OBJECTIVETo investigate the estrogen-like activities of icariin (ICA), icaritin (ICT) and desmethylicaritin (DICT) and their structure/activity relationships.

METHODSICT was hydrolyzed from ICA by cellulase and then DICT was demethylated from ICT in boron tribromide and dichloromethane system. Estrogen-sensitive MCF-7 cells and T47D cells were co-incubated with different concentrations of test compounds for 6 and 9 d respectively, and the cell proliferation was measured by MTT.

RESULTSICT and DICT both markedly enhanced cell proliferation. Compared with estradiol (10.(-9) mol/L), the proliferative effects of 10.-6 mol/L ICT and DICT on MCF-7 cells were 90.0% and 94.0% (P<0.01), respectively, and those of T47D cells were 65.6% and 50.0%. (P<0.01). But this phenomenon was not observed with ICA. Cell proliferation induced by ICT and DICT was completely antagonized by 10.(-7 )mol/L pure estrogen receptor antagonist, ICI182,780.

CONCLUSIONICT and DICT possess estrogen-like activity of enhancing proliferation in MCF-7 and T47D cells. However, ICA appears to have no estrogenicity on MCF-7