Hypotensive effect of Baissea axillaris (Apocynaceae) leaves in normotensive rabbits

Baissea axillaris leaves are used in ethnomedicine to reduce elevated blood pressure. The effect of the aqueous extract of the leaves (obtained by decoction method) on blood pressure was tested on normotensive rabbits intravenously (i.v.) at doses of 2.5, 5, 10, and 20 mg/kg. The probable mechanism of action of the extract was examined by prior administration of atropine (0.5mg/kg i.v.) or promethazine (0.25mg/kg i.v.) followed by administration of the water extract . The effects of chloroform fraction was tested at tested at 0.625,1.25, 2.5mg/kg while the n-butanol fraction was tested at 2.5,5,10, 25, 50,and 100mg/kg dose points. The aqueous extract showed a dose-dependent reduction in blood pressure which was found to be significantly blocked by prior administration of atropine or promethazine. The chloroform fraction of the extract showed higher significant blood pressure lowering (hypotensive) activity than both the extract and n-butanol fraction. The leaves of B. axillaris have hypotensive action on blood pressure as claimed by ethnomedical practitioners. Journal of Pharmacy & Bioresources Vol. 2(2) 2005: 84-88