Pharmacognosy and Phytochemistry BBO5T12

Syllabus topics (RTMNU)

• Pharmacognosy: Definition, scope and importance; History and development
• Sources of crude drugs: Plant origin, Animal origin, Mineral origin
• Classification of crude drugs: Alphabetical, Morphological, Chemical, Pharmacological
• Adulteration of crude drugs: Types and detection

Pharmacognosy — definition, scope and importance

Pharmacognosy (Greek pharmakon = drug, gnosis = knowledge) is the study of crude drugs of natural origin — plants, animals and minerals — their identification, cultivation, collection, preparation, chemistry, evaluation, preservation and uses. The term was used by J. A. Schmidt (1811) and C. A. Seydler (1815, Analectica Pharmacognostica). Phytochemistry is the chemistry of plant constituents.

Scope and importance: correct identification and standardisation of herbal drugs; detection of adulteration; discovery of new drugs (about a quarter of modern medicines come directly or indirectly from plants — morphine, quinine, digoxin, vincristine, artemisinin, taxol); raw material for pharmaceuticals, nutraceuticals, cosmetics, flavours; basis of Ayurveda, Unani and Siddha; conservation and cultivation of medicinal plants; trade and rural livelihoods.

History and development

• Ancient: Indian Rigveda and Atharvaveda; Charaka Samhita (medicine) and Sushruta Samhita (surgery) describe hundreds of plants; Egyptian Ebers Papyrus (about 1550 BC); Chinese emperor Shen Nung's herbal; Hippocrates (father of medicine).
• Classical: Dioscorides' De Materia Medica (1st century AD) — about 600 plants, used for 1,500 years; Galen — "galenical" preparations; Arab physicians (Avicenna).
• Modern: isolation of pure compounds — morphine from opium by Sertürner (early 1800s), quinine, atropine; pharmacopoeias; microscopy for drug identification; 20th century — chromatography, spectroscopy, biotechnology, tissue culture, molecular markers (DNA barcoding) for authentication; WHO support for traditional medicine; Ministry of AYUSH and National Medicinal Plants Board (2000) in India.

Sources of crude drugs

• Plant origin (most): roots (Rauvolfia, ashwagandha), rhizomes (ginger, turmeric), barks (cinnamon, cinchona), woods (sandalwood), leaves (senna, vasaka, digitalis), flowers (clove buds, saffron stigma), fruits (amla, fennel), seeds (isabgol, nux-vomica), whole plants (kalmegh), and unorganised products (gums, resins, latex, oils).
• Animal origin: honey, beeswax, lanolin (wool fat), cod-liver oil, shellac (lac insect), musk, gelatin, insulin and heparin (earlier from animals), cantharides.
• Mineral origin: kaolin, talc, bentonite, chalk, calamine, iron and other minerals and bhasmas used in Ayurveda, shilajit (mineral pitch), paraffin.
• Also microbes (antibiotics) and marine organisms.

Classification of crude drugs

Adulteration of crude drugs — types and detection

Adulteration is the substitution of the original crude drug, partly or wholly, with other similar-looking material, or addition of inferior/foreign substances, so the drug does not meet quality standards. It may be deliberate (for profit) or accidental (confusion of names, careless collection).

Types:

1. Substitution with inferior commercial varieties — e.g. Arabian senna (Cassia angustifolia wild) or Cassia auriculata for senna; Japanese ginger for Indian ginger.
2. Substitution with exhausted drug — material already extracted (e.g. exhausted clove, ginger, saffron) dried and sold again, sometimes coloured.
3. Substitution with superficially similar but cheap/worthless material — e.g. papaya seeds in black pepper, Curcuma zedoaria for turmeric.
4. Addition of artificially manufactured substitutes — artificial nutmeg, wax-coated paraffin.
5. Adulteration with synthetic chemicals — citral added to lemon oil, synthetic dyes (metanil yellow, lead chromate) in turmeric.
6. Use of harmful/inferior quality or vegetative parts — stalks, stones, sand added to increase weight; deteriorated (old, mouldy) drugs; spoiled during storage.

