Chemistry, tests, uses and mode of action of cardiac glycosides, steroids, alkaloids and terpenes. Pharmacognosy of Digitalis, Cinnamon, Rouwolfia, Ergot, Opium, Clove, Belladonna, Ginseng, Taxol, Artemisine and Senna.
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Pharmacognosy: Comprehensive Notes
PART A: SECONDARY METABOLITE CLASSES
1. CARDIAC GLYCOSIDES
Chemistry
Cardiac glycosides are composed of two parts:
- Aglycone (genin): A steroid nucleus (cyclopentanoperhydrophenanthrene) with a lactone ring at C-17. In cardenolides (e.g., digoxin, digitoxin) the lactone is a 5-membered butenolide ring; in bufadienolides (e.g., scillaren) it is a 6-membered alpha-pyrone.
- Glycone (sugar): 1-4 sugar units attached at C-3 of the aglycone via a glycosidic bond. Common sugars include digitoxose, cymarose, thevetose, and rhamnose. Sugars affect solubility and pharmacokinetics; the lactone ring is essential for cardiac activity.
The steroid nucleus carries hydroxyl groups at C-3 and C-14; the C-14 beta-OH is indispensable for activity.
Chemical Tests
| Test | Procedure | Result |
|---|---|---|
| Keller-Killiani test | Alcoholic extract + water + lead acetate (filter) -> CHCl3 (evaporate) -> glacial acetic acid + FeCl3 drops -> conc. H2SO4 layered below | Reddish-brown ring at junction; turns bluish-green on standing - specific for digitoxose (deoxy sugar) |
| Baljet test | Section of leaf or drug extract + sodium picrate solution | Yellow to orange colour - detects lactone ring |
| Legal test | Residue in pyridine + sodium nitroprusside + NaOH (alkaline) | Pink to red colour - detects active methylene group of lactone |
| 3,5-Dinitrobenzoic acid test | Alcoholic extract + NaOH + 2% 3,5-dinitrobenzoic acid | Pink colour - confirms cardiac glycoside |
| Kedde's test | Extract + 3,5-dinitrobenzoic acid + KOH | Purple/violet colour - confirms alpha,beta-unsaturated lactone |
| Raymond test | Extract + m-dinitrobenzene in alcohol + NaOH | Violet colour |
Mode of Action
Cardiac glycosides inhibit the Na+/K+ ATPase pump (sodium pump) on cardiac myocyte sarcolemma. This leads to:
- Intracellular Na+ accumulates.
- Na+/Ca2+ exchanger (NCX) is inhibited - less Ca2+ expelled.
- Intracellular Ca2+ rises, increasing myocardial contractility (positive inotropy).
- Vagal tone is enhanced (negative chronotropy and dromotropy), slowing heart rate and AV conduction.
Uses
- Congestive heart failure (CHF) - increases cardiac output
- Atrial fibrillation and flutter - rate control by slowing AV conduction
- Paroxysmal supraventricular tachycardia
2. STEROIDS
Chemistry
Steroids are biologically active organic compounds with the cyclopentanoperhydrophenanthrene nucleus - 17 carbon atoms arranged in four fused rings (A, B, C, D). Functional groups (methyl, hydroxyl, aldehyde, ketone) on the nucleus determine biological activity.
Classification:
- Phytosterols: Beta-sitosterol, stigmasterol (plant membranes)
- Steroidal saponins: Diosgenin (Dioscorea), glycyrrhizin (Liquorice) - triterpenoid saponins
- Steroidal alkaloids: Solanidine (Solanum)
- Cardiac aglycones: Digitogenin, gitogenin
- Steroidal hormones: Precursors synthesized from diosgenin
Chemical Tests
| Test | Procedure | Result |
|---|---|---|
| Liebermann-Burchard test | Chloroform extract + acetic anhydride + conc. H2SO4 (from side walls) | Green to blue colour - confirms sterols/triterpenes |
| Salkowski test | CHCl3 extract + conc. H2SO4 | Red or yellow ring at junction |
| Zimmermann test | m-Dinitrobenzene + alcoholic extract + alkali + heat | Violet colour - keto steroids |
| Foam test | Aqueous extract + shake vigorously | Persistent foam (1 cm) - saponins (triterpene/steroid) |
| Haemolysis test | Extract + RBC suspension | Lysis of RBCs due to saponin |
Mode of Action
- Hormonal precursors: Diosgenin from Dioscorea is used semi-synthetically to produce progesterone, cortisone, and contraceptive steroids.
- Anti-inflammatory: Steroidal saponins reduce prostaglandin synthesis.
- Adaptogenic: Some sterols modulate immune and endocrine responses.
