PHARMACOGNOSY OF ALKALOIDS
Alkaloids are basic nitrogen containing compounds obtained from plants, animals & microorganisms having a marked physiological action
?They answer the following chemical tests:
? Mayer’s reagent- (potassium mercuric iodide)——cream coloured precipitate
?Wagner’s reagent- (iodine in potassium iodide)——-reddish brown precipitate
?Hager’s reagent- (salt solution of picric acid)———–yellow precipitate
?Dragendorf’s reagent- (potassium bismuth iodide)———reddish brown precipitate
?Caffeine is a pseudo alkaloid drug which does not answer this test.
TYPES OF ALKALOIDS
?TRUE ALKALOIDS
? PROTO ALKALOIDS
eg- ephedrine
? PSEUDO ALKALOIDS
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INDOLE ALKALOIDS
?ERGOT / ARGOT / ST. ANTHONY’S FIRE
?BIOLOGICAL SOURCE: schlerotium of fungus claviceps purpurea, at the ovary of rye plant secale cereale
Family: graminae (fungus belongs to family clavicipitaceae)
?Chemistry: Derivatives of lysergic acid. Water soluble ones are ergometrine & ergometrinine
Water insoluble ones are ergotamine & ergotoxine. Only the levo isomer is active
?Uses: Ergometrine is an oxytocic drug but its methyl derivative is preferred as it causes less hypertension. Ergotamine is analgesic in migraine
?Chemical Test:
1⃣ Gives a blue colour with Van Curk’s reagent (para dimethyl amino benzaldehyde)
2⃣ Gives blue fluorescence in water
?VINCA / PERIWINKLE
?BIOLOGICAL SOURCE: aerial parts of catharanthus roseus
Family: apocynaceae
?Chemistry: Indole alkaloids such as vinblastine, vincristine, ajamlicine & serpentine
?Use: Potent anti cancer agent, hypotensive & anti diabetic
?NUXVOMICA
?BIOLOGICAL SOURCE: dried seeds of strychnos nuxvomica
?Family: loganiaceae
?Chemistry: Contains two main indole alkaloids strychnine & brucine
?Use: Rarely used as a nerve tonic as it is poisonous in large doses
?Chemical Test:
1⃣. Section when treated with concentrated HNO3 shows a yellow colour with brucine
2⃣ Section when treated with ammonium vanadate & H2SO4 shows a purple colour with strychnine
3⃣ Strychnine when treated with H2SO4 & K2Cr2O7 develops a violet to yellow colour
?RAUWOLFIA / SARPAGANDHA
?BIOLOGICAL SOURCE: dried roots of rauwolfia serpentina
?Family: apocynaceae
?Chemistry: Reserpine, ajamlicine, serpentine
?Use: Antihypertensive by preventing uptake of adrenaline
?Chemical Test:
1⃣Freshly fractured surface of the root when treated with concentrated HNO3 shows red coloured medullary rays
2⃣Reserpine gives a violet colour with vanillin in acetic acid
?TROPANE ALKALOIDS
?BELLADONA
?BIOLOGICAL SOURCE: dried leaves of atropa belladonna
?Family: solanaceae
?Chemistry: Atropine, hyoscyanine, belladonine
?Use: Atropine is a parasympatholytic, thus decreases secretion & spasms
?Chemical Test:
1⃣Vitali morin test – to the drug fuming nitric acid is added & it is evaporated to dryness.