Detection (evaluation) methods:

• Organoleptic/morphological: colour, odour, taste, size, shape, texture, fracture (e.g. fibrous fracture of ginger).
• Microscopic: stomata, trichomes, crystals, starch grains, fibres; quantitative microscopy — stomatal index, palisade ratio, vein-islet number, lycopodium spore method.
• Physical: moisture content, ash values (total, acid-insoluble — shows sand/earth), extractive values, swelling index (isabgol), foaming index, melting point, refractive index, optical rotation, UV fluorescence.
• Chemical: colour reactions and assays of active constituents (e.g. Borntrager's test for anthraquinones, test for metanil yellow with HCl — violet/magenta colour), chromatographic fingerprints (TLC/HPTLC/HPLC).
• Biological: bioassays on animals/micro-organisms (e.g. digitalis potency).
• Molecular: DNA barcoding and markers for authentication.

Likely exam questions

1. (Long, 8 marks) Define pharmacognosy. Give its scope and history. Describe the sources of crude drugs.
2. (Long, 8 marks) What is adulteration? Describe its types and methods of detection.
3. (Short, 4 marks) Explain the morphological classification of crude drugs.
4. (Short, 4 marks) Write a note on the chemical classification of crude drugs.
5. (Short, 4 marks) Give two examples each of crude drugs of animal and mineral origin.

Syllabus topics (RTMNU)

• Pharmacognostic study of organised drugs (root, stem, leaf, flower, fruit, seed), unorganised drugs (gums, resins, latex): Morphological characters, Microscopic evaluation of crude drugs, Powder analysis
• Pharmacognostic study of selected medicinal plants: Curcuma longa, Zingiber officinale, Syzygium aromaticum, Cinnamomum verum, Senna alexandrina, Azadirachta indica and Plantago ovata

Pharmacognostic study of organised and unorganised drugs

Organised drugs have a cellular structure — roots, rhizomes, stems/barks, woods, leaves, flowers, fruits, seeds. Unorganised drugs have no cellular structure — gums (e.g. acacia, tragacanth, karaya), resins (colophony, benzoin, guggul), latex (opium, papain), dried juices (aloe), extracts, oils and waxes; they are evaluated mainly by physical and chemical tests.

(a) Morphological characters (macroscopy): shape, size, colour (outer and cut surface), surface markings (scars, wrinkles), fracture (short, fibrous, splintery), odour, taste, texture.

(b) Microscopic evaluation: transverse sections and surface preparations cleared with chloral hydrate and stained. Diagnostic features: types of stomata (anomocytic, anisocytic, diacytic, paracytic), trichomes (covering, glandular), calcium oxalate crystals (prisms, rosettes/clusters, raphides, sandy), starch grains (shape, hilum), fibres, sclereids, vessels, oil cells, secretory canals. Quantitative microscopy: stomatal number and stomatal index = S/(S + E) × 100, vein-islet and vein-termination numbers, palisade ratio — useful to distinguish closely related leaves (e.g. Indian and Alexandrian senna).

(c) Powder analysis: powdered drug is mounted in water, glycerine and chloral hydrate and treated with reagents: phloroglucinol + HCl (lignified cells pink-red), iodine (starch blue), Sudan III (oils/fats red), ruthenium red (mucilage pink), FeCl₃ (tannins blue-black), dilute HCl (calcium oxalate dissolves without effervescence; carbonate with effervescence); fluorescence under UV.