Uses
- Source of hormonal drugs (oral contraceptives, corticosteroids, anabolic steroids)
- Hypocholesterolaemic (phytosterols compete with cholesterol absorption)
- Saponins as adjuvants in vaccines
- Digitalis steroids as cardiac drugs
3. ALKALOIDS
Chemistry
Alkaloids are nitrogen-containing basic secondary metabolites (N in heterocyclic ring), usually derived from amino acids via shikimic acid, acetate, or mevalonate pathways. They are optically active, bitter, and form salts with acids.
Classification by nitrogen heterocycle:
| Class | Ring System | Examples |
|---|---|---|
| Pyrrolidine | 5-membered N ring | Nicotine, hygrine |
| Piperidine | 6-membered N ring | Lobeline, piperine |
| Tropane | Bicyclic, N-methyl | Atropine, cocaine, scopolamine |
| Isoquinoline | Benzene + pyridine | Morphine, codeine, papaverine, emetine |
| Indole | Benzene + pyrrole | Reserpine, ergometrine, vincristine, strychnine |
| Quinoline | Benzene + pyridine | Quinine, camptothecin |
| Xanthine (Purine) | Bicyclic N | Caffeine, theophylline |
| Imidazole | 5-membered 2N | Pilocarpine |
| Steroidal | Steroid backbone | Solanine, veratrum alkaloids |
Chemical Tests (General)
| Test | Reagent | Result |
|---|---|---|
| Dragendorff's test | Potassium bismuth iodide | Orange-red precipitate |
| Mayer's test | Potassium mercuric iodide | Cream/white precipitate |
| Wagner's test | Iodine-potassium iodide | Reddish-brown precipitate |
| Hager's test | Saturated picric acid | Yellow precipitate |
Specific Alkaloid Tests
| Test | Target | Result |
|---|---|---|
| Vitali-Morin test | Tropane alkaloids (atropine) | Fuming HNO3 + alcoholic KOH -> violet |
| Van Urk's test | Ergot alkaloids (indole) | p-DMAB in dil. H2SO4 + FeCl3 -> blue |
| Thalloquin test | Quinine (quinoline) | Br2 water + dil. NH3 -> emerald green |
| Murexide test | Caffeine (purine) | KClO3 + HCl -> evaporate -> NH3 vapours -> purple |
| Marquis test | Morphine/opioids | H2SO4 + formaldehyde -> purple to violet |
Mode of Action
- Receptor agonists/antagonists: Atropine (muscarinic), morphine (opioid), nicotine (nicotinic)
- Enzyme inhibitors: Physostigmine (acetylcholinesterase), vincristine (tubulin polymerization)
- CNS depressants/stimulants: Caffeine (phosphodiesterase inhibition), cocaine (dopamine reuptake)
- Antimitotic: Vincristine/vinblastine, colchicine (tubulin binding)
Uses
- CNS drugs, analgesics, antihypertensives, antimalarials, antineoplastics, muscle relaxants
4. TERPENES
Chemistry
Terpenes follow the isoprene rule - built from C5 isoprene (2-methyl-1,3-butadiene) units. Synthesized via the mevalonate pathway (cytoplasm - sesqui and triterpenes) and MEP/DXP pathway (plastid - mono and diterpenes).
