Wikipedia
Corynanthine, also known as rauhimbine, is an alkaloid found in the Rauwolfia and Pausinystalia (formerly known as Corynanthe) genera of plants. It is one of the two diastereoisomers of yohimbine, the other being rauwolscine. It is also related to ajmalicine.
Corynanthine acts as an α-adrenergic and α-adrenergic receptor antagonist with approximately 10-fold selectivity for the former site over the latter. This is in contrast to yohimbine and rauwolscine which have around 30-fold higher affinity for α-adrenergic over α-adrenergic. 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.