Pharmacognosy of selected medicinal plants

Key identification features and tests

• Turmeric: ovate primary ("bulbs") and cylindrical lateral rhizomes ("fingers"), deep yellow-orange inside, horny fracture; microscopy — parenchyma with gelatinised starch and yellow oil cells. Test: powder + conc. H₂SO₄ → crimson colour; turmeric paper + boric acid → reddish-brown, turning greenish-black with alkali.
• Ginger: laterally compressed, branched "hands", buff colour, fibrous fracture, aromatic pungent taste; microscopy — oleoresin cells, starch grains (flat, oval with eccentric hilum), septate fibres.
• Clove: nail-shaped bud — cylindrical hypanthium with 4 sepals and a dome of 4 unopened petals; oil glands (schizolysigenous) in hypanthium, calcium oxalate clusters, no starch, no sclereids (stalks contain sclereids — adulterant). Good clove sinks in water/exudes oil on pressing. Test: oil/ section + 50% KOH → needle crystals of potassium eugenate; FeCl₃ → blue (phenolic eugenol).
• Cinnamon: quills of thin bark (about 0.5 mm) packed one inside another, yellowish-brown, splintery fracture, sweet aromatic taste; microscopy — pericyclic sclerenchyma ring, phloem fibres, oil cells, mucilage cells, starch, small acicular calcium oxalate crystals, no cork.
• Senna: lanceolate leaflets with unequal (asymmetric) base, greyish-green; isobilateral leaf, paracytic stomata, unicellular warty trichomes, calcium oxalate prisms and clusters. Borntrager's test: boil with dilute H₂SO₄, extract with benzene/chloroform, add ammonia → pink to red ammoniacal layer (anthraquinones).
• Neem leaf: imparipinnate compound leaf with falcate, serrate leaflets with oblique base; dorsiventral, anomocytic stomata; extremely bitter taste.
• Isabgol: boat-shaped, pinkish-grey seeds about 2–3 mm, hilum on concave side, no odour, bland mucilaginous taste; epidermal cells full of mucilage that swells in water (high swelling factor, about 10–14 ml per g for seeds and much higher for husk); test with ruthenium red → pink mucilage.

Likely exam questions

1. (Long, 8 marks) Describe the biological source, macroscopic and microscopic characters, chemical constituents and uses of senna.
2. (Long, 8 marks) Give the pharmacognosy of clove and cinnamon.
3. (Short, 4 marks) What is powder analysis of crude drugs? Name the reagents used.
4. (Short, 4 marks) Write the biological source, constituents and uses of isabgol.
5. (Short, 4 marks) Distinguish between organised and unorganised drugs with examples.

Syllabus topics (RTMNU)

• Cultivation practices and post-harvest processing of Curcuma longa, Zingiber officinale, Syzygium aromaticum and Cinnamomum verum
• Indian trade in medicinal and aromatic plants: plants and phytochemicals exported from India; imported into India (including adaptogens and allied materials); endangered medicinal plants; medicinal plants prohibited to export from India
• Quality control of herbal drugs
• WHO guidelines for use of herbal medicines

Cultivation and post-harvest processing

Turmeric (Curcuma longa)

• Climate and soil: warm humid tropics, 20–30 °C, rainfall about 1,500 mm or irrigation; well-drained sandy/clay loam rich in organic matter, pH 5–7.5; cannot tolerate waterlogging.
• Propagation and planting: mother and finger rhizomes (about 2,000–2,500 kg/ha) planted in April–June on raised beds or ridges about 45 × 25 cm; heavy FYM; mulching with green leaves; weeding and earthing up. Varieties: Rajapuri (Maharashtra), Salem, Erode, Alleppey (high curcumin), Lakadong (Meghalaya), Pratibha.
• Harvest: 7–9 months after planting (January–March) when leaves turn yellow and dry; rhizomes dug out; fingers and mothers separated.
• Curing: rhizomes boiled in water (sometimes with a little lime/sodium bicarbonate) for about 45–60 minutes until soft and aromatic — gelatinises starch and gives uniform colour.
• Drying: sun-dried for 10–15 days on mats to about 8–10% moisture (dry recovery about 20–30%).
• Polishing: rough surface removed by rubbing in hand-operated or power drums; colouring with turmeric powder may be done; grading into fingers, bulbs and splits. Maharashtra (Sangli market), Telangana, Tamil Nadu (Erode) are major producers.

Ginger (Zingiber officinale)

• Climate and soil: warm humid climate, rainfall 1,500–3,000 mm; well-drained loam; partial shade tolerated.
• Planting: seed rhizome bits (2.5–5 cm, about 1,500–1,800 kg/ha) in April–May on raised beds, 20–25 cm spacing; mulching; manuring; shade/intercropping; control of soft rot.
• Harvest: about 6 months for fresh (vegetable) ginger; 8–9 months, when leaves dry, for dry ginger.
• Processing: rhizomes soaked overnight, washed, outer skin scraped with bamboo splinters (not steel, which darkens it), sun-dried 8–10 days → unbleached/scraped ginger (e.g. Cochin and Calicut ginger); bleached ginger is treated with lime; dry recovery about 16–25%. Also preserved ginger, ginger oil and oleoresin. Kerala, Karnataka, Meghalaya, Assam are major producers.

