Anti-complement activity of isolated compounds from the roots of Clerodendrum bungei Steud

To determine the anti-complement activity of natural diterpenes, chromatographic separation of the acetone-soluble fraction from the roots of Clerodendrum bungei (Verbenaceae) led to the isolation of five diterpenoids. An acetone-soluble extract of the roots of C. bungei exhibited significant anti-complement activity on the classical pathway complement system, which was expressed as total hemolytic activity. Five compounds isolated from the roots of C. bungei, namely 12-O-β-d-glucopyranosyl-3,11,16-trihydroxyabieta-8,11,13-triene (1), 3,12-O-β-d-diglucopyranosyl-11,16-dihydroxyabieta-8,11,13-triene (2), ajugaside A (3), uncinatone (4) and 19-hydroxyteuvincenone F (5). Compounds 1, 2, 3, 4 and 5 showed inhibitory activity against complement system with 50% inhibitory concentrations (IC(50)) values of 24 µm, 138 µm, 116 µm, 87 µm and 232 µm. Among the compounds tested, 1 showed the most potent anti-complement activity (IC(50), 24 µm).