C23H82N2O4 = 400.276.
Corynine, C23H32N2O4, is an alkaloid obtained from yohimbehe or yumbehoa bark, Corynanthe Yohimbi, Schum. (N.O. Rubiaceae), a plant growing near Kribi, in the southern district of the Cameroons. It is also known under the trade-names Yohimbine and Aphrodine. Yohimbi bark contains from 0.3 to 1.5 per cent. of alkaloidal matter, including corynine (yohimbine), corynanthine (yohimbenine), and at least two other alkaloids, but the active aphrodisiac is corynine (yohimbine). Corynanthine or yohinbenine (melting-point, 105° to 106°) is more readily soluble in ether than the other alkaloids, corynine (yohimbine) and one other being only sparingly soluble, while the fourth is insoluble in ether and only sparingly soluble in absolute alcohol or chloroform. False yohimbi bark, from C. macroceras, K. Schum, contains corynanthine (yohimbenine) chiefly. Corynine may be obtained by exhausting the powdered bark with diluted acetic acid and precipitating the solution thus obtained by means of sodium carbonate. The product is dried, and crystallised from alcohol. Corynine occurs in the form of white prismatic needles, or as a white amorphous powder, becoming yellow, finally orange-red, on exposure to light, and having a weak odour of benzaldehyde. Its solutions are affected by exposure to light in the same way as the solid substance. Melting-point, 231° to 234°. On long heating at 120° to 130° it splits up into water and corynine anhydride. It is a tertiary base, optically inactive, and has certain properties in common with cocaine, its hydrochloride acting as an anaesthetic when applied to the cornea in solution of ¼ to 1 per cent. strength, the anaesthesia lasting for an hour or so. Its effects are more persistent than those of tropacocaine. Corynine may be distinguished from cocaine in many ways, the latter being permanent in air and melting at 98°. When cocaine is treated with fuming nitric acid and then with alcoholic potash solution it gives no colour reaction, but corynine becomes first deep green and then yellowish with nitric acid, and, on the addition of alcoholic potash, cherry-red. Cocaine remains colourless when dissolved in strong sulphuric acid and then treated with chlorinated lime, whilst corynine gives an intense orange-red colouration. The former blackens calomel by reduction, the latter does not. In contact with alkalies corynine is coloured orange yellow. It dissolves without colouration in concentrated sulphuric acid. If this solution be treated with potassium bichromate, in the same way as strychnine, it yields streaks with blue-violet edges, which gradually become dirty green. Its solution in concentrated hydrochloric acid is at first colourless, but soon becomes intensely yellow. If a little of the alkaloid be dissolved in 50 per cent. sulphuric acid and a few grains of cane sugar be added, the solution on being warmed in a porcelain capsule on a water-bath will develop a wine-red colour.
Almost insoluble in water; soluble in alcohol, methyl alcohol, acetone, or chloroform; slightly soluble in ether, or benzene.
Action and Uses.—Corynine is employed hypodermically or by the mouth as a sexual stimulant in impotence; its action as an aphrodisiac is said to be superior to that of strychnine, in that, whilst strychnine increases all reflexes, corynine only increases the pelvic reflexes. Corynine exerts an anaesthetic action upon sensory nerve terminations. It lowers blood pressure by dilating vessels; this action is exerted upon the walls of the vessels themselves, and affects most vessels, such as those of the skin, kidney, intestines and external genital organs. It increases the depth and frequency of respiration. Poisonous doses paralyse respiration. It has been used in ¼ to 1 per cent. solution as a local anaesthetic for the eye in place of cocaine. It produces no mydriasis, and does not affect the corneal epithelium. It is chiefly used in the form of hydrochloride.
Dose.—3 to 8 milligrams (1/20 to ⅛ grain).