Clove (Syzygium aromaticum)

• Climate and soil: evergreen tree of humid tropics, rainfall 1,500–2,500 mm, up to about 900 m elevation; deep, rich, well-drained loam; Kerala, Tamil Nadu (Nilgiris, Kanyakumari), Karnataka hills. World leaders: Indonesia, Madagascar, Tanzania (Zanzibar).
• Propagation: fresh seeds (lose viability quickly) sown in nursery; 18–24-month seedlings planted about 6–7 m apart with partial shade when young; mulching, irrigation in summer.
• Flowering and harvest: starts bearing after about 6–8 years; buds harvested when full-grown and turning from green to pink, before opening — by hand from ladders, without breaking branches.
• Processing: buds separated from stalks and sun-dried for 4–5 days until dark brown and brittle (moisture about 10–12%); dry recovery about 30–35%; good clove is plump, oily and sinks in water. Stalks and leaves are distilled for oil.

Cinnamon (Cinnamomum verum)

• Climate and soil: warm humid tropics, rainfall 1,500–2,500 mm, sandy loam to laterite soils; Sri Lanka is the main producer of true cinnamon; in India — Kerala, Karnataka, Tamil Nadu.
• Propagation: seeds or rooted cuttings/air layers; planted about 3 × 3 m (or closer).
• Coppicing and harvest: plants cut back at 2–3 years; shoots from the stump are harvested every 2 years, in the rainy season (when bark peels easily) when shoots are 1.5–2 m long and bark turns brown.
• Processing: shoots cut into pieces, bark is slit and peeled, kept overnight to ferment slightly, the outer bark and cork scraped off; inner bark pieces are placed one inside another to form compound quills about 1 m long and dried in shade for 4–5 days, then sun. Grades: quills, quillings (broken), featherings, chips. Leaf and bark oils by steam distillation.

Indian trade in medicinal and aromatic plants

India is among the world's largest producers and exporters of medicinal and aromatic plants (MAPs) and herbal products. Trade figures change every year — check latest data (e.g. from Pharmexcil, Spices Board, NMPB).

• (a) Exported from India (with phytochemicals): isabgol husk (psyllium — India is the main world supplier), senna leaves and pods (sennosides), turmeric (curcumin), ginger, spices and spice oleoresins, ashwagandha (withanolides), mint oil and menthol (India is a leading producer), lemongrass, palmarosa, citronella and vetiver oils, Gloriosa superba seeds (colchicine), neem products (azadirachtin), amla, guar gum, ajwain (thymol), henna, sandalwood oil (restricted).
• (b) Imported into India (including adaptogens): guggul gum-resin (Commiphora wightii, partly from Pakistan/Afghanistan), liquorice root (Glycyrrhiza glabra), asafoetida (hing), saffron, clove and cinnamon/cassia, ginseng (Panax ginseng — an adaptogen), Rhodiola, Ginkgo, some essential oils and aroma chemicals. Adaptogens are herbs said to increase the body's resistance to stress (ginseng, ashwagandha, tulsi, shatavari).
• (c) Endangered medicinal plants: Saussurea costus (kuth), Nardostachys jatamansi (jatamansi), Picrorhiza kurroa (kutki), Aconitum heterophyllum (atees), Podophyllum hexandrum, Taxus wallichiana (Himalayan yew — taxol), Rauvolfia serpentina (sarpagandha), Commiphora wightii (guggul), Coptis teeta, Dioscorea deltoidea, Pterocarpus santalinus (red sanders), Gentiana kurroo, Swertia chirayita. Causes: over-collection from the wild, habitat loss, slow growth.
• (d) Prohibited from export: India's export policy (DGFT negative list) prohibits export of a notified list of wild-collected plants, their parts and derivatives (only value-added formulations or certified cultivated material may be allowed). Examples on the list include Aconitum spp., Coptis teeta, Dioscorea deltoidea, Nardostachys grandiflora, Picrorhiza kurroa, Podophyllum hexandrum, Rauvolfia serpentina, Saussurea costus, Swertia chirata, Taxus wallichiana, Pterocarpus santalinus, Panax pseudoginseng, orchids, cycads, tree ferns and Nepenthes khasiana. Check the latest DGFT list.

