[Pharmacological studies of indole alkaloids obtained from domestic plants, Uncaria rhynchophylla Miq. and Amsonia elliptica Roem. et Schult].

Pharmacological studies on hirsutine (HS), hirsuteine (HST), rhynchophylline (RP), isorhynchophylline (IRP) and dihydrocorynantheine (DCT) which were isolated from the domestic plant Uncaria rhynchophylla Miq. and beta-yohimbine (beta-Y) which was isolated from the domestic plant Amsonia elliptica Roem. et Schult. were carried out. These alkaloids showed a mild central depressive effect in mice, a week non-competitive anti-spasmodic action in the mouse intestine, and a hypotensive effect in rats. Since beta-Y showed alpha-adrenoceptor blocking action, the hypotensive effect of beta-Y may be partly due to the vasodilative effect induced by its alpha-adrenoceptor blocking action. HS and beta-Y showed a preventive effect on the development of gastric erosions in mice. HS had antiarrhythmic effects on both aconitine-induced arrhythmias in mice and ouabain-induced arrhythmias in guinea pigs. The potency of the antiarrhythmic effects induced by HS was approximately the same as that of ajmaline, an indole alkaloid. Since HS did not show beta-adrenoceptor blocking action, the antiarrhythmic effects of HS would not be due to its beta-adrenoceptor blocking effect.