They are dark brown and have an ovate shape.
They contain less volatile oil than normal cloves.
2. Clove Stalks
Consist mainly of the stalks of the flower buds.
Show isodiametric sclereids and calcium oxalate crystals.
Contain much less volatile oil than cloves.
3. Blown Cloves
These are opened flowers in which the stamens have become visible or detached.
They contain less oil than unopened flower buds.
4. Exhausted Cloves
These are cloves from which most of the volatile oil has already been removed by distillation.
They are usually dark, shrunken and lighter than normal cloves.
Chemical Tests
1. Sodium Hydroxide Test
Procedure: Prepare a chloroform extract of clove and treat it with 30% sodium hydroxide solution saturated with sodium bromide.
Result: Needle- or pear-shaped crystals of sodium eugenate may form in rosette-like groups.
Indication: Presence of eugenol.
2. Potassium Hydroxide Test
Procedure: Treat a section of the hypanthium with 50% potassium hydroxide solution.
Result: Needle-shaped crystals of potassium eugenate are formed.
Indication: Presence of eugenol.
Uses
Used as an aromatic stimulant and spice.
Important source of eugenol-rich volatile oil.
Used as a carminative — helps relieve gas (गैस कम करने वाला).
Eugenol has antiseptic and local analgesic properties.
Clove oil is traditionally used for toothache as a topical preparation.
Eugenol is used with zinc oxide in some temporary dental filling materials.
CINNAMON
Cinnamon consists of the dried inner bark of Cinnamomum verum J.Presl.
It was formerly known as Cinnamomum zeylanicum.
Family
Lauraceae
Macroscopy
Outer surface: Dull yellowish-brown.
Inner surface: Dark yellowish-brown.
Odour: Strong, fragrant and characteristic.
Usually occurs as compound quills — thin pieces of bark rolled together (लपेटी हुई छाल).
Quills may be about 1 metre long and approximately 1 cm in diameter.
Bark is about 0.5 mm thick.
Taste: Aromatic and sweet, followed by a warm sensation.
Microscopy
Since cinnamon consists mainly of the inner bark, the cork and primary cortex are absent.
The main region contains:
Phloem
Phloem fibres
Biseriate medullary rays
Starch grains are present.
Calcium oxalate crystals are also present.
Chemical Constituents
Contains about 0.5–1.0% volatile oil.
Contains about 1–2% tannins, mainly phlobatannins.
Other constituents include:
Mucilage
Calcium oxalate
Starch
Mannitol
The volatile oil mainly contains:
Cinnamaldehyde — about 60–70%
Eugenol — about 5–10%
Benzaldehyde
Cumin aldehyde
Phellandrene
Pinene
Cymene
Caryophyllene
Chemical Test
Ferric Chloride Test
Procedure: Treat the volatile oil with ferric chloride solution.
Result: Cinnamon oil gives a pale green colour.
Reason:
Cinnamaldehyde gives a brown colour.
Eugenol gives a blue colour.
The combination produces a pale green colour.
Distinction from Cassia
Cinnamon oil contains both cinnamaldehyde and eugenol, whereas cassia oil contains mainly cinnamaldehyde and little or no eugenol.
Therefore:
Cinnamon oil + FeCl₃ → pale green colour
Cassia oil + FeCl₃ → brown colour
Uses
Used as a carminative — helps relieve gas (गैस कम करने वाला).
Used as a stomachic — helps improve digestion (पाचन में सहायक).
Used as a mild astringent — causes slight tissue contraction (सिकुड़न पैदा करने वाला).
Used as a flavouring agent.
Used as an aromatic stimulant.
Cinnamon oil has antimicrobial properties and is used in some pharmaceutical and oral-care preparations.
FENNEL
Biological Source
Fennel consists of the dried ripe fruits of Foeniculum vulgare Mill.
Family
Umbelliferae (Apiaceae)
Macroscopy
Fruit is a cremocarp and usually splits into two mericarps.
The fruit is generally greenish to yellowish-brown.
It is elongated and slightly curved.
The apex has a bifid stylopod (split structure at the top of the fruit).
A carpophore is present in the centre.
The fruit has a sweet, aromatic odour and taste.
Microscopy
Anomocytic stomata are present on the epidermis of the pericarp.
The mesocarp contains lignified, reticulate parenchyma.
The inner epidermis of the pericarp shows a characteristic parquetry or mosaic arrangement of cells.
Vittae are present as secretory canals containing volatile oil (तेल से भरी secretory canals).
Vittae are usually brownish.
The endosperm contains:
Fixed oil
Aleurone grains
Small rosette-shaped calcium oxalate crystals
Trichomes and starch grains are absent.
Chemical Constituents
Contains about 3–7% volatile oil.
Also contains approximately 20% protein and 20% fixed oil.