Classification:
| Class | Carbon | Examples |
|---|---|---|
| Monoterpenes | C10 (2 isoprene) | Menthol, camphor, geraniol, thymol |
| Sesquiterpenes | C15 (3 isoprene) | Artabsin, parthenolide, farnesol |
| Diterpenes | C20 (4 isoprene) | Taxol (paclitaxel), retinol (Vit A), gibberellin |
| Sesterterpenes | C25 | Marine terpenes |
| Triterpenes | C30 (6 isoprene) | Oleanolic acid, glycyrrhizin, squalene, sterols |
| Tetraterpenes | C40 (8 isoprene) | Carotenoids (beta-carotene), lycopene |
| Polyterpenes | >C40 | Rubber, gutta-percha |
Chemical Tests
| Test | Target | Result |
|---|---|---|
| Liebermann-Burchard | Triterpenes/steroids | Green-blue with acetic anhydride + H2SO4 |
| Salkowski test | Triterpenes | Red/yellow at CHCl3-H2SO4 junction |
| Carr-Price test | Tetraterpenes (carotenoids) | Blue colour with SbCl3 in CHCl3 |
| Foam test | Triterpenoid saponins | Persistent foam in aqueous extract |
| Conc. H2SO4 test | Monoterpenes/essential oils | Yellow/brown colour, characteristic smell |
Mode of Action
- Monoterpenes (volatile oils): Antimicrobial (disrupting cell membranes), carminative, antispasmodic
- Sesquiterpene lactones: Anti-inflammatory (alkylating NF-kB), antimalarial (artemisinin - endoperoxide bridge forms radicals in Plasmodium)
- Diterpenes (Taxol): Stabilizes microtubules, prevents depolymerization -> mitotic arrest
- Triterpenes: Adaptogenic, immunomodulatory, anti-inflammatory (ginsenosides, glycyrrhizin)
- Tetraterpenes: Antioxidant (carotenoids quench singlet oxygen)
PART B: PHARMACOGNOSY OF INDIVIDUAL DRUGS
1. DIGITALIS (Foxglove)
| Feature | Details |
|---|---|
| Synonyms | Foxglove, Purple foxglove, Fairy fingers |
| Biological source | Dried leaves of Digitalis purpurea (Linn.) or Digitalis lanata (Ehrhart), Family: Scrophulariaceae |
| Parts used | Leaves (first-year rosette leaves, harvested before flowering) |
| Habitat | Hilly areas of Europe, UK, USA, India (Himalayas) |
Chemical Constituents:
- Primary glycosides: Purpurea glycoside A (-> digitoxin), Purpurea glycoside B (-> gitoxin) in D. purpurea; Lanatoside A, B, C (-> digoxin from lanatoside C) in D. lanata
- Secondary glycosides (more stable, therapeutically significant): Digitoxin, Gitoxin, Gitaloxin
- Aglycones: Digitoxigenin, gitoxigenin
- Also contains digitonin (saponin), digitoflavone
Chemical Tests:
- Baljet test: Yellow-orange with sodium picrate
- Keller-Killiani test: Reddish-brown ring (turns bluish-green) - detects digitoxose
- Legal test: Pink/red in pyridine-sodium nitroprusside-NaOH system
Mode of Action:
- Inhibits sarcolemmal Na+/K+ ATPase -> increases intracellular Ca2+ -> positive inotropy
- Increases vagal tone -> slows SA node and AV conduction (negative chronotropy, negative dromotropy)
- At high doses: arrhythmogenic (increased automaticity of Purkinje fibers)
Uses:
- Congestive heart failure (CHF)
- Atrial fibrillation and flutter (rate control)
- Paroxysmal atrial tachycardia
- Diuretic effect (secondary to improved cardiac output)
Storage: In moisture-proof, well-closed containers; moisture destroys glycosides.
2. CINNAMON
| Feature | Details |
|---|---|
| Synonyms | Ceylon cinnamon, True cinnamon |
| Biological source | Dried inner bark of Cinnamomum zeylanicum (Breyne) / Cinnamomum verum, Family: Lauraceae |
| Parts used | Bark (inner, dried in quill form), bark oil, leaf oil |
| Habitat | Sri Lanka (Ceylon), India (Kerala, Malabar coast), South-East Asia |
Chemical Constituents:
- Bark oil (60-75%): trans-Cinnamaldehyde (major, 60-90%), eugenol (<10%), linalool, beta-caryophyllene
- Leaf oil: Eugenol (70-95%), cinnamaldehyde (small amounts)
- Tannins: Condensed tannins (procyanidins)
- Diterpenes: Cinzeylanol, cinzeylanone
- Polyphenols: Catechins, epicatechins
- Mucilage, starch, calcium oxalate
Chemical Tests:
- Alcoholic extract + FeCl3 -> dark green/blue-green (tannins)
- Volatile oil + bromine water -> decolourization (unsaturation)
- Cinnamaldehyde gives positive Schiff's test for aldehydes
- Microscopically: calcium oxalate crystals (acicular/prismatic), starch grains, oil cells
