Title: Corynanthine
CAS Registry Number: 483-10-3
CAS Name: (16b,17a)-17-Hydroxyyohimban-16-carboxylic acid methyl ester
Additional Names: rauhimbine
Molecular Formula: C21H26N2O3
Molecular Weight: 354.44
Percent Composition: C 71.16%, H 7.39%, N 7.90%, O 13.54%
Literature References: From bark of Pseudocinchona africana Chev., Corynanthe johimbe K. Schum., Rubiaceae and Rauwolfia serpentina (L.) Benth., Apocynaceae: Raymond-Hamet, Compt. Rend. 212, 305 (1941); Jorio, Ann. Chim. Farm. 1939, 50, C.A. 33, 93069 (1939); Le Hir et al., Ann. Pharm. Fr. 11, 546 (1953); Hofmann, Helv. Chim. Acta 37, 314 (1954). Identity with rauhimbine: idem, ibid. 849. Structure and stereochemistry: Janot et al., Bull. Soc. Chim. Fr. 1952, 1085; 1961, 637.
Properties: Stout prisms from acetone, dec 225-226°. [a]D19 -85° (c = 0.5 in pyridine). uv max (methanol): 226, 283, 290 nm (log e 4.56, 3.87, 3.79). Practically insol in water or petr ether. Sol in 40 parts of boiling chloroform, in 60 parts of boiling benzene, in 20 parts of boiling ethyl acetate, in 5 parts of boiling alcohol.
Optical Rotation: [a]D19 -85° (c = 0.5 in pyridine)
Absorption maximum: uv max (methanol): 226, 283, 290 nm (log e 4.56, 3.87, 3.79)
Derivative Type: O,N-Dibutyrylcorynanthine hydrochloride
Literature References: Prepn: Reiser et al., US 2975183 (1961 to Chemische Werke Albert).
Properties: Crystals from benzene, mp 208-210°.
Melting point: mp 208-210°
Derivative Type: O,N-Dipropionylcorynanthine hydrochloride
Literature References: Prepn: Reiser et al., loc. cit.
Properties: Crystals from isopropanol, mp 236-237°.
Melting point: mp 236-237°
Corypalmine Corytuberine Cotarnine Cotinine Cotoin

Systematic (IUPAC) name
(16β,17α)-17-hydroxy-yohimban-16-carboxylic acid methyl ester
Clinical data
Legal status Uncontrolled
Routes Oral
CAS number 483-10-3
ATC code None
PubChem CID 92766
ChemSpider 83744
Chemical data
Formula C21H26N2O3 
Mol. mass 354.44 g/mol

Corynanthine, also known as rauhimbine, is an alkaloid found in the Rauwolfia and Pausinystalia (formerly known as Corynanthe) genera of plants.[1][2] It is one of the two diastereoisomers of yohimbine, the other being rauwolscine.[3][4] It is also related to ajmalicine.

Corynanthine acts as an α1-adrenergic and α2-adrenergic receptor antagonist with approximately 10-fold selectivity for the former site over the latter.[3][4] This is in contrast to yohimbine and rauwolscine which have around 30-fold higher affinity for α2-adrenergic over α1-adrenergic.[3][4] As a result, corynanthine is not a stimulant (or an aphrodisiac for that matter), but a depressant, and likely plays a role in the antihypertensive properties of Rauwolfia extracts. Like yohimbine and rauwolscine, corynanthine has also been shown to possess some activity at serotonin receptors.[5]