The chief constituents of the volatile oil are:
Anethole — about 50%
Fenchone — about 20%
Anethole is a phenolic ether and is mainly responsible for the sweet aroma and taste.
Fenchone is a ketone and contributes to the characteristic flavour.
Varieties
| Variety | Taste / Odour | Volatile Oil (%) | Fenchone (%) |
|---|---|---|---|
| Saxony | Aromatic | 4.76 | 22.00 |
| Russian / Rumanian | Camphoraceous | 4.50 | 18.00 |
| French / Roman (Sweet) | Sweet aromatic | 2.10 | Nil |
| Indian | Camphoraceous | 0.72 | 6.70 |
| Japanese | Very sweet | 2.70 | 10.20 |
Uses
Used as a carminative — helps relieve gas (गैस कम करने वाला).
Used as an aromatic stimulant.
Used as an expectorant — helps in removal of mucus (बलगम निकालने में सहायक).
Used as a flavouring agent in pharmaceutical preparations.
Traditionally used to support digestion.
CORIANDER
Biological Source
Coriander consists of the dried ripe fruits of Coriandrum sativum Linn.
Family
Umbelliferae (Apiaceae)
Macroscopy and Microscopy
Fruit is nearly globular, about 3–5 mm in diameter.
It has 10 wavy primary ridges and 8 straight secondary ridges.
Vittae (oil canals) are present:
Four on the dorsal side
Two on the ventral side
The mesocarp contains a thick, wavy sclerenchymatous layer.
About five vascular bundles occur below each primary ridge.
The inner epidermis or endocarp consists of cells arranged in a characteristic parquetry pattern.
Chemical Constituents
Contains about 0.3–1% volatile oil.
The main constituent is d-linalool (coriandrol), which may form about 60–70% or more of the volatile oil depending on the source.
Linalool is responsible for the characteristic pleasant odour of ripe coriander fruits.
The unripe fruit and green plant may have an unpleasant mousy odour due mainly to aldehydes such as (E)-2-decenal and related compounds.
The unpleasant odour decreases during ripening as the characteristic coriander aroma develops.
Coriander leaves contain vitamins, including vitamin A precursors (carotenoids).
Uses
Used as an aromatic.
Used as a carminative — helps relieve gas (गैस कम करने वाला).
Used as a mild stimulant.
Used as a flavouring agent in pharmaceutical preparations and food.
Traditionally used to support digestion.
5. TANNINS
Definition
Tannins are complex, non-nitrogenous, polyphenolic secondary metabolites with relatively high molecular weight.
They have the ability to precipitate proteins and alkaloids.
They can also convert animal hide into leather, a process called tanning.
Tannins produce an astringent effect — they cause slight contraction of tissues (सिकुड़न पैदा करने वाला प्रभाव).
Classification of Tannins
| Class | Nature | Example |
|---|---|---|
| Hydrolysable Tannins | Esters of gallic or ellagic acid with a sugar core. They can be broken down by acids or enzymes. | Tannic acid, Chinese/Turkish galls |
| Condensed Tannins | Polymers mainly formed from flavan-3-ol units such as catechin. They are not easily hydrolysed. | Catechu, Cinchona bark, Kino |
Hydrolysable Tannins
They are mainly esters of gallic acid or ellagic acid with sugars.
On hydrolysis, they produce gallic acid or ellagic acid and sugar.
They are also called pyrogallol tannins.
Condensed Tannins
They are mainly formed from flavan-3-ol units, such as catechin.
They are also called catechol tannins or phlobatannins.
They are not easily hydrolysed.
On heating with mineral acids, they form red, insoluble phlobaphenes.
General Properties
Usually have an astringent taste.
Generally soluble in water and alcohol.
Generally insoluble in most non-polar organic solvents.
Give a blue-black or green-black colour with ferric chloride.
Precipitate proteins, gelatin and alkaloids.
Their protein-precipitating property is responsible for their use in tanning leather.
Their ability to precipitate alkaloids has historical importance in the treatment of some cases of alkaloidal poisoning, although this is not a recommended modern treatment.
CATECHU
Synonyms
Black Catechu; Cutch; Khair
Biological Source
Catechu is the dried aqueous extract obtained mainly from the heartwood of Acacia catechu Willd.
Family
Fabaceae (Leguminosae), sub-family Mimosoideae
Geographical Source
It is widely distributed in India and is also found in Myanmar and Nepal.
Preparation
The heartwood is cut into small chips.
The chips are boiled with water.
The liquid extract is concentrated by evaporation.
On cooling, a solid mass of catechu is obtained.
Macroscopy
Colour: Blackish-brown.
Appearance: Usually occurs as hard, brittle pieces.
Fracture: Brittle with a shiny surface.
Taste: Astringent followed by a slightly sweet after-taste.
