Anti-complement activity guided fractionation led to the isolation of 24 compounds from Commelina communis.Bioassay showed that six compounds inhibited the classical pathway and alternative pathway with CH 50 values of 0.12-1.44 mM and AP 50 values of 0.28-7.05 mM,respectively.Preliminary mechanism studies demonstrated that quinovic acid acted on C1q,C2,C3,C4,C5 and C9 components of the complement system,β-sitosterol interacted with C3 and C4,（＋）-catechin-3-O-β-Dgluco（2-cinnamoyl）-pyranoside,p-cresol and 6-methoxy-3-methylbenzene-1,2,4-triol blocked C1q,C2,C3,C5 and C9.
