prim-O-Glucosylcimifugin (PGCN), a highest content chromone in the roots of Saposhnikovia divaricata, was incubated with human intestinal flora (HIF), and two biotransformation products were obtained from the incubated solution by chromatographic methods. The chemical structures of the two biotransformation products were elucidated as cimifugin (CN) and 5-O-methylvisamminol (MVL), respectively, on the basis of NMR and MS data. The biotransformation product CN was formed through a deglucosylation of PGCN by β-glucosidase secreted from the HIF, and then the hydroxymethyl group of CN was reduced to lead to occurrence of MVL. All of these compounds were evaluated for their effect on the inhibition of nitric oxide production induced by lipopolysaccharide in macrophage cell line RAW 264.7 and for 1,1-diphenyl-2-picrylhydrazyl free-radical scavenging activity in cell-free bioassay system.