Chemical Constituents
Catechin is an important condensed tannin and a major astringent constituent.
Epicatechin is also present.
Other constituents include:
Catechu-tannic acid
Quercetin
Gum
Epigallocatechin
Protocatechuic acid
On heating with mineral acid, catechin undergoes condensation and forms catechu red, an insoluble red pigment called a phlobaphene.
Chemical Test
Ferric Chloride Test
Procedure: Add ferric chloride solution to an aqueous solution of catechu.
Result: A dark green to greenish-black colour develops.
Indication: Presence of condensed tannins.
Uses
Used as a strong astringent — helps reduce excessive secretion and tissue irritation (सिकुड़न और स्राव कम करने वाला).
Used traditionally in preparations for diarrhoea.
Used in gargles and lozenges for sore throat and mouth irritation.
Used in tanning of leather.
Used in dyeing, particularly for producing khaki and brown shades.
Traditionally used as a masticatory in betel preparations.
Used in some tooth powders because of its astringent properties.
PTEROCARPUS (KINO)
Synonyms
Malabar Kino; Indian Kino; Bijasal; Vijayasar
Biological Source
Kino is the dried gummy exudate obtained by making incisions in the stem bark of Pterocarpus marsupium Roxb.
Family
Fabaceae (Leguminosae)
Geographical Source
It is found in the hilly and forest regions of India, including parts of:
Madhya Pradesh
Gujarat
Bihar
Karnataka
Kerala
West Bengal
Macroscopy
Occurs as small, angular and brittle fragments.
Colour: Dark red to blackish-red.
Surface is usually shiny.
Fracture: Brittle.
Taste: Strongly astringent.
Chemical Constituents
Contains a high proportion of kinotannic acid, an important tannin.
Other constituents include:
Kino-red
Catechol (pyrocatechin)
Resin
Gallic acid
Kino-red is a red phlobaphene formed by oxidation and other changes in kino constituents.
The heartwood also contains several flavonoids and polyphenols, including:
Pterostilbene
Epicatechin
Marsupin
Pterosupin
Uses
Used as a strong astringent.
Traditionally used in preparations for chronic diarrhoea.
Used traditionally to help reduce minor bleeding because of its astringent action.
The heartwood preparation known as Vijayasar has been traditionally used for diabetes and has been investigated for blood-glucose-lowering activity.
6. RESINS
Resins are amorphous, solid or semi-solid plant products made up of complex mixtures of different organic compounds.
They may contain resin acids, resin alcohols, resin esters, volatile oils and their oxidation products.
They are commonly produced as plant secretions or exudates (पौधे से निकलने वाला पदार्थ).
Some resins are formed in special resin ducts or cavities of plants.
Physical Properties
Usually hard or semi-solid at room temperature.
May be transparent or translucent.
Generally soften and melt on heating.
Insoluble in water.
Generally soluble in alcohol, chloroform, ether and other organic solvents.
Many resins have a characteristic odour due to the presence of volatile oil.
Classification of Resins Based on Chemical Nature
| Type | Chief Components | Examples |
|---|---|---|
| Acid Resins | Free resin acids | Colophony — abietic acid; Myrrh — resin acids |
| Ester Resins | Resin esters | Benzoin — coniferyl benzoate; Storax — cinnamyl cinnamate |
| Resin Alcohols | Resin alcohols or resinols | Guaiacum — guaiac resin alcohols |
| Oleoresins | Resin + volatile oil | Ginger, Capsicum, Turpentine |
| Gum-resins | Resin + gum, often with volatile oil | Myrrh, Asafoetida, Guggul |
1. Acid Resins
Mainly contain free resin acids.
Examples: Colophony and Myrrh.
2. Ester Resins
Contain esters of resin acids or resin alcohols.
Examples: Benzoin and Storax.
3. Resin Alcohols
Contain resin alcohols, also called resinols.
Example: Guaiacum.
4. Oleoresins
Natural mixtures of resin and volatile oil.
Examples: Ginger, Capsicum and Turpentine.
5. Gum-resins
Contain resin and gum, and may also contain volatile oil.
Examples: Myrrh, Asafoetida and Guggul.
BENZOIN
Synonyms
Gum Benzoin; Gum Benjamin; Loban
Biological Source
Benzoin is a balsamic resin obtained by making incisions in the stem bark of Styrax species.
Sumatra Benzoin: Obtained mainly from Styrax benzoin and related species.
Siam Benzoin: Obtained mainly from Styrax tonkinensis.
Family
Styracaceae
Geographical Source
Sumatra Benzoin: Mainly obtained from Sumatra and Java.
Siam Benzoin: Mainly obtained from Thailand, Laos and Vietnam.
Macroscopy
Sumatra Benzoin
Occurs as a greyish-brown mass containing whitish or pale tears.