2⃣Methanolic KOH is added to the acetone solution of the nitrated residue. It develops a violet colour
?STRAMONIUM
?BIOLOGICAL SOURCE: dried leaves & flowering tops of datura stramonium
Family: solanaceae
?Microscopic Characters:
Dorsiventral leaf Collenchyma above & below the mid rib
Unicellular covering & glandular trichomes Xylem surrounded by phloem Anisocytic stomata
?Chemistry: Hyoscine, atropine, belladonine
?Use: Hyoscine is an anti emetic
?Chemical Test: Vitali morin test
?COCA LEAVES
?BIOLOGICAL SOURCE: dried leaves of erythroxylon coca (bolivian variety) Erythroxylon truxillense (Peruvian variety)
Family: erythroxylaceae
?Microscopic Characters:
Dorsiventral leaf. Collenchyma above & below mid rib. Xylem surrounded by phloem & pericyclic fibres. Paracytic stomata
?Chemistry: Cocaine, cinnamoyl cocaine, tropocaine, benzoylecgonine
?Use: Local anaesthetic
?Chemical Test: Drug powder when heated with concentrated H2SO4 gives a typical odour of methyl benzoate
?QUINAZOLINE ALKALOIDS
?VASAKA LEAF / ADULSA
?BIOLOGICAL SOURCE: dried & fresh leaves of adhatoda vasica
Family: acanthaceae
?Chemistry: Vasicine, vasicinone & adhatodic acid
?Uses: Vasicine is an expectorant. It gets oxidized to vasicinone which in an abortifacient in large doses, otherwise a bronchodilator
?PYRIDINE ALKALOIDS
?LOBELIA HERB / INDIAN TOBACCO / ASTHMA WEED
?BIOLOGICAL SOURCE: dried aerial parts of lobelia nicotianefolia
Family: Campanulaceae
?Chemistry: Lobeline, lobelidine & isolobanine
?Use: Respiratory stimulant
?Chemical Test:
1⃣ lobeline solution if heated gives typical odour of acetophenone
2⃣ lobeline in H2SO4 when treated with formaldehyde develops red colour
?IMIDAZOLE ALKALOIDS
?PILOCARPUS
?BIOLOGICAL SOURCE: dried leaves of pilocarpus jaborandi Pilocarpus microphyllus
Family: rutaceae
?Chemistry: Contains pilocarpine, pseudopilocarpine, pilosine & limonene
?Uses: Antagonist to atropine, causes miosis, increases salivation & sweating
?INDOLE ALKALOIDS
?CALABAR BEANS
?BIOLOGICAL SOURCE: dried type seeds of physostigma venenosum
Family: leguminosae
GEOGRAPHICAL SOURCE: Africa
?Chemistry: Contains physostigmine, starch & proteins
?Use: Helps in contraction of pupil, retards respiration & causes bradycardia
?OPIUM / POPPY PLANT
?BIOLOGICAL SOURCE: dried latex obtained from capsules of papaver somniferum
Family: papaveraceae
?Chemistry: Contains phenanthrene type of alkaloids such as morphine & codeine & benzyl isoquinoline type of alkaloids such as papaverine & noscapine. These occur as salts of meconic acid
?Use: Morphine is a narcotic analgesic & stimulant. Codeine is an anti tussive. Papverine is a smooth muscle relaxant
?CINCHONA BARK / JESUIT’S BARK / PERUVIAN BARK
?BIOLOGICAL SOURCE: dried bark of cultivated trees of cinchona calisaya ,Cinchona officinalis, Cinchona ledgeriana, Cinchona succirubra
Family: rubiaceae
?Microscopic Characters: Cork cells are thin walled. Cortex has phloem fibres. Medullary rays with radially arranged cells. Idioblast of calcium oxalate is a specific characteristic. Starch grains in parenchymatous tissues
Stone cells rarely present
?Chemistry: Contains quinine, quinidine, cinchonine & cinchonidine. Also contains quinic acid & cinchotannic acid
?Chemical Test:
1⃣n heating the drug in a dry test tube with glacial acetic acid, purple vapours are produced
2⃣ Thalleoquin test: drug + bromine water + dilute ammonia gives an emerald green colour
3⃣Drug when treated with quinidine solution gives a white precipitate with silver nitrate which is soluble in nitric acid
