B. Cinchonine
Biological Sources It occurs in most varieties of cinchona bark as mentioned under quinine (section ‘A’). Besides, cinchonine especially occurs in the bark of Cinchona micrantha R & P. belonging to the natural order Rubiaceae.
Chemical Structure
(9S) - Cinchonan-9-ol; (C19H22N2O)
Isolation The detailed method of isolation has been given under quinine (section ‘A’). Besides, Rabe* has put forward another method of isolation of cinchonine.
Characteristic Features
1. Cinchonine is obtained as needles from ethanol or ether having mp 265°C.
2. It begins to sublime at 220°C.
3. Its specific optical rotation is [α]D + 229° (in ethanol).
4. Solubility Profile: 1g dissolves in 60 ml ethanol, 25 ml boiling ethanol, 110 ml chloroform, 500 ml ether; and practically insoluble in water.
5. It has two distinct dissociation constants: pK1 5.85 and pK2 9.92.
Identification Tests Cinchonine may be identified by forming its specific derivatives, namely:
1. Cinchonine Hydrochloride Dihydrate (C19H22N2O.HCl.2H2O): It is obtained as fine crystals. The mp of its anhydrous salt is 215 °C with decomposition. 1g dissolves in 20 ml water, 3.5 ml boiling water 1.5 ml alcohol, 20 ml chloroform; and slightly soluble in ether. The aqueous solution is almost neutral.
2. Cinchonine Dihydrochloride (C9H22N2O.2HCl): It is usually obtained as white or faintly yellow crystals or crystalline powder. It is found to be freely soluble in water or ethanol.
3. Cinchonine Sulphate Dihydrate [(C19H22N2O)2.H2SO4.2H2O]: It is commonly obtained as lustrous extremely bitter crystals. Its anhydrous salt has mp 198°C. 1g dissolves in 65 ml water, 30 ml hot water, 12.5 ml ethanol, 7 ml hot ethanol, 47 ml chloroform; and slightly soluble in ether. The aqueous solution is practically neutral.
4. Epicinchonine [Synonyms (9R)-Cinchonan-9-ol]: It has mp 83°C; and [α]22D + 120.3° (C =0.806 in ethanol).
Uses
1. It is used as an antimalarial agent.
2. It is employed as a tonic in waters, bitters and liqueurs.
3. It is broadly used for febrifuge, schizonticide, stomachic, amebiasis, dysentry, flu, fever, and as
a mild stimulant of gastric mucosa.
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* Rabe, Ber. 41, 63 (1908)
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