Tears may have an almond-like appearance.
Odour is pleasant, balsamic and slightly vanilla-like.
Siam Benzoin
Occurs mainly as yellowish or pale tears.
Tears are relatively friable.
Has a pleasant vanilla-like odour.
Chemical Constituents
Contains benzoic acid and cinnamic acid and their esters.
Siam Benzoin: Richer in benzoic acid and its esters.
Sumatra Benzoin: Contains a higher proportion of cinnamic acid and its esters.
Vanillin is present and contributes to the pleasant aroma.
Also contains triterpenoid compounds.
Chemical Tests
1. Sublimation Test
Procedure: Heat powdered benzoin carefully.
Result: Characteristic needle-shaped crystals of benzoic acid are obtained.
Indication: Presence of benzoic acid.
2. Alkali Test
Procedure: Warm benzoin with alcoholic potassium hydroxide (KOH) and then acidify the solution.
Result: The characteristic odour of benzoic/cinnamic acid may be noticed.
Uses
Used as an expectorant — helps remove mucus (बलगम निकालने में सहायक).
Used as a mild antiseptic.
Used as a carminative.
Used as an aromatic stimulant.
Used in perfumery and cosmetic preparations.
Used in Compound Benzoin Tincture (Friar's Balsam) for application to minor skin cracks and wounds.
Used as a preservative to delay rancidity of fats and oils.
Used in incense.
GUGGUL
Synonyms
Gum Guggul; Indian Bdellium; Salai-guggul
Biological Source
Guggul is the oleo-gum-resin obtained by making incisions in the bark of Commiphora wightii.
Commiphora mukul is an older name used for this plant.
Family
Burseraceae
Geographical Source
Guggul is mainly obtained from the dry regions of Rajasthan, Gujarat and Madhya Pradesh in India.
Macroscopy
Occurs as irregular tears or agglomerated masses.
Colour ranges from golden-yellow to brown.
It may be viscid (sticky) when fresh.
Odour is aromatic and characteristic.
Taste is bitter and slightly acrid.
Chemical Constituents
Guggulsterones E and Z are important active constituents.
They are steroidal ketones and have been studied for their effects on lipid metabolism.
Contains about 30% resin.
Contains about 20% gum.
Contains about 8% volatile oil.
Volatile oil contains myrcene and other terpenes.
Uses
Traditionally used for high blood lipid levels (hyperlipidaemia).
Guggulsterones have been studied for their effects on cholesterol and triglyceride metabolism.
Traditionally used as an anti-inflammatory and for joint complaints.
Used in traditional preparations for rheumatic conditions.
GINGER
Synonyms
Adrak — Fresh Ginger; Sunthi — Dried Ginger
Biological Source
Ginger consists of the dried rhizome of Zingiber officinale Roscoe.
Family
Zingiberaceae
Geographical Source
Major sources include India, China, Jamaica and Nigeria.
Macroscopy
Rhizome is laterally flattened and branched.
It has a characteristic hand-shaped appearance.
Colour is buff to yellowish-brown.
Odour is strong and aromatic.
Taste is pungent and warm.
Chemical Constituents
Contains oleoresin, which contains both volatile oil and pungent constituents.
The volatile oil contains:
Zingiberene
Zingiberol
Other terpenes
Important pungent constituents are gingerols.
Gingerols are major pungent constituents of fresh ginger.
During drying or storage, gingerols can convert into shogaols, which are generally more pungent.
Zingerone is another important constituent formed during processing.
Uses
Used as a carminative — helps relieve gas (गैस कम करने वाला).
Used as a stomachic — supports digestion (पाचन में सहायक).
Used as an antiemetic — helps reduce nausea and vomiting (मतली और उल्टी कम करने वाला).
Commonly used for motion sickness.
Used as a flavouring agent in foods and beverages.
Ginger and its constituents have also been studied for anti-inflammatory effects.
ASAFOETIDA
Synonym
Hing
Biological Source
Asafoetida is the oleo-gum-resin obtained by making incisions in the living rhizome and roots of Ferula asafoetida and related Ferula species.
Family
Umbelliferae (Apiaceae)
Geographical Source
It is mainly obtained from Afghanistan and Iran. It is also cultivated or collected in some parts of India, including Kashmir and Punjab.
Macroscopy
Occurs as irregular tears or masses.
Fresh material is greyish-white.
On exposure to air, it changes through pinkish to reddish-brown.
Odour is very strong, persistent and alliaceous (garlic-like).
Taste is bitter and acrid.
Chemical Constituents
Resin: About 40–65%.
Resin contains ferulic acid esters and asaresinotannols.
Gum: About 20–25%.
Volatile oil: About 4–20%.
The volatile oil contains sulphur-containing compounds, mainly disulphides, which are responsible for the strong characteristic odour.