Mode of Action:
- Cinnamaldehyde: antimicrobial (disrupts bacterial cell membrane), antifungal
- Stimulates peripheral circulation (rubefacient)
- Polyphenols and type-A procyanidins: insulin-sensitizing effect (enhance insulin receptor signalling, inhibit phosphotyrosine phosphatase)
- Anti-inflammatory: inhibits arachidonic acid metabolism
- Carminative: relaxes smooth muscle of GIT, reduces flatulence
Uses:
- Carminative and stomachic (flavouring agent in antacids, GIT preparations)
- Antispasmodic
- Antiseptic (in oral hygiene products)
- Anti-diabetic (polyphenol extract - improves glycaemic control)
- Antidiarrheal
- Flavouring agent in food and pharmaceuticals
3. RAUWOLFIA (Sarpagandha)
| Feature | Details |
|---|---|
| Synonyms | Sarpagandha, Snakeroot, Serpentwood |
| Biological source | Dried roots of Rauwolfia serpentina (Benth.), Family: Apocynaceae |
| Parts used | Roots (dried) |
| Habitat | India (foothills of Himalayas, Bengal, Bihar, Assam), Myanmar, Java |
Chemical Constituents (~50 alkaloids):
| Group | Alkaloids |
|---|---|
| Indole alkaloids (major) | Reserpine (0.1-1%), ajmaline, ajmalicine, serpentine |
| Yohimbane type | Rauwolscine, yohimbine |
| Heteroyohimbane | Ajmalicine, tetrahydroalstonine |
- Reserpine is the principal alkaloid (~0.15-0.2%)
- Also contains steroidal alkaloids and saponins
Chemical Tests:
- General alkaloid tests: Dragendorff's (orange), Mayer's (cream), Wagner's (brown)
- Van Urk's test: Specific for indole alkaloids - p-DMAB in H2SO4 + FeCl3 -> blue colour
- Reserpine fluoresces under UV (yellow-green)
- FeCl3 test on methanolic extract - coloured complex
Mode of Action:
- Reserpine: Irreversibly inhibits vesicular monoamine transporter (VMAT) -> depletes catecholamines (norepinephrine, dopamine) and serotonin from presynaptic vesicles in CNS and peripheral adrenergic neurons -> reduced sympathetic tone -> antihypertensive and antipsychotic effect
- Ajmaline: Sodium channel blocker (Class IA antiarrhythmic)
- Yohimbine: Alpha-2 adrenergic antagonist
Uses:
- Reserpine: antihypertensive, antipsychotic (now largely replaced by modern drugs)
- Ajmaline: antiarrhythmic (Wolff-Parkinson-White syndrome)
- Ajmalicine: cerebral vasodilator
- Reserpine historically used in psychiatry (first antipsychotic drug - discovered 1952)
4. ERGOT
| Feature | Details |
|---|---|
| Synonyms | Secale cornutum, Ergot of rye, Spurred rye |
| Biological source | Dried sclerotium (compact mycelial mass) of fungus Claviceps purpurea (Tulasne), growing on rye Secale cereale and other grasses. Family: Clavicipitaceae (Hypocreaceae) |
| Parts used | Sclerotium (ergot body - the purple-black horn) |
| Habitat | Northern Europe (Germany, Russia, Spain), USA, cultivated on rye |
Chemical Constituents (Ergot alkaloids - all contain the tetracyclic ergoline nucleus):
| Group | Examples |
|---|---|
| Lysergic acid group | Ergotamine, ergocristine, ergocornine, ergocryptine (ergotoxine group), ergosine |
| Dihydrogenated (semisynthetic) | Dihydroergotamine (DHE), dihydroergotoxine |
| Clavine alkaloids | Agroclavine, elymoclavine |
| Lysergic acid amide derivatives | Ergonovine (ergometrine), methylergonovine |
| Also: | Histamine, tyramine, acetylcholine, fatty acids |
Chemical Tests:
- Van Urk's test: p-Dimethylaminobenzaldehyde (p-DMAB) + dil. H2SO4 + trace FeCl3 -> blue colour (specific for indole alkaloids)
- Keller's test: Blue coloration with H2SO4
- Ergotamine exhibits fluorescence (blue-green under UV)
- Sabouraud test: Used for identification on culture
Mode of Action:
- Ergometrine (ergonovine): Strong, prolonged uterine contraction (agonist at 5-HT2 and alpha-adrenergic receptors on uterine muscle)
- Ergotamine: Partial agonist/antagonist at 5-HT1B/1D receptors (vasoconstriction) and alpha-adrenergic receptors; used in migraine
- Dihydroergotoxine: Alpha-blocker, peripheral vasodilator
- Bromocriptine (semisynthetic): Dopamine D2 agonist - used in Parkinson's disease and hyperprolactinaemia
Uses:
