Blockade of the bradykinin-evoked diphasic response of isolated rat duodenum by the crude extract of and compounds obtained from Mandevilla velutina.

The influence of an aqueous/ethanolic extract of M. velutina (CE) and of two compounds (MV 8608 and MV 8612) purified from the plant on BK-, Ad- and K+-induced responses of the rat duodenum was analyzed in vitro. In preparations precontracted with Ca2+, the CE (1 and 2 mg/ml) markedly inhibited BK-induced relaxation in a dose-dependent manner but was less effective against Ad-induced relaxation. The CE (0.5 mg/ml) also antagonized BK-induced relaxation and contraction of strips bathed in normal medium. The two compounds from M. velutina (10 and 20 micrograms/ml) also promoted a dose-dependent blockade of both responses to BK, only slightly depressing the response to K+.