A. Yohimbine
Synonyms Quebrachine; Corynine; Aphrodine;
Biological Sources It is found in the root bark of Alchornea floribunda Muell. Arg. (Euphorbiaceae) (Niando); plant* of Catharanthus lanceus Pichon (Boj.) (Apocyraceae) (Lanceleaf Periwinkle); bark of Pausinystalia johimbe (K. Schum.) (Rubiaceae) (Yohimbe); root of Rauvolfia serpentina (L.) Benth. (Apocynaceae) (Rauvolfia, Chandra, Sarpaganda); and plant of Rauvolfia tetraphylla L. (Apocynaceae) (Pinque-Pinque).
Chemical Structure
(16a, 17a)-17-Hydroxyyohimban-16-carboxylic acid methyl ester; (C21H26N2O3).
Characteristic Features
1. It is obtained as orthorhombic needles from dilute alcohol having mp 234°C.
2. Its specific optical rotations are: [α]20D + 50.9° to + 62.2° (ethanol); [α]20D + 108° (pyridine); and [α]20546 + 129° (C = 0.5 in pyridine).
3. It has uvmax (methanol): 226, 280, 291 nm (log ε 4.56, 3.88, 3.80).
4. It is freely soluble in ethanol, chloroform, hot benzene; moderately soluble in ether; and sparingly soluble in water.
Identification Tests
Yohimbine Hydrochloride (C21H26N2O3.HCl) (Aphrodyne, Yocon, Yohimex, Yohydrol): It is obtained as orthorhombic plates or prisms from ethanol which decompose at 302°C. Its specific optical rotation [α]22D + 105° (water). It is found to be soluble in nearly 120 ml water, 400 ml ethanol, and the aqueous solution is almost neutral.
Uses
1. It is an aderenergic blocking agent, which has been used extensively in angina pectoris and arteriosclerosis.
2. It has been used successfully for the treatment of impotency in patients with vascular or diabetic problems.
3. It is invariably employed as a pharmaiological probe for the study of α2-adrenoreceptor.
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* Emboden reported that this plant contains upto 5% yohimbin.
