Anti-complementary activity of protostane-type triterpenes fromAlismatis rhizoma

Abstract

Four protostane-type triterpenes, alisol B 23-acetate (1a), alisol C 23-acetate (2a), alisol B (3a), and alisol A 24-acetate (4a), were isolated from the rhizome ofAlismatis plantago-aquatica L. var.orientate Samuelson (Alismataceae) and eleven protostane derivatives (compounds1-11) were obtained by selective modification from alisol B 23-acetate (1a). These compounds were investigated for their anti-complement activity against the classical pathway of the complement system. Alisol B (3a) and alisol A 24-acetate (4a) exhibited anti-complement activity with IC₅₀ values of 150 and 130 μM. Among the synthetic derivatives, the tetrahydroxylated protostane triterpene (9) showed moderate inhibitory activity with IC₅₀ value of 97.1 μM. Introduction of an aldehyde group at C-23 (10; IC₅₀ value, 47.7 μM) showed the most potent inhibitory effect on the complement systemin vitro