Uses
Used as a carminative — helps relieve intestinal gas (आंतों की गैस कम करने वाला).
Traditionally used for flatulence and digestive discomfort.
Used as a flavouring agent in curries, sauces and pickles.
Also used in some traditional veterinary preparations.
MYRRH
Synonym
Gum Myrrh
Biological Source
Myrrh is the oleo-gum-resin obtained from the stem of Commiphora myrrha.
Commiphora molmol is an older name used for this plant.
Family
Burseraceae
Geographical Source
Myrrh is mainly obtained from Somalia, Ethiopia and Saudi Arabia.
Macroscopy
Occurs as irregular tears or agglutinated masses.
Colour ranges from reddish-brown to yellowish-brown.
Fracture is often oily or resinous.
Odour is aromatic and balsamic.
Taste is bitter, acrid and aromatic.
Chemical Constituents
Resin: About 25–40%.
Contains resin acids such as commiphoric acid and commiphorinic acid.
Gum: About 57–61%.
Volatile oil: About 8%.
Volatile oil contains constituents such as heerabolene and eugenol.
Uses
Used as an astringent — causes mild tissue contraction (सिकुड़न पैदा करने वाला).
Used as an antiseptic in some topical preparations.
Traditionally used in mouthwashes and gargles for gum problems and mouth ulcers.
Used in some dental preparations.
Used as an aromatic and carminative.
Also used in incense and perfumery.
COLOPHONY
Synonyms
Rosin; Colophony Resin
Biological Source
Colophony is the solid residue left after removal of volatile oil (oil of turpentine) from the oleoresin of Pinus species, including Pinus palustris.
Family
Pinaceae
Geographical Source
Major sources include:
Southern United States
France
India, particularly the Himalayan chir-pine regions
Macroscopy
Occurs as hard, brittle and glassy lumps.
May be transparent to translucent.
Colour ranges from pale yellow to amber-brown.
Odour: Faint, characteristic terebinthinate odour.
Fracture: Brittle.
Chemical Constituents
Mainly contains abietic acid, an important resin acid.
Other resin acids include:
Pimaric acid
Neoabietic acid
Small amounts of other resinous substances may also be present.
Chemical Test
Copper Acetate Test
Procedure: Shake powdered colophony with petroleum ether and dilute copper acetate solution.
Result: The petroleum ether layer develops an emerald-green colour.
Indication: This characteristic colour reaction supports the identification of colophony.
Uses
Used as a stiffening agent in ointments, plasters, adhesive tapes and cerates.
Used in surgical and court plasters.
Used industrially in:
Varnishes
Printing inks
Soaps
Sealing wax
Wood polishes
Also has applications in adhesives and coatings.
7. GLYCOSIDES
Definition
Glycosides are organic compounds obtained from plant or animal sources.
On acid or enzymatic hydrolysis, they give:
One or more sugar parts → Glycone
Non-sugar part → Aglycone or Genin
Hydrolysis means breaking a compound into simpler parts using water, acid or an enzyme (यौगिक को छोटे भागों में तोड़ना).
The aglycone is mainly responsible for the chemical and therapeutic activity.
The glycone can influence the solubility, absorption and transport of the aglycone.
Chemically, many glycosides are acetals formed by linkage between the sugar and aglycone.
The sugar may be linked to the aglycone through O, C, S or N.
Most naturally occurring glycosides have a β-linkage.
Common sugars include glucose, galactose, mannose, rhamnose, digitoxose and cymarose.
Properties
Most glycosides are colourless and crystalline solids.
Anthraquinone glycosides may be red or orange.
Flavonoid glycosides are often yellow.
Many glycosides are soluble in water and alcohol.
They are generally insoluble in chloroform and ether.
Glycosides can be extracted using suitable extraction methods, including the Stas–Otto method.
Classification Based on Glycosidic Linkage
| Type | Linkage | Examples |
|---|---|---|
| C-Glycoside | Sugar is directly linked to a carbon atom of the aglycone | Aloe, Cascara, Cochineal |
| O-Glycoside | Sugar is linked through an oxygen atom | Senna, Rhubarb |
| S-Glycoside | Sugar is linked through sulphur | Sinigrin in Black Mustard |
| N-Glycoside | Sugar is linked through nitrogen | Nucleosides |
SENNA
Synonyms
Indian Senna; Tinnevelly Senna; Alexandrian Senna
Biological Source
Senna consists of the dried leaflets and pods of:
Cassia angustifolia — Indian/Tinnevelly Senna
Cassia acutifolia — Alexandrian Senna
Modern botanical classification places these mainly under Senna alexandrina.
Family
Leguminosae (Fabaceae)
Macroscopy and Microscopy
Senna leaf is isobilateral — both sides have a similar internal arrangement (दोनों सतहों की बनावट लगभग समान).