?Uses: Anti malarial, anti pyretic, quinine is used in arrythmias against atrial fibrillation
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?ISOQUINOLINE ALKALOIDS
?IPECAC
?BIOLOGICAL SOURCE: dried roots of cephalis ipecacuanha (brazilian / rio) Cephalis acuminata (panama / cartagena)
Family: rubiaceae
?Chemistry: Brazilian – emetine:cephalin ratio is 4:1
Panama – emetine:cephalin ratio is 1:1
?Uses: Expectorant in mild doses & as an emetic in large doses
Emetine also possesses anti protozoal activity
?PYRIDINE- PIPERIDINE ALKALOIDS
?TOBACCO
?BIOLOGICAL SOURCE: dried leaves of nicotiana tabacum
Family: solanaceae
?Chemistry: Nicotine, nornicotine & anabasine
?Use: Stimulant
?STEROIDAL ALKALOIDS
?KURCHI
?BIOLOGICAL SOURCE: dried bark of holarrhena antidysenterica
Family: apocynaceae
?Chemistry: Steroidal alkaloid conessine & norconessine
?Use: Amoebic dysentery
?ASHWAGANDHA
?BIOLOGICAL SOURCE: dried roots of withania somnifera
Family: solanaceae
?Chemistry:
2 types of chemical constituents
1⃣ steroidal lactones called withanolides like withaferine
2⃣ alkaloids like withanine, somniferine, anaferine. Also contains alcohols known as somnitol & somnirol
?Uses:
Sedative, hypnotic, hypotensive & immunomodulatory
?PYRAZOLINE ALKALOIDS
?PEPPER
?BIOLOGICAL SOURCE: dried fruits of piper nigrum
Family: piperaceae
?Chemistry: Alkaloid piperine is responsible for pungent taste aong with piperetine, resins, volatile oils containing limonene & pinen responsible for the odour
?Uses: Bronchitis & gonorrhoea
?PROTO ALKALOIDS
?EPHEDRA / MA HUANG
?BIOLOGICAL SOURCE: dried stem of ephedra gerardiana
Family: ephedreaceae / gnetaceae
?Chemistry: Contains amino alkaloids like ephedrine, norephedrine & pseudo ephedrine
Uses: Sympathomimetic & bronchodilator
?COLCHICUM / AUTUMN CROCUS
?BIOLOGICAL SOURCE: dried seeds & corms of colchicum luteum. Family: liliaceae
?Chemistry: Contains amino alkaloid colchicine & demecolchicine
?Uses: Rheumatism, treatment of gout, anti tumour activity & polyploidy
?ACONITE / BACHNAG
?BIOLOGICAL SOURCE: dried roots of aconitum napellus
Family: ranunculaceae
?Chemistry: Diterpene alkaloids such as aconitine, neopelline, neoline & small amount of ephedrine. Aconitine is an active constituent but if hydrolysed forms benzoyl aconine & aconine which are less active
?Uses: Externally in neuralgia & sciatica
?PSEUDO ALKALOIDS
?COFFEE
?BIOLOGICAL SOURCE: dried seeds of coffee Arabica
Family: rubiaceae
?Chemistry: Contains caffeine which is a salt of chlorogenic acid, volatile oil known as caffeol, enzymes & other phenolic compounds
?Uses: Stimulant, diuretic (due to theophylline), & source of caffeine
?Chemical Test:
1⃣ Murexide test: caffeine when heated with HCl & potassium chlorate gives a residue which turns purple when exposed to ammonia vapours
2⃣ Caffeine forms a white precipitate with tannin solution
?TEA
?BIOLOGICAL SOURCE: prepared leaves of thea sinensis
Family: theaceae
?Chemistry: Contains caffeine, theophylline, theobromine, oxidase enzyme & tannins
?Use: Stimulant, diuretic, source of caffeine
?Chemical Test: Murexide test
?KOLA NUTS / BISSY SEEDS
?BIOLOGICAL SOURCE: seeds of cola nitida
Family: sterculiaceae
?Chemistry: Contains caffeine, theobromine & a red pigment known as kola catechin
?Use: Stimulant
?COCOA SEEDS
?BIOLOGICAL SOURCE: seeds of theobroma cacao
Family: sterculiaceae
?Chemistry: Caffeine. Theobromine, other phenolic compounds
?Use: Stimulant
