Page 118 - Medicinal Plants_PharmD general

Chromatographic identification of alkaloids:

Thin layer chromatographic technique is used for identification of
the alkaloidal constituents of drugs. TLC can be performed on silica gel or
alumina. Silica is the most active stationary phase; good separations are
achieved even when low concentrations of the alkaloids are applied.
The solvent system: Numbers of solvent systems are used depending on
the nature of the alkaloids to be separated e.g. Benzene-ether-diethylamine
(40:24:10) for Cinchona alkaloids and toluene:acetone:alcohol: ammonia
(45:45:7:3) for opium alkaloids.
Visualisation of the alkaloids: Many alkaloids can be seen on the
chromatogram in day light (coloured alkaloids). A large number of
alkaloids yield typical fluorescence colours in UV light. The reagent most
commonly used for detecting alkaloids is the Dragendorff’s reagent which
give an orange colour with most of the alkaloids.

Drugs containing alkaloids
Alkaloids show great variety in their botanical origin, in chemical

structure and in pharmacological action, the following are some alkaloid-
containing drugs:
Opium: morphine, codeine, thebaine narceine, papaverine.
Cinchona bark: Quinine, quinidine, cinchonine, cinchonidine
Nux vomica seeds: strychnine, brucine, vomicine
Colchicum seed: Colchicine, demecolcine
Calabar bean: physostigmine (eserine), isophysostigmine ,calabatine,
calabacine
Belladonna leaves: Hyoscyamine, hyoscine, atropine
Coca leaves: Cocaine, cinnamyl cocaine, -truxilline
Jaborandi leaf: pilocarpine, isopilocarpine, pilosine and isopilosine
Tea leaves: caffeine

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