Tracheal relaxant activity of cissaglaberrimine and trilobinine, two aporphinic alkaloids from Cissampelos glaberrima

In the present work we studied the relaxant effect of two aporphinic alkalo ids isolated from the roots barks of Cissampelos globerrima St. Hil. (Menis permaceae), (+)-cissaglaberrimine (CGE; a tertiary alkaloid) and (+)-trilob inine (TBE; a quaternary alkaloid). In guinea-pig tracheal preparations, CG E and TBE reduced the spontaneous tone and inhibited the contractions induc ed by carbachol and histamine. TBE was 6 times more potent than CGE in redu cing the spontaneous tone and it was also 1.5 times more potent in antagoni sing the effects of carbachol and histamine. The inhibitory effect of CGE i n contractions induced by histamine was not attenuated in the presence of t imolol (10 mu M). However, in the same experimental conditions, timolol alm ost completely abolished the inhibitory effect of TBE. These results showed that the relaxations induced by TBE were dependent on the activation of be ta(2)-adrenoceptors, while the mechanism involved in relaxations induced by CGE remains to be determined.