Quality control of herbal drugs

Quality control ensures identity, purity, safety and potency (consistent content of active/marker compounds). Parameters (as per WHO and the Ayurvedic Pharmacopoeia of India / Indian Pharmacopoeia):

1. Authentication: botanical identity — macroscopy, microscopy, DNA barcoding; voucher specimen.
2. Foreign matter (usually not more than 2%).
3. Physico-chemical: moisture (loss on drying), total ash, acid-insoluble ash, water-soluble ash, alcohol- and water-soluble extractive values, volatile oil content, swelling index, foaming index, bitterness value.
4. Phytochemical: TLC/HPTLC/HPLC fingerprint; assay of marker compounds (e.g. curcumin, sennosides).
5. Contaminants: heavy metals (lead, cadmium, arsenic, mercury), pesticide residues, microbial load and pathogens (E. coli, Salmonella), aflatoxins, residual solvents, radioactive contamination.
6. Stability and proper packaging/labelling.

Good practices: GACP (Good Agricultural and Collection Practices), GMP (Schedule T for Ayurveda, Siddha and Unani units in India), Good Laboratory Practice.

WHO guidelines for the use of herbal medicines

The World Health Organization supports the safe and effective use of traditional and herbal medicines through its Traditional Medicine Strategy (2014–2023, extended; a new strategy has been adopted — check latest) and a set of guidelines:

• Guidelines for the assessment of herbal medicines (1991) — quality, safety and efficacy assessment; long traditional use accepted as evidence for low-risk products.
• Quality control methods for herbal materials (1998, updated 2011) — the tests listed above.
• WHO guidelines on GACP for medicinal plants (2003) — cultivation, collection, harvest, primary processing, storage and documentation.
• GMP for herbal medicines and guidelines on safety monitoring (pharmacovigilance) of herbal medicines (2004) — reporting adverse reactions and herb–drug interactions.
• Guidelines for consumers on appropriate use: buy from reliable sources, follow labelled dose, inform doctors, beware of combining with modern medicines, special care in pregnancy, children and elderly; correct labelling (botanical name, part, dose, warnings, expiry).
• Regulation and registration of herbal medicines by national authorities, research and training of practitioners, protection of traditional knowledge and sustainable use of resources.

Likely exam questions

1. (Long, 8 marks) Describe the cultivation and post-harvest processing (curing) of turmeric and ginger.
2. (Long, 8 marks) Explain the quality control of herbal drugs. Add a note on WHO guidelines for herbal medicines.
3. (Short, 4 marks) How are cinnamon quills prepared?
4. (Short, 4 marks) Name five endangered medicinal plants of India.
5. (Short, 4 marks) Write a note on India's export and import of medicinal plants.

Syllabus topics (RTMNU)

• Secondary metabolites – sources, types, uses and examples of: Alkaloids, Glycosides, Tannins, Saponins, Volatile oils, Resins
• Extraction methods of crude drugs: Infusion, Decoction, Maceration, Soxhlet extraction, Distillation

Secondary metabolites

Secondary metabolites are compounds not needed for basic growth but important for defence, attraction of pollinators and adaptation; most medicinal properties of plants come from them.

(a) Alkaloids

Basic, nitrogen-containing (usually in a heterocyclic ring) compounds, mostly bitter and physiologically very active; derived from amino acids; occur as salts of organic acids. Sources/examples: morphine and codeine (Papaver somniferum — analgesic), quinine (Cinchona — antimalarial), reserpine (Rauvolfia serpentina — antihypertensive), atropine/hyoscyamine (Atropa belladonna, Datura — anticholinergic), vinblastine and vincristine (Catharanthus roseus — anticancer), caffeine (tea, coffee — stimulant), nicotine (tobacco), strychnine (Strychnos nux-vomica), colchicine (Gloriosa, Colchicum — gout), piperine (black pepper), vasicine (Adhatoda — expectorant). Types by ring: pyridine, tropane, quinoline, isoquinoline, indole, purine alkaloids. Tests: Dragendorff's (orange-red ppt), Mayer's (cream ppt), Wagner's (reddish-brown ppt), Hager's (yellow ppt).

