QUININE

QUININE

Most of the quinine is obtained from the bark of Cinchona ledgeriana and its hybrids (C. officinalis) (Family Rubiaceae) which contains about 8% quinine. Cinchona trees grow wildly in South America and are cultivated in Java. The powdered bark is mixed with sodium hydroxide solution and slaked lime, and the liberated alkaloids are extracted with hot petroleum. The extract is separated and shaken with the required quantity of hot, very diluted sulphuric acid. The alkaloids pass into the aqueous layer as sulphates. The separated aqueous solution is cooled, and the sparingly soluble quinine sulphate crystallizes.

The pure quinine, m.p. 177, crystallizes as colourless needles with 3 molecules of water of crystallization. It is efflorescent, losing 1 molecule of water at 20° under normal conditions and losing 2 molecules in a dry atmosphere.

Quinine occurs as a laevorotatory, odourless, white crystalline powder possessing an intensely bitter taste. One gram dissolves in 1900 ml water, 760 ml boiling water, 0.8 ml alcohol, 80 ml benzene, 1.2 ml chloroform, and 250 ml dry ether; almost insoluble in petroleum ether. It is stored in well-closed containers and protected from light.

It behaves as a diacidic base and forms salts with two equivalents of an acid. The salts are of two types. The acid ordiacid salts and the neutral salts. The neutral salts are formed by involvement of only tertiary nitrogen in the quinuclidine nucleus. When both basic nitrogens are involved, the acid salts are formed. The quinoline nitrogen is very much less basic than the quinuclidine nitrogen. The mono-acid salts of quinine are generally much less soluble in water than the di-acid salts.

On oxidation with chromic acid quinineis is decomposed to form quininic acid.

Test for quinine : To about 20 ml of a quinine salt solution (1 in 1000), bromine water (0.25 ml) N

was added, shaken well and then dilute ammonia Solution was mixed. A bright green colour is formed.