The active constituents are mainly present in the epidermal tissues of the leaflets and pericarp of the pods.
Epidermal cells are polygonal with straight anticlinal walls.
Paracytic stomata are present on both surfaces.
Mucilage deposits may occur in epidermal cells.
Non-glandular hairs are unicellular, thick-walled and warty.
A single palisade layer is present on both sides of the leaf.
Spongy tissue contains idioblasts with cluster crystals of calcium oxalate.
The midrib contains a crescent-shaped vascular bundle.
Lignified pericyclic fibres occur around the vascular bundle and are associated with prismatic calcium oxalate crystals.
Chemical Constituents
The main active constituents are anthraquinone glycosides, particularly:
Sennoside A
Sennoside B
Sennoside C
Sennoside D
Other constituents include:
Rhein
Emodin
Aloe-emodin
Chrysophanol
Senna also contains naphthalene glycosides.
Kaempferol, a flavonoid, contributes to the yellow colour.
Sennosides A and B are the major active constituents.
Sennosides are dianthrone glycosides — glycosides formed from two anthrone units.
Sennidin is the aglycone part obtained after removal of the sugar.
Alexandrian Senna generally contains a higher amount of sennosides than Indian Senna.
Adulterants / Substitutes
1. Dog Senna — Cassia obovata
Leaves are obovate in shape.
Lower epidermis has papillose cells.
2. Arabian Senna
Obtained from wild forms of Cassia angustifolia.
3. Palthe Senna — Cassia auriculata
Characteristically lacks anthraquinone glycosides.
Chemical Test
Borntrager's Test
Procedure:
Powder the drug and extract it with a suitable solvent.
Add alcoholic potassium hydroxide (KOH) and heat.
Dilute and filter the extract.
Acidify with hydrochloric acid (HCl).
Extract with ether or benzene.
Separate the organic layer and add dilute ammonia solution.
Result: The ammoniacal layer becomes pink to red.
Indication: Indicates the presence of anthraquinone derivatives.
Uses
Senna is a stimulant laxative — increases bowel movement and helps relieve constipation (कब्ज दूर करने वाला).
Used mainly for short-term treatment of constipation.
It is also used for bowel evacuation before certain medical procedures.
ALOE
Synonyms
Ghritkumari; Musabbar
Biological Source
Aloe consists of the dried juice (latex) obtained from the leaves of various Aloe species.
Family
Asphodelaceae
Older pharmacognosy texts may mention Liliaceae.
Species and Commercial Varieties
| Species | Commercial Variety |
|---|---|
| Aloe barbadensis | Curacao Aloe |
| Aloe ferox, Aloe spicata | Cape Aloe |
| Aloe perryi | Socotrine Aloe |
| Aloe vera | Indian Aloe |
Macroscopy — Different Varieties
| Variety | Form | Colour | Fracture |
|---|---|---|---|
| Curacao Aloe | Opaque masses | Yellow-brown to chocolate-brown | Waxy |
| Cape Aloe | Transparent and glassy | Dark brown to greenish-brown | Smooth and glassy |
| Socotrine Aloe | Opaque | Reddish-black to brownish-black | Conchoidal |
| Zanzibar Aloe | Opaque | Liver-brown | Smooth and even |
Microscopy
Epidermis is strongly cuticularised and has stomata on both surfaces.
Needle-shaped calcium oxalate crystals may be present in the parenchyma.
Vascular bundles occur in two rows at the junction of the two leaf regions.
An endodermal/pericyclic region is present around the vascular bundles.
Aloe gel is present in the mucilaginous parenchyma cells.
The bitter aloe latex/juice is associated with the tissues near the vascular bundles.
Chemical Constituents
The chief active constituents are anthraquinone-related glycosides, mainly aloin.
Aloin consists mainly of barbaloin and related C-glycoside forms.
Barbaloin is an aloe-emodin anthrone C-10 glucoside.
Other constituents include aloesin and resinous substances.
Aloe latex contains compounds responsible for its laxative action.
Chemical Tests
1. Schoenteten's / Borax Test
Procedure: Boil the powdered aloe with water and filter the solution. Perform the borax test.
Result: Green fluorescence is observed.
2. Bromine Test
Procedure: Add bromine solution to the suitable aloe extract.
Result: A pale-yellow precipitate is formed.
3. Modified Borntrager's Test
Procedure: Treat the aqueous aloe extract with ferric chloride and hydrochloric acid, heat for hydrolysis and extract with an organic solvent. Shake the organic layer with ammonia.
Result: The ammoniacal layer shows a rose-pink to cherry-red colour.
Indication: Indicates anthraquinone derivatives, including aloe-emodin-related compounds.