(b) Glycosides

Compounds that on hydrolysis give a sugar (glycone) and a non-sugar part (aglycone/genin); the aglycone gives the action, the sugar affects solubility. Types and examples: cardiac glycosides — digoxin, digitoxin (Digitalis; heart failure; Keller–Killiani test), anthraquinone — sennosides (senna), aloin (aloe) — laxatives (Borntrager's test), saponin glycosides (below), cyanogenic — amygdalin (bitter almond), flavonoid — rutin, quercetin (antioxidant, capillary fragility), coumarin glycosides, isothiocyanate — sinigrin (mustard), bitter glycosides — gentiopicrin, andrographolide-type bitters.

(c) Tannins

Complex polyphenols that precipitate proteins (convert hide to leather) and give an astringent taste. Types: hydrolysable tannins (esters of gallic/ellagic acid with glucose — gallotannins; e.g. myrobalan Terminalia chebula, galls, amla) — blue-black with FeCl₃; condensed tannins (polymers of catechins; e.g. catechu/Acacia catechu, tea, cinnamon) — green-black with FeCl₃, form red phlobaphenes. Tests: gelatin test (precipitate), FeCl₃ test, Goldbeater's skin test. Uses: astringent (diarrhoea, bleeding gums, wounds), antioxidant, tanning of leather, ink, dyeing; antidote to alkaloid poisoning.

(d) Saponins

Glycosides with soap-like property — form a stable froth when shaken with water and cause haemolysis of red blood cells. Types: steroidal saponins — diosgenin from Dioscorea (raw material for steroid hormones, contraceptives), shatavarins (Asparagus racemosus), Trigonella (fenugreek); triterpenoid saponins — glycyrrhizin (liquorice, sweet), ginsenosides (ginseng), bacosides (Bacopa monnieri — memory), soapnut (Sapindus) saponins. Tests: foam test, haemolysis test. Uses: expectorants, detergents/shampoos, steroid synthesis, adjuvants, fish poisons.

(e) Volatile oils (essential oils)

Odorous, volatile oily liquids that evaporate at room temperature without leaving a stain; mainly terpenes (monoterpenes, sesquiterpenes) and phenylpropanoids; stored in oil cells, glandular hairs, ducts. Examples: clove oil (eugenol), peppermint/mint oil (menthol), lemongrass (citral), eucalyptus (1,8-cineole), sandalwood (santalols), cinnamon (cinnamaldehyde), fennel (anethole), tulsi (eugenol), rose oil. Tests: Sudan III stains red; transparent spot on filter paper disappears on evaporation. Uses: flavouring, perfumery, aromatherapy, carminatives, antiseptics, insect repellents, counter-irritants.

(f) Resins

Amorphous, brittle solids or semi-solids, insoluble in water but soluble in alcohol and organic solvents, burning with a smoky flame; formed by oxidation/polymerisation of volatile oils; produced in ducts or as exudates on injury. Types: resins (colophony/rosin from Pinus, podophyllum resin), oleo-resins (turpentine, ginger and capsicum oleoresins), gum-resins and oleo-gum-resins (guggul — Commiphora wightii, asafoetida — Ferula, myrrh), balsams (containing benzoic/cinnamic acids — benzoin, Tolu and Peru balsam). Uses: guggul for lipid lowering and arthritis, benzoin as antiseptic inhalant and in tinctures, varnishes, adhesives, incense.

Extraction methods of crude drugs

Extraction separates the active constituents from the inert plant tissue using a selective solvent (menstruum); the remaining insoluble matter is the marc.

Other methods: percolation, digestion (gentle heat maceration), supercritical fluid (CO₂) extraction, ultrasound- and microwave-assisted extraction, enfleurage for delicate flower oils.

Likely exam questions

1. (Long, 8 marks) What are alkaloids and glycosides? Give their classification, tests and medicinal uses with examples.
2. (Long, 8 marks) Describe the methods of extraction of crude drugs: infusion, decoction, maceration, Soxhlet extraction and distillation.
3. (Short, 4 marks) Write a note on tannins.
4. (Short, 4 marks) What are saponins? Give two examples.
5. (Short, 4 marks) Write a note on volatile oils.