Yohimbe bark : its history and identification in commerce / by J. Small & F.M.J. Adams.

  • Small, J., active 1922.
Date:
[1922]
Catalogue details

Licence: In copyright

Credit: Yohimbe bark : its history and identification in commerce / by J. Small & F.M.J. Adams. Source: Wellcome Collection.

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    also given as follows:—“ The powdered bark is exhausted with diluted acetic acid, and the alkaloid is precipitated by means of sodium carbonate; the product is then dried and crystallised from alcohol.” The B.P.C. also gives the following:—“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 z per cent, to 1 per cent, strength, the anaesthesia lasting for one hour or more. Its effects are more persistent than those of tropa-cocaine. Yohimbine may be distinguished from cocaine in many ways, the latter being permanent in air and melting at 98° C. Yohim¬ bine 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 while strychnine in¬ creases all reflexes, yohimbine increases only the pelvic reflexes. Yohimbine also exerts an anaesthetic action upon sensory nerve terminations. It lowers blood pressure by dilating the vessels; this action is exerted on the walls of the vessels themselves, and affects most vessels, such as those of the skin, kidneys, intes¬ tines, and external genital organs. It increases depth and fre¬ quency of respiration. Poisonous doses paralyse respiration. It has been used 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 the hydro¬ chloride. The dose is usually 3-8 Mgms. (1-20 to 1-8 grain). ’ It is of interest to note that a liquid preparation for veterinary use, sold under the trade name “ Yohimbine Schmidt,” was shown by Robert14 in 1912 to be a preparation of veratrine (cevadine), not of yohimbe bark. Botanical.—In 1902, Schumann21 identified the bark as that of Corynanthe Yohimbe, from Kribi, in the Cameroons, and dis¬ tinguished the species from others of the same genus by the winged tails of the corolla lobes. The bark he describes as being from 8-10 Mm. thick, with an external corky layer of a grey- brown colour, covered with isolated lichens, and showing longi¬ tudinal and transverse fissures like old cinchona. The trans¬ verse fracture he describes as of an uniform yellow-brown colour, with a short, soft fibrous surface like rough velvet. Under the microscope the structure much resembles that of Cinchona, but differs in the arrangement of the bast fibres of the secondary bark in definite long radial rows. In 1904, Herzog11 examined a substituted false bark, that of Corynanthe macroceras, and stated that this bark contains little yohimbine and larger quantities of totally inert alkaloids, which are closely allied to the active yohimbine. This was an impor¬ tant discovery, as this species closely resembles other barks from the same region—i.e., the Cameroons—which yield the drug of medicinal and commercial value. The taxonomic position of this and the species yielding the genuine bark was changed in the following year, and the name Pausinystalia replaced Corynanthe (in part). This was done by Beille and Dupony. In 1906, Beille3, in collaboration with Professor Dupony, made a pharmacological study of a bark said to have aphrodisiac and anaesthetic properties imported from the French Congo, and known to r,he natives by the name “Eudun.” This new species was described as Pausinystalia Triltesii, and placed with the other two already known in the new genus Pausinystalia. The two genera Pausinystalia and Corynanthe are distin¬ guished by Beille and Dupony by the following morphological and anatomical characters :—