- Obstetrics: Ergometrine/methylergometrine - control of postpartum haemorrhage and uterine atony
- Migraine: Ergotamine (with caffeine - Cafergot)
- Peripheral vascular disorders: Dihydroergotamine
- Parkinson's disease/hyperprolactinaemia: Bromocriptine
- Historical/toxic: Ergotism ("St. Anthony's Fire") - gangrenous or convulsive form from contaminated rye
5. OPIUM
| Feature | Details |
|---|---|
| Synonyms | Crude opium, Raw opium, Papaver latex |
| Biological source | Air-dried milky latex obtained by incising the unripe capsules of Papaver somniferum (Linn.), Family: Papaveraceae |
| Parts used | Latex (from unripe seed capsule) |
| Habitat | Turkey, India (Madhya Pradesh, Rajasthan, UP), China, Afghanistan |
Chemical Constituents (>25 alkaloids, 10-30% total):
| Group | Alkaloids | Pharmacological Action |
|---|---|---|
| Phenanthrene group | Morphine (4-21%), Codeine (0.8-2.5%), Thebaine (0.5-2%) | Narcotic analgesics |
| Benzylisoquinoline group | Papaverine (0.5-1%), Noscapine/Narcotine (2-9%), Narceine | Antispasmodic, antitussive |
- Also: Meconic acid (distinctive marker for opium identification), meconine, albumin, gums, resins, wax
Chemical Tests:
- Marquis test: H2SO4 + formaldehyde -> purple/violet (morphine)
- Mecke's test: Selenious acid in H2SO4 -> blue-green (morphine)
- Froehde's test: Molybdic acid in H2SO4 -> purple (morphine), yellow (codeine)
- Meconate test: Opium + FeCl3 -> blood-red colour (meconic acid - characteristic of opium)
- Papaverine: orange-red with conc. H2SO4
Mode of Action:
- Morphine: Agonist at mu (mu), kappa, and delta opioid receptors (GPCRs); inhibits adenylyl cyclase, increases K+ conductance (hyperpolarization), decreases Ca2+ entry -> reduces pain transmission, causes euphoria, respiratory depression, constipation, antitussive
- Codeine: Prodrug - demethylated to morphine by CYP2D6; also has direct opioid activity
- Papaverine: Inhibits phosphodiesterase -> increases cAMP -> smooth muscle relaxation (antispasmodic)
- Thebaine: Used as semisynthetic precursor (oxycodone, naloxone, buprenorphine)
Uses:
- Morphine: Severe pain relief (cancer pain, post-operative), pulmonary oedema (reduces preload), antidiarrheal
- Codeine: Antitussive (cough suppressant), mild analgesic
- Papaverine: Antispasmodic, erectile dysfunction (intracavernosal injection)
- Noscapine: Antitussive (non-narcotic)
- Thebaine: Precursor for semisynthetic opioids
6. CLOVE
| Feature | Details |
|---|---|
| Synonyms | Lavang, Caryophyllus |
| Biological source | Dried flower buds of Syzygium aromaticum (Linn.) Merr. & Perry (syn. Eugenia caryophyllus), Family: Myrtaceae |
| Parts used | Dried flower buds, clove oil |
| Habitat | Moluccas (Maluku Islands, Indonesia), Zanzibar, Madagascar, Sri Lanka, India (Kerala) |
Chemical Constituents:
- Volatile oil (15-21%): Eugenol (72-90%), eugenyl acetate (5-15%), beta-caryophyllene (5-12%), methyl eugenol, chavicol
- Fixed oil: Oleanolic acid
- Tannins: Gallotannins, ellagitannins
- Flavonoids: Quercetin, kaempferol
- Triterpenoids: Oleanolic acid, crategolic acid
Chemical Tests:
- Eugenol gives positive FeCl3 test (deep green - phenolic OH)
- Volatile oil + KMnO4 decolorizes (unsaturation)
- Clove oil + concentrated H2SO4 -> brown resinous mass
- Microscopically: Oil cells, stone cells, vascular bundles with sclerenchyma
Mode of Action:
- Eugenol: Inhibits cyclooxygenase (COX) -> anti-inflammatory, analgesic; blocks voltage-gated Na+ channels -> local anaesthetic; antimicrobial (disrupts bacterial cell membrane integrity)
- Beta-caryophyllene: Agonist at CB2 (cannabinoid) receptors -> anti-inflammatory
- Eugenol also chelates Ca2+ -> antispasmodic effect on smooth muscle
Uses:
- Dental: Oil of cloves (eugenol) as dental analgesic (toothache drops), obtundant in dentistry, cavity liner (ZOE - zinc oxide eugenol cement)
- Antiseptic: In mouthwashes, toothpastes
- Carminative: Reduces flatulence
- Preservative: In food and pharmaceuticals
- Flavouring: In confectionery, beverages, perfumery
- Anti-nausea (morning sickness)
7. BELLADONNA (Deadly Nightshade)
