Abstract
Pharmacological studies on hirsutine (HS), hirsuteine (HST), rhynchophylline (RP), isorhynchophylline (IRP) and dihydrocorynantheine (DCT) which were isolated from the domestic phant Uncaria rhynchophylla MIQ. and β-yohimbine (β-Y) which was isolated from the domestic phant Amsonia elliptica ROEM. et SCHULT. were carried out. These alkaloids showed a mild central depressive effect in mice, a week non-competitive antispasmodic action in the mouse intestine, and a hypotensive effect in rats. Since β-Y showed α-adrenoceptor blocking action, the hypotensive effect of β-Y may be partly due to the vasodilative effect induced by its α-adrenoceptor blocking action. HS and β-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 β-adrenoceptor blocking action, the antiarrhythmic effects of HS would not be due to its β-adrenoceptor blocking effect.