Adulterants / Substitutes
Natal Aloe
Resembles Cape Aloe microscopically.
Has a weaker purgative action.
Mocha Aloe
Usually brittle, black and glassy.
Has a strong characteristic odour.
Uses
Aloe latex is used as a stimulant laxative for constipation.
Aloe preparations are also used in topical products for skin moisturisation and soothing.
Important: Aloe latex and aloe gel are different materials. The latex contains laxative anthraquinone derivatives, whereas the inner leaf gel is mainly used in topical preparations.
Oral use of aloe latex should be limited because excessive use can cause abdominal cramps, diarrhoea and electrolyte imbalance.
BITTER ALMOND
Synonym
Amygdala Amara; Bitter Almond; Badam
Biological Source
Bitter Almond consists of the dried ripe seeds of Prunus dulcis (formerly Prunus amygdalus) var. amara.
Sweet almond, Prunus dulcis var. dulcis, is used as a comparison.
Family
Rosaceae
Chemical Constituents
The chief active constituent is the cyanogenic glycoside amygdalin, present in bitter almonds.
Amygdalin is a cyanogenic glycoside — a compound that can release toxic hydrogen cyanide (जहरीली HCN गैस छोड़ने वाला यौगिक).
On enzymatic hydrolysis by emulsin, amygdalin produces:
Amygdalin → Benzaldehyde + Hydrocyanic acid (HCN) + 2 Glucose
Benzaldehyde is responsible for the characteristic almond-like odour.
Uses
Historically used in some traditional preparations as a flavouring and mild soothing agent.
Bitter almond preparations have also been used in external skin preparations.
Important Safety Note: Bitter almonds can release hydrocyanic acid (HCN), which is highly toxic. Therefore, raw bitter almonds should not be consumed in quantity, and they should not be used for self-medication.
8. IRIDOIDS, OTHER TERPENOIDS AND NAPHTHOQUINONES
IRIDOIDS
Iridoids are a group of monoterpenoids commonly found in medicinal plants.
They have a characteristic cyclopentanoid monoterpene structure.
They are biosynthesized from 8-oxogeranial.
Most iridoids occur as glycosides, usually linked with glucose.
Important examples include gentiopicroside, aucubin and catalpol.
Iridoids mainly help plants in defence against herbivores and microorganisms.
Important Point
Iridoid glycoside = Iridoid part + Sugar part
NAPHTHOQUINONES
Naphthoquinones are organic compounds structurally related to naphthalene.
The two important structural forms are:
1,2-Naphthoquinone
1,4-Naphthoquinone
Important natural examples include lawsone, juglone and plumbagin.
They are generally present as free compounds rather than glycosides.
Many naphthoquinones show antimicrobial and cytotoxic activities, depending on their structure.
Some naphthoquinones can produce reactive oxygen species (ROS), which may damage cells.
Naphthoquinones occur in plants belonging to different plant families.
GENTIAN
Synonym
Gentian Root; Radix Gentianae
Biological Source
Gentian consists of the dried rhizomes and roots of Gentiana lutea Linn.
Family
Gentianaceae
Macroscopy
Rhizome is yellowish-brown and shows transverse rings or annulations.
Conical buds may be present at the upper end.
Roots are narrower and continuous with the rhizome.
Roots show longitudinal wrinkles and rootlet scars.
Odour: Characteristic.
Taste: Initially slightly sweet, followed by a very bitter taste.
Microscopy
Rhizome
Transverse section shows cork, cortex, cambium, phloem, xylem and pith.
Cork cells are thin-walled.
Cortical parenchyma may contain oil droplets and calcium oxalate.
Phloem occurs in small groups.
Phloem fibres are absent.
Xylem contains spiral and annular vessels.
Interxylary phloem may be present.
Root
Pith is absent in the root.
The primary xylem is usually triarch (having three main xylem groups).
Chemical Constituents
The important bitter glycosides are:
Gentiopicroside (Gentiopicrin)
Amarogentin
Gentiopicroside is water-soluble and crystalline.
During processing, gentiopicroside may undergo hydrolysis:
Gentiopicroside + Water → Gentiogenin + Glucose
Chemical Test
Fluorescence Test
Procedure: Prepare an extract of the drug and observe it under UV light.
Result: A light-blue fluorescence may be observed.
Uses
Used as a bitter tonic — a bitter drug that stimulates appetite and digestion (भूख और पाचन बढ़ाने में सहायक).
Traditionally used to improve appetite.
Used in preparations for loss of appetite and digestive discomfort.
ARTEMISIA
Synonym
Santonica; Worm Seeds
Biological Source
Santonica consists mainly of the dried, unexpanded flower heads of Artemisia cina Berg.
Other Artemisia species have also been used as sources of related drugs.
Family
Compositae (Asteraceae)
Microscopy
Leaves show an isobilateral arrangement.