| Feature | Details |
|---|---|
| Synonyms | Deadly nightshade, Atropa, Belladonna herb |
| Biological source | Dried leaves and flowering tops of Atropa belladonna (Linn.), Family: Solanaceae |
| Parts used | Leaves, root (Belladonna root) |
| Habitat | Central and Southern Europe, Iran, North Africa, cultivated in India (Himachal Pradesh, J&K) |
Chemical Constituents:
- Tropane alkaloids (0.35%):
- l-Hyoscyamine (major, racemizes to dl-atropine on extraction)
- Atropine (dl-hyoscyamine)
- Scopolamine (hyoscine) - in smaller amounts
- Belladonnine, apoatropine, cuscohygrine
- Also: tannins, flavonoids, steroidal alkaloids (solanine)
Chemical Tests:
- Vitali-Morin test: Fuming HNO3 -> evaporate -> alcoholic KOH solution -> violet colour (specific for tropane alkaloids - due to formation of dinitrophenyl derivative)
- Dragendorff's: Orange precipitate (general alkaloid)
- Atropine gives positive Mayer's and Wagner's tests
- Microscopically: Anomocytic stomata, calcium oxalate crystals (microsphenoidal), glandular trichomes (multicellular head)
Mode of Action:
- Atropine/Hyoscyamine: Competitive antagonist at muscarinic acetylcholine receptors (M1, M2, M3) -> blocks parasympathetic effects:
- Heart: increased rate (tachycardia), increased AV conduction
- Smooth muscle: reduced GIT motility, bronchodilation, reduced secretions (salivary, gastric, bronchial, sweat)
- Eye: mydriasis (dilated pupils), cycloplegia (paralysis of accommodation)
- CNS (at high doses): restlessness, delirium
- Scopolamine: More lipophilic, penetrates CNS -> antiemetic, sedative, amnesia; used in motion sickness
Uses:
- Atropine: Antidote for organophosphate poisoning and nerve agent exposure; preanaesthetic medication (reduces secretions); bradycardia; antispasmodic; ophthalmology (mydriasis)
- Scopolamine: Motion sickness (transdermal patch), preanaesthetic, antiemetic
- Belladonna extract: Antispasmodic preparations, cough linctus, haemorrhoid suppositories
8. GINSENG
| Feature | Details |
|---|---|
| Synonyms | Korean ginseng, Asian ginseng, Man-root, Panax |
| Biological source | Dried roots of Panax ginseng C.A. Meyer (Asian) or Panax quinquefolius (American ginseng), Family: Araliaceae |
| Parts used | Roots (main and lateral; white or red ginseng based on processing) |
| Habitat | Korea, China, Manchuria, Japan, Eastern Siberia, cultivated widely |
Chemical Constituents:
- Triterpenoid saponins (ginsenosides/panaxosides): Over 40 types; classified as Rb1, Rb2, Rc, Rd (protopanaxadiol group) and Rg1, Re, Rf, Rg2 (protopanaxatriol group) - these are dammarane-type triterpene saponins
- Polyacetylenes: Panaxynol, panaxydol (antifungal, antitumour)
- Polysaccharides: Panaxans (hypoglycaemic)
- Peptidoglycans: Panaxans A-E
- Volatile oil: Panacene, beta-elemene
- Vitamins, minerals, phytosterols: Beta-sitosterol, stigmasterol
Chemical Tests:
- Liebermann-Burchard test: Green-blue colour (triterpenoid saponins/sterols)
- Foam test: Persistent froth in aqueous extract (saponins)
- Haemolysis test: Lysis of RBCs (saponin action)
- TLC with anisaldehyde-H2SO4 spray -> characteristic spots (Rg1 and Rb1 reference standards)
Mode of Action:
- Ginsenosides: Modulate multiple receptor systems - Rb1 inhibits CNS, Rg1 stimulates CNS; act on NMDA, nicotinic receptors; modulate nitric oxide synthesis
- Adaptogenic effect: Normalize HPA (hypothalamic-pituitary-adrenal) axis; enhance cortisol and ACTH response under stress; improve mitochondrial function
- Immunomodulation: Activate NK cells, T-lymphocytes, macrophages; enhance interferon production
- Antioxidant: Ginsenosides and polyacetylenes scavenge free radicals
- Hypoglycaemic: Panaxans stimulate insulin release and increase peripheral glucose uptake
Uses:
- Adaptogen - physical and mental stress, fatigue
- Immune enhancement
- Adjunct in diabetes (hypoglycaemic)
- Erectile dysfunction (ginsenoside Rg1 - NO-mediated)
- Cognitive enhancement (memory, dementia)
- Antitumour (adjunct in cancer care)
9. TAXOL (Paclitaxel)
| Feature | Details |
|---|---|
