Related entry: Castor oil
Castor oil seeds are obtained from Ricinus communis, Linn. (N.O. Euphorbiaceae), a native of India. The plant is cultivated in tropical and subtropical countries generally. Castor oil seeds are oblong and somewhat flattened, from 8 to 12 millimetres or more in length, with an arched dorsal surface, and nearly flat ventral surface. The thin, brittle, glossy seed-coat varies in colour from greyish-brown to grey, and is mottled with reddish-brown or black spots and stripes, thus differing from croton seeds, which are of a uniform, dull cinnamon-brown colour. At one extremity of the seed there is a prominent and usually pale-coloured caruncle, from which the raphe runs as a distinct line to the other extremity, where it terminates in a raised chalaza. A delicate, silvery-white membrane inside the seed-coat surrounds a large yellowish-white, oily endosperm, which encloses the embryo and two papery cotyledons. The fresh seeds have only a slight odour, and a sweetish, but slightly acrid taste, but they readily acquire a rancid odour.
Constituents.—The chief constituent of the seeds is about 50 per cent. of fixed oil (see Oleum Ricini); the crystalline alkaloid, ricinine, and the poisonous phytalbumose ricin, have been obtained from the cake left after extraction of the oil.
Action and Uses.—Castor oil seeds are poisonous, and two or three seeds have been known to prove fatal. Even so small a dose of ricin as 1/25 000 000 of the body weight may cause toxic symptoms when injected. The action of ricin is, however, much less powerful in the stomach than when injected hypodermically; in the latter case small doses soon produce immunity, anti-ricin being formed. The observation of this protective reaction laid the foundation of serum therapeutics.
The British Pharmaceutical Codex, 1911, was published by direction of the Council of the Pharmaceutical Society of Great Britain.