Anomocytic stomata are present.
Glandular trichomes are present on both surfaces.
Glandular trichomes have a short stalk and multicellular head.
T-shaped covering trichomes are an important diagnostic feature.
Chemical Constituents
Contains about 1–2% volatile oil.
The chief active constituent of santonica is santonin, a sesquiterpene lactone.
Other constituents include:
Cineole
Pinene
Resinous substances
Artemisinin is a different sesquiterpene lactone obtained mainly from Artemisia annua.
Artemisinin contains a characteristic endoperoxide linkage and is important in antimalarial therapy.
Santonin and artemisinin should not be confused with each other.
Identification Test
Procedure: Boil about 1 g of powdered drug with 10 mL alcohol and filter. Add sodium hydroxide solution to the filtrate and heat.
Result: A red colour develops.
Indication: Supports the identification of santonin-containing drug.
Uses
Santonica was traditionally used as an anthelmintic — a drug used against intestinal worms (कीड़ों के विरुद्ध उपयोगी).
Santonin was particularly used against roundworms.
Its use has largely been replaced by safer modern anthelmintic drugs.
TAXUS
Synonyms
Yew; Himalayan Yew
Biological Source
Taxus drugs are obtained from different parts of Taxus species, especially the leaves and bark.
For the Himalayan species, Taxus wallichiana is an important source.
Family
Taxaceae
Important Species and Parts Used
| Species | Common Name | Important Part Used |
|---|---|---|
| Taxus baccata | English/European Yew | Mainly leaves |
| Taxus brevifolia | Pacific Yew | Stem bark |
| Taxus canadensis | Canadian Yew | Leaves and roots |
| Taxus cuspidata | Japanese Yew | Leaves |
| Taxus wallichiana | Himalayan Yew | Leaves and bark |
Chemical Constituents
The important group of constituents is taxane diterpenoids.
Paclitaxel (Taxol) is an important taxane obtained from Taxus species.
Other important taxanes include:
Cephalomannine
10-Deacetylbaccatin III
Docetaxel is a semi-synthetic taxane derivative used as an anticancer drug.
Mechanism of Action of Paclitaxel
Paclitaxel binds to tubulin and stabilizes microtubules.
It prevents the normal breakdown of microtubules during cell division.
This causes arrest of cell division and ultimately leads to death of susceptible cancer cells.
Therefore, paclitaxel is an important anticancer drug.
Uses
Paclitaxel is used in the treatment of several cancers, including:
Ovarian cancer
Breast cancer
Non-small-cell lung cancer
Other selected cancers
Important: Different parts of yew contain toxic compounds. Crude yew material should not be used for self-medication.
CAROTENOIDS
Chemical Class
Tetraterpenoids (C₄₀ compounds)
Biological Source
Carotenoids are natural pigments widely present in:
Fruits
Vegetables
Green plants
Algae
Some fungi and bacteria
They are responsible for the yellow, orange and red colours of many plants.
Biosynthesis and Chemistry
Carotenoids are C₄₀ tetraterpenoid compounds.
They are formed biosynthetically from two C₂₀ units derived from geranylgeranyl pyrophosphate.
They contain a long chain of conjugated double bonds.
These double bonds are responsible for their colour and sensitivity to light and oxidation.
Important Carotenoids
α-Carotene
β-Carotene
Lutein
Zeaxanthin
Lycopene
Properties
Carotenoids are generally yellow, orange or red pigments.
They are fat-soluble and poorly soluble in water.
They are sensitive to light, heat and oxidation.
In plants, they act as accessory pigments in photosynthesis.
Some carotenoids, especially β-carotene, can be converted into vitamin A in the body.
Many carotenoids have antioxidant properties.
General Extraction
Extract the plant material with a suitable solvent such as acetone.
Filter the extract.
Repeat extraction until the plant material becomes nearly colourless.
Combine the extracts.
Transfer the pigments into a suitable non-polar solvent such as diethyl ether or petroleum ether.
Remove the solvent carefully to obtain the carotenoid-rich extract.
Chemical Test
Sulphuric Acid Test
Procedure: Treat the carotenoid extract with chloroform (CHCl₃) and carefully add sulphuric acid (H₂SO₄).
Result: A blue colour at the interface may develop.
Indication: Supports the presence of carotenoid pigments.
Therapeutic and Biological Importance
β-Carotene acts as a provitamin A — it can be converted into vitamin A in the body (विटामिन A बनने में सहायक).
Vitamin A is important for normal vision, epithelial tissues and immune function.
Lutein and zeaxanthin are important carotenoids found in the eye.
Many carotenoids have antioxidant properties and help protect cells from oxidative damage.
Lycopene is an important dietary carotenoid found in foods such as tomatoes and watermelon.
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