| Synonyms | Paclitaxel, Taxol (brand name) |
| Biological source | Bark and needles of Taxus brevifolia Nutt. (Pacific Yew), also T. baccata, T. wallichiana (Himalayan Yew), Family: Taxaceae |
| Parts used | Bark (original source - now mostly from needles + semisynthesis) |
| Habitat | Pacific coast of North America (Oregon, Washington), Himalayas, Europe |
Chemical Constituents:
- Taxol (paclitaxel): A diterpenoid taxane - complex diterpene with a taxane ring (6-8-6 tricyclic ring system) and a phenylisoserine ester side chain at C-13 (essential for activity)
- Baccatin III: Taxane precursor used for semisynthesis
- 10-Deacetylbaccatin III (10-DAB): Found in needles/leaves; semisynthetic precursor of docetaxel and paclitaxel
- Other taxanes: cephalomannine, taxol B
Chemical Tests:
- TLC on silica gel with UV detection
- HPLC fingerprinting (standard method)
- UV spectroscopy (characteristic absorption at 228 nm)
- Mass spectrometry for molecular weight confirmation (MW = 853.9)
Mode of Action:
- Unique mechanism: Paclitaxel stabilizes microtubules by binding to the beta-tubulin subunit (binds to the inner surface of the microtubule lumen at a site distinct from colchicine and vinca alkaloids)
- Prevents microtubule depolymerization during mitosis -> cells arrested in G2/M phase -> apoptosis
- Also promotes abnormal microtubule bundles, disrupting cell division
Uses:
- Ovarian cancer (first-line)
- Breast cancer (adjuvant and metastatic)
- Non-small cell lung cancer (NSCLC)
- Kaposi's sarcoma
- Gastric, cervical, pancreatic cancers (second line)
- Nab-paclitaxel (albumin-bound) improves solubility and delivery
- Docetaxel (semisynthetic analog) has similar indications
10. ARTEMISININ (Artemisin)
| Feature | Details |
|---|---|
| Synonyms | Qinghaosu, Artemisinine |
| Biological source | Leaves and flowering tops of Artemisia annua L. (Sweet Annie / Sweet wormwood), Family: Asteraceae (Compositae) |
| Parts used | Aerial parts (leaves; harvested at early flowering) |
| Habitat | China, Vietnam, India, East Africa; cultivated globally |
Chemical Constituents:
- Artemisinin: A sesquiterpene lactone with an unusual endoperoxide bridge (-O-O-) in a 1,2,4-trioxane ring system; C15H22O5; soluble in non-polar solvents, poorly soluble in water
- Artemisitene: Closely related compound
- Volatile oils: camphor, beta-caryophyllene, artemisia ketone, borneol
- Flavonoids: artemetin, casticin
Chemical Tests:
- Endoperoxide detection: Reaction with KI -> liberated iodine (bleaches starch solution)
- Extract + NaOH -> yellow colour (alkaline hydrolysis of lactone)
- TLC with vanillin-H2SO4 spray -> purple spot
- HPLC with derivatization (post-column) or LC-MS
Mode of Action:
- Artemisinin's endoperoxide bridge is activated by heme iron (Fe2+) present inside Plasmodium-infected RBCs (from haemoglobin digestion)
- Fe2+ cleaves the O-O bond via Fenton-like reaction -> generates highly reactive free radicals (carbon-centred and oxygen radicals)
- These radicals alkylate and damage parasite proteins (PfATP6 - sarcoplasmic/ER Ca2+ ATPase of Plasmodium), disrupt mitochondrial function and haem detoxification, causing parasite death
- Also inhibits proteasome and activates unfolded protein response in Plasmodium
Uses:
- Falciparum malaria (including multidrug-resistant strains) - WHO first-line treatment
- Artemisinin-based Combination Therapies (ACTs): Artemether+lumefantrine, artesunate+amodiaquine, dihydroartemisinin+piperaquine
- Severe malaria (parenteral artesunate)
- Research: anticancer activity (promotes ROS-mediated cancer cell apoptosis)
- Nobel Prize 2015: Tu Youyou awarded for discovery of artemisinin
11. SENNA
| Feature | Details |
|---|---|
| Synonyms | Cassia senna, Alexandrian senna, Tinnevelly senna |
| Biological source | Dried leaflets of Cassia acutifolia Delile (Alexandrian senna) or Cassia angustifolia Vahl (Tinnevelly senna / Indian senna), Family: Leguminosae (Caesalpiniaceae) |
| Parts used | Leaflets and pods (Senna pods = Cassia pods) |
