Alkaloids
Author: Unkown
Description: Some comprehensive notes taken in the lecture of alkaloids. Contains drugs of the following classes- Indole Alkaloids (Ergot, Vinca, Nux vomica, Rauwolfia), Tropane Alkaloids (Belladonna, Stramonium, Coca Leaves), Quinazoline Alkaloids (Vasaka Leaf / Adulsa), Pyridine Alkaloids (Lobelia Herb), Imidazole Alkaloids (Pilocarpus), additional Indole Alkaloids (Calabar Beans, Opium Poppy Plant), Quinoline Alkaloids (Cinchona Bark), Isoquinoline Alkaloids (Ipecac), Pyridine - Piperidine Alkaloids (Tobacco), Proto Alkaloids (Ephedra, Colchicum, Aconite), Pseudo Alkaloids (Coffee, Tea, Kola Nuts / Bissy Seeds, Cocoa Seeds), Steroidal Alkaloids (Kurchi, Ashwagandha), Pyrazoline Alkaloids (Pepper).
Number of Pages: 14 pages |
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ALKALOIDS
Author: unknown
Alkaloids are basic nitrogen containing compounds obtained from plants, animals & microorganisms having a marked physiological action
Characteristics:
Well defined crystalline substances, generally occurring as solids except nicotine which is a liquid, colourless except berberine which is a yellow coloured alkaloid. Occur in plants in the salt form.
They answer the following chemical tests:
1. mayer’s reagent- (potassium mercuric iodide)
cream coloured precipitate
2. wagner’s reagent- (iodine in potassium iodide)
reddish brown precipitate
3. hager’s reagent- (salt solution of picric acid)
yellow precipitate
4. dragendorf’s reagent- (potassium bismuth iodide)
reddish brown precipitate
Caffeine is a pseudo alkaloid drug which does not answer this test
Extraction: The powdered drug is defatted using petroleum ether if necessary
The powder is further basified using lime to break the salt form of the alkaloid & liberate free base which can be extracted using an organic solvent
Alkaloidal salts can be directly extracted using an acidified aqueous solvent
Classification:
1. pharmacological method
2. taxonomic method
3. biosynthetic method
4. chemical method – true & proto alkaloids
1. Pyrrole & pyrrolidine eg- coca
2. pyridine & piperidine eg- coniine
3. tropane eg- atropine
4. quinoline eg- cinchona
5. indole eg- rauwolfia
6. purine eg- caffeine
7. steroidal eg- kurchi
8. isoquinoline eg- opium
eg- ephedrine
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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)
GEOGRAPHICAL SOURCE: Switzerland
Known to have caused gangrene (ergotism) in germany
Life cycle:
1. sexual / sphacelial stage
2. asexual / schlerotium stage
Sexual stage:
The ascospores infect the ovary of the rye plant & if conditions are favourable it develops hyphal strands
It forms a white mass over the ovary known as the mycelium
Asexual stage:
The hyphal strands further develop invading the ovary & converting it to a hard violet schlerotium
Schlerotium contains stromatum which shows a globular stalk
It encloses bag like structures known as ascus containing ascospores
If these ascospores are liberated they infect another rye plant
Morphology of schlerotium:
Hard, violet, odourless, with an unpleasant taste
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:
1. gives a blue colour with Van Curk’s reagent (para dimethyl amino benzaldehyde)
2. gives blue fluorescence in water
3. when treated with ether, H2SO4 followed by sodium bicarbonate, aqueous layer shows a red violet colour
4. ergotamine + glacial acetic acid + ethyl acetate + H2SO4 gives a blue solution with a red tinge. When further treated with FeCl3 the blue colour disappears
VINCA / PERIWINKLE
BIOLOGICAL SOURCE: aerial parts of catharanthus roseus
Family: apocynaceae
GEOGRAPHICAL SOURCE: India, Madagascar
Morphology:
Leaves are small, opaque, dark green, odourless & bitter to taste
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
GEOGRAPHICAL SOURCE: srilanka, India
Morphology:
Seeds are circular, flat, grayish green, covered with trichomes & extremely bitter to taste
Chemistry:
Contains two main indole alkaloids strychnine & brucine
Use:
Rarely used as a nerve tonic as it is poisonous in large doses
Chemical Test:
1. section when treated with concentrated HNO3 shows a yellow colour with brucine
2. section when treated with ammonium vanadate & H2SO4 shows a purple colour with strychnine
3. strychnine when treated with H2SO4 & K2Cr2O7 develops a violet to yellow colour
RAUWOLFIA / SARPAGANDHA
BIOLOGICAL SOURCE: dried roots of rauwolfia serpentina
Family: apocynaceae
GEOGRAPHICAL SOURCE: asia, America
Morphology:
Snake shaped, brown coloured, longitudinal wrinkles tapering towards the end
Chemistry:
Reserpine, ajamlicine, serpentine
Use:
Antihypertensive by preventing uptake of adrenaline
Chemical Test:
1. freshly fractured surface of the root when treated with concentrated HNO3 shows red coloured medullary rays
2. reserpine gives a violet colour with vanillin in acetic acid
TROPANE ALKALOIDS
BELLADONA
BIOLOGICAL SOURCE: dried leaves of atropa belladonna
Family: solanaceae
GEOGRAPHICAL SOURCE: England, Europe, India
Morphology:
Leaves are greenish brown, ovate in shape with an entire margin & bitter to taste
Microscopic Characters:
Dorsiventral leaf
Collenchyma above & below the mid rib
Unicellular covering trichomes, unicellular glandular trichomes
Microsphaenoidal calcium oxalate crystals
Chemistry:
Atropine, hyoscyanine, belladonine
Use:
Atropine is a parasympatholytic, thus decreases secretion & spasms
Chemical Test:
Vitali morin test – to the drug fuming nitric acid is added & it is evaporated to dryness.
Methanolic 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
GEOGRAPHICAL SOURCE: America, france
Morphology:
Leaves are grayish green with a crenate margin & unequal base
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
GEOGRAPHICAL SOURCE: Bolivia, peru
Morphology:
Peruvian leaves are pale green, fragile, thin, elliptical in shape
Bolivian leaves are greenish brown, oval in a shape with a prominent mid rib
Microscopic Characters:
Dorsiventral leaf
Collenchyma above & below mid rib
Xylem surrounded by phloem & pericyclic fibres
Paracytic stomata
Chemistry:
Cocaine, cinnamoyl cocaine, tropocaine, benzoylecgonine
Extraction:
The leaf powder is basified with lime & extracted using an organic solvent
The free bases are converted to their hydrohlorides by using HCl
Due to this procedure cocaine liberates ecgonine, methanol & benzoic acid whereas cinnamoyl cocaine generates ecgonine, methanol & cinnamic acid
The ecgonine thus obtained is used to synthesize cocaine by treating it with benzoic anhydride, methyl iodide, methanol & sodium methoxide
Use:
Local anaesthetic
Chemical Test:
Drug powder when heated with concentrated H2SO4 gives a typical odour of methyl benzoate
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QUINAZOLINE ALKALOIDS
VASAKA LEAF / ADULSA
BIOLOGICAL SOURCE: dried & fresh leaves of adhatoda vasica
Family: acanthaceae
GEOGRAPHICAL SOURCE: India
Morphology:
Leaves are dark green, lanceolate in shape, have a crenate margin with a characteristic odour & bitter taste
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
GEOGRAPHICAL SOURCE: India
Morphology:
Leaves are sessile, large, dark green & possess an acrid taste
Chemistry:
Lobeline, lobelidine & isolobanine
Use:
Respiratory stimulant
Chemical Test:
1. lobeline solution if heated gives typical odour of acetophenone
2. lobeline in H2SO4 when treated with formaldehyde develops red colour
IMIDAZOLE ALKALOIDS
PILOCARPUS
BIOLOGICAL SOURCE: dried leaves of pilocarpus jaborandi
Pilocarpus microphyllus
Family: rutaceae
GEOGRAPHICAL SOURCE: south America
Morphology:
Leaves are greyish green with an asymmetrical base & possesses aromatic odour & bitter taste
Chemistry:
Contains pilocarpine, pseudopilocarpine, pilosine & limonene
Uses:
Antagonist to atropine, causes miosis, increases salivation & sweating
Chemical Test:
Pilocarpine solution when treated with H2SO4, H2O2, benzene & K2Cr2O4, the organic layer appears bluish violet in colour whereas aqueous layer shows yellow colour
INDOLE ALKALOIDS
CALABAR BEANS
BIOLOGICAL SOURCE: dried type seeds of physostigma venenosum
Family: leguminosae
GEOGRAPHICAL SOURCE: Africa
Morphology:
Reddish brown in colour, hard, shiny & rough to touch
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
GEOGRAPHICAL SOURCE: India (MP), turkey, Pakistan, Afghanistan
Collection:
Collection is started when capsules change colour from dark green to yellowish green.
Longitudinal incisions about 2mm deep are given on the capsules to exude the latex
The latex is allowed to solidify overnight & later scraped off
The process is repeated 4 times with a gap of 2 days
Morphology:
The dried latex is dark brown, extremely bitter to taste & has a strong odour
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
Chemical Test:
1. aqueous solution of meconic acid shows a deep reddish purple colour with ferric chloride
2. morphine when sprinkled with concentrated HNO3 shows an orange red colour. This is not allowed by codeine
3. morphine solution when treated with ferric chloride & potassium ferricyanide gives a bluish green colour
4. papaverine solution in HCl & potassium ferricyanide develops a lemon yellow colour
Varieties of opium:
Indian, Turkish, Persian, European, manipulated Persian & European
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QUINOLINE AKALOIDS
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
GEOGRAPHICAL SOURCE: India, Bolivia, srilanka
Collection:
It is collected by coppicing method
Vertical incisions are made on branches, trunk of the tree & these incisions are connected by horizontal circles
The bark is then stripped off & dried in sunlight & further by artificial heat (175 degree F)
The root bark is collected by uprooting trees & separating manually
Morphology:
Stem bark is rough with transverse fissures
Outer surface is grey & inner surface is pale yellowish brown to deep reddish brown
Root bark is curved, outer surface is scaly, outer & inner surface with same colour
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:
1. on heating the drug in a dry test tube with glacial acetic acid, purple vapours are produced
2. thalleoquin test: drug + bromine water + dilute ammonia gives an emerald green colour
3. drug 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
ISOQUINOLINE ALKALOIDS
IPECAC
BIOLOGICAL SOURCE: dried roots of cephalis ipecacuanha (brazilian / rio)
Cephalis acuminata (panama / cartagena)
Family: rubiaceae
GEOGRAPHICAL SOURCE: brazil, panama
Morphology:
Brazilian ipecac is dark brick red as compared to greyish brown panama ipecae
Both possess faint odour & bitter taste
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
Chemical Test:
1. emetine shows a bright green colour with H2SO4 & molybdic acid
2. emetine when shaken with water & small amount of HCl, filtered & to the filtrate potassium chlorate is added gives a yellow colour changing to red
PYRIDINE- PIPERIDINE ALKALOIDS
TOBACCO
BIOLOGICAL SOURCE: dried leaves of nicotiana tabacum
Family: solanaceae
GEOGRAPHICAL SOURCE: India, france
Morphology:
Leaves are large, green with a dentate margin
It has a characteristic strong odour & bitter taste
Chemistry:
Nicotine, nornicotine & anabasine
Use:
Stimulant
PROTO ALKALOIDS
EPHEDRA / MA HUANG
BIOLOGICAL SOURCE: dried stem of ephedra gerardiana
Family: ephedreaceae / gnetaceae
GEOGRAPHICAL SOURCE: china, Pakistan
Morphology:
Greyish green, thin, cylindrical stem bearing scaly leaves & internodes
No typical odour but has a bitter taste
Chemistry:
Contains amino alkaloids like ephedrine, norephedrine & pseudo ephedrine
Uses:
Sympathomimetic & bronchodilator
Chemical Test:
Aqueous solution of ephedrine shows a violet colour when treated with dilute HCl & CuSO4 followed by dilute NaOH
COLCHICUM / AUTUMN CROCUS
BIOLOGICAL SOURCE: dried seeds & corms of colchicum luteum
Family: liliaceae
GEOGRAPHICAL SOURCE: Europe
Morphology:
Seeds are hard, reddish brown, rough to touch whereas corms are yellowish in colour with a longitudinal groove & bitter to taste
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
GEOGRAPHICAL SOURCE: germany, spain
Morphology:
Roots are dark brown, longitudinally wrinkled & tapering towards one end
They have slight odour & taste
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
For more notes, animations and softwares visit http://www.pharmaxchange.info
PSEUDO ALKALOIDS
COFFEE
BIOLOGICAL SOURCE: dried seeds of coffee Arabica
Family: rubiaceae
GEOGRAPHICAL SOURCE: southern part of India, Indonesia
Collection:
The unripe coffee fruit is dark green & is collected when it turns red
Each fruit has two locules containing one seed each
The seeds are separated, roasted because of which they develop a dark brown colour & a typical odour
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:
1. Murexide test: caffeine when heated with HCl & potassium chlorate gives
a residue which turns purple when exposed to ammonia vapours
2. Caffeine forms a white precipitate with tannin solution
TEA
BIOLOGICAL SOURCE: prepared leaves of thea sinensis
Family: theaceae
GEOGRAPHICAL SOURCE: India, srilanka
Collection:
The tea plant is a small green shrub wherein younger leaves are picked & allowed to undergo fermentation
Polyphenol oxidase carries out oxidation to produce furfural & other phenolic compounds
The process imparts a dark brown or black colour & a typical odour of tea powder
For preparation of green tea, fresh leaves are dried & roasted in copper pans & finally powdered
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
GEOGRAPHICAL SOURCE: west Africa, brazil
Morphology:
Seeds are plano convex in shape & reddish brown with a bitter taste
Chemistry:
Contains caffeine, theobromine & a red pigment known as kola catechin
Use:
Stimulant
COCOA SEEDS
BIOLOGICAL SOURCE: seeds of theobroma cacao
Family: sterculiaceae
Collection:
The fruits are ellipsoidal in shape with a white pulp & contain about 40 to 50 seeds
Fermentation is carried out in boxes for about 3 days at a temperature below 60 degree Celsius
The seeds acquire a different coulour, taste & odour
Seeds are then roasted to evaporate the water
It also facilitates removal of the seed coat
Seeds are then powdered to obtain cocoa powder
Chemistry:
Caffeine. Theobromine, other phenolic compounds
Use:
Stimulant
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STEROIDAL ALKALOIDS
KURCHI
BIOLOGICAL SOURCE: dried bark of holarrhena antidysenterica
Family: apocynaceae
GEOGRAPHICAL SOURCE: India
Chemistry:
Steroidal alkaloid conessine & norconessine
Use:
Amoebic dysentery
ASHWAGANDHA
BIOLOGICAL SOURCE: dried roots of withania somnifera
Family: solanaceae
GEOGRAPHICAL SOURCE: India, Afghanistan
Morphology:
Roots are cylindrical, buff coloured, have a characteristic odour & are tasteless
Microscopic Characters:
Outermost layer of cork cells followed by cortex
Vascular bundle consists of phloem parenchyma & xylem blocking the pith
Chemistry:
2 types of chemical constituents
1. steroidal lactones called withanolides like withaferine
2. 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
GEOGRAPHICAL SOURCE: south India, Indonesia
Morphology:
Fruits are green when unripe but turn dark black after drying
The dried fruits are wrinkled with an aromatic odour & pungent taste
Chemistry:
Alkaloid piperine is responsible for pungent taste aong with piperetine, resins, volatile oils containing limonene & pinen responsible for the odour
Uses:
Bronchitis & gonorrhoea
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