Indole alkaloids Flashcards
What are alkaloids?
Alkaloids are heterocyclic nitrogenous compounds of plant origin that are physiologically active
What are indole alkaloids?
Indole alkaloids are derived from tryptophan and they contain an indole ring which is a bicyclic structure comprising of a benzene ring fused to a five membered nitrogen containing pyrrole ring
What are some important drugs of indole alkaloids and their active alkaloids?
- Rauwolfia: Reserpine
- Ergot: Ergotamine, ergometrine
- Nux Vomica: Strychnine, brucine
- Physostigma: Physostigmine
- Catharanthus: Vincristine, vinblastine
What is Rauwolfia?
Rauwolfia is the dried root of Rauwolfia serpentina, in honor of Dr. Rauwolf and because of its snake like roots
Family of Rauwolfia
Apocyanaceae
What are the constituents of Rauwolfia?
Contains not less than 0.15% and not more than 0.20% alkaloids calculated as reserpine.
1. Reserpine
2. Rescinnamine
3. Deserpine
What are the qualities of Reserpine?
It comprises of white to pale yellow, colorless, crystalline powder that darkens slowly in sunlight and rapidly in solution
Deserpine
It is obtained from Rauwolfia canescens
Extraction of reserpine
- Grinding of rauwolfia
- Extraction with methanol
- Concentration of methanol by distilling of solvent
- Mixing with water
- Washing with chlorinated solvent to remove impurities
- Alkaloid is obtained
Uses of reserpine
Anti-hypertensive, sedative
What is ergot?
ergot is obtained from the dried sclerotium of Claviceps purpurea. It is also know as ergot of rye
Historical significance of ergot
It contaminated rye fields and caused gangrene in extremities and convulsion which were known as St. Anthony’s Fire. It was known to cause disease in cattle and human which was known as ergotism. Produced convulsions and gangrene.
Macroscopy of ergot
- Externally: Violet to black
- Internally: white
- Odor: Characteristic
- Taste: Unpleasant
- Shape: Fusiform or slightly curved
Active constituents of ergot
Alkaloids may be water soluble or water insoluble:
1. Water soluble: Ergonovine
2. Water insoluble: Ergotamine, Ergotaxine
Synthetically prepared too. They are all derivatives of lysergic acid
Uses of ergot
- rich source of alkaloids
- used in migraines
- used to stimulate labor
- as an abortifacient and to reduce post partum hemorrhage
Extraction of ergotamine
- Parasitic source
- Saprophytic source
What is Nux Vomica?
Nux vomica is the dried, ripe seed of Strychnos Nux vomica.
What are the macroscopic characteristics of Nux Vomica?
It is a relatively small tree, only 12 m in height, found in Sri Lanka. It consists of fruits with 3-5 seeds.
Constituents of Nux Vomica
1.5-5 % alkaloids strychnine and brucine. Strychnine is located near the center of the seeds and brucine in the outer epirdermis
Extraction of nux vomica
Extracted with sulfuric acid, solvent is concentrated and precipitated by lime, separated by means of solvent and purified by recrystallization
Uses of nux vomica
source of strychnine and brucine
strychnine is used as vermin killer
brucine is less toxic and used commercially as alcohol denaturant
strychnine is used as central stimulant
What is physostigmine?
Physostigmine is the dried, ripe fruit of Physostigma venenosum, yielding not less than 0.15% alkaloids
Active constituents of physostigmine?
Contains many alkaloids but the major one is Physostigmine, contained in cotyledons from 0.04 to 0.3%
Macroscopic characteristics of physostigmine
white color, odorless and may acquire a red tint on contact with sunlight, air or water or in contact with minerals
Uses of physostigmine
Used for glaucome treatment, is cholinesterase inhibitor and is used to contract ciliary muscles and reduce intraocular pressure
What is catharanthus?
Catharanthus (aka vinca, madagascar periwinkle and bright eyes) is the dired, whole plant of Cantharanthus roseus
Family of catharanthus
Apocynaceae
Constituents of catharanthus
more than 70 alkaloids
indole-indoline alkaloids serpentine, locherine, ajmalacine, tetrahydroalstonine
demric indole alkaloids like vincristine, vinblastine, vinrosidine
Extraction
aqueous extraction of ground tissue
extraction with organic solvent e.g ethyl acetate
Uses
used as remedy for type-2 diabetes, anti-cancer effects by arresting cell division at metaphase and for ornamental purposes