| Habitat | C. acutifolia: Sudan, Egypt; C. angustifolia: India (Tinnevelly district, Tamil Nadu), Pakistan |
Chemical Constituents:
- Anthraquinone glycosides (sennosides): Sennoside A and Sennoside B (primary active constituents, 2.5-3% minimum by IP/BP); also sennoside C and D
- Free anthraquinones: Rhein, aloe-emodin, chrysophanol, emodin (formed after hydrolysis)
- Naphthalene glycosides: Tinnevellin glycoside (in Tinnevelly senna)
- Mucilage, flavonoids (kaempferol, isorhamnetin), calcium oxalate
Chemical Tests:
- Borntrager's test: 1 g drug + 5-10 mL dil. HCl -> boil 10 min -> filter -> extract with CCl4/benzene -> add equal volume of NH3 -> pink/red colour in ammoniacal layer (anthraquinone glycosides)
- Modified Borntrager's test: Same but using oxidizing conditions for anthraquinone precursors (e.g., K2Cr2O7 or FeCl3 before extraction)
- FeCl3 test -> brown/black (phenolic compounds)
- Microscopically: paracytic stomata, unicellular curved trichomes, rosette calcium oxalate crystals, palisade cells
Mode of Action:
- Sennosides are prodrugs - hydrolysed by colonic bacteria (beta-glucosidases) to rheinanthrone (active metabolite)
- Rheinanthrone acts on large intestinal mucosa:
- Irritant/stimulant laxative: Increases smooth muscle peristalsis and tone in colon (stimulant cathartic)
- Anti-absorptive: Inhibits Na+/K+ ATPase in colonic epithelium -> reduces water and electrolyte absorption
- Secretory: Increases water and electrolyte secretion into colon
- Onset of action: 6-12 hours (time for bacterial hydrolysis in colon)
Uses:
- Constipation (short-term treatment)
- Bowel preparation before colonoscopy/radiography
- Post-operative bowel regulation
- Hepatic encephalopathy (combined with lactulose)
- Compound senna preparations (e.g., compound senna granules)
- Caution: Long-term use causes hypokalaemia, melanosis coli, tolerance
QUICK REFERENCE: CHEMICAL TESTS SUMMARY TABLE
| Test | Detects | Result |
|---|---|---|
| Keller-Killiani | Cardiac glycosides (deoxy sugars) | Reddish-brown -> bluish-green |
| Baljet | Cardiac glycosides (lactone) | Yellow-orange with sodium picrate |
| Legal | Cardiac glycosides (lactone) | Pink-red |
| Kedde's | Alpha,beta-unsaturated lactone | Violet |
| Borntrager's | Anthraquinone glycosides | Pink/red in alkaline layer |
| Liebermann-Burchard | Steroids/triterpenes | Green to blue |
| Salkowski | Steroids | Red/yellow at junction |
| Zimmermann | Keto-steroids | Violet |
| Foam test | Saponins | Persistent foam |
| Dragendorff's | Alkaloids | Orange precipitate |
| Mayer's | Alkaloids | Cream precipitate |
| Wagner's | Alkaloids | Brown-red precipitate |
| Hager's | Alkaloids | Yellow precipitate |
| Vitali-Morin | Tropane alkaloids | Violet |
| Van Urk's | Ergot/indole alkaloids | Blue |
| Marquis | Morphine | Purple/violet |
| Thalloquin | Quinine | Emerald green |
| Murexide | Caffeine (purines) | Purple |
| Carr-Price | Carotenoids | Blue with SbCl3 |
BIOSYNTHETIC PATHWAYS (Summary)
| Secondary Metabolite | Biosynthetic Pathway | Key Intermediates |
|---|---|---|
| Alkaloids | Shikimic acid / Amino acid (tyrosine, tryptophan, ornithine) | Strictosidine, dopamine, ornithine |
| Terpenes (mono, di) | MEP (Methylerythritol phosphate) pathway in plastids | IPP, DMAPP, GPP, GGPP |
| Terpenes (sesqui, tri) | Mevalonate (MVA) pathway in cytoplasm | Mevalonate, FPP, squalene |
| Cardiac glycosides | Mevalonate -> cholesterol -> steroidal nucleus + sugar addition | Cholesterol, pregnane |
| Anthraquinones (senna) | Polyketide (Acetate-malonate) or Shikimic acid pathway | Emodin anthrone, rhein |
| Eugenol (clove) | Shikimic acid / Phenylpropanoid pathway | Phenylalanine, cinnamic acid |
Sources: Braunwald's Heart Disease; Pharmacognosy-I Unit IV (Dr. Nisha Sharma, CSJMU); D.Pharm Pharmacognosy Notes (AIPER Odisha); Wikipedia - Cardiac Glycosides; IntechOpen - Cardiac Glycosides in Medicinal Plants; Annamalai University Pharmacognosy & Phytochemistry; Textbook of Pharmacognosy and Phytochemistry (Biren Shah & Avinash Seth)
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