Two new compounds and anti-complementary constituents from Amomum tsao-ko

Two new compounds, (2R,3R,4R)-3',5'-dimethoxy-3,4,7,4'-tetrahydroxy-flavan (1) and 2-(4-hydroxy-3-methoxybenzoyl)-4-methoxy-benzaldehyde (2), together with 35 known phenolic compounds were obtained from the fruits of Amomum tsao-ko. Structures of the new compounds were elucidated on the basis of spectroscopic means, including 2D NMR, a n d high-resolution M S analysis. The isolated compounds were tested in vitro for t heircomplement-inhibitory properties against the classical pathway (CP) and alternative pathway (AP). The results showed that 14 compounds exhibited anti-complementary activities against the CP and AP with CH50 values of 0.42 - 4.43 mM and AP50 values of 0.53 -1.51 mM. Preliminary mechanism studies showed that 1,7-bis(4-hydroxyphenyl)-4(E)-hepten-3-one (8) blocked C1q, C2, C3, C4, C5 and C9 components of the complement system, and hydroquinone (15) acted on C1q, C2, C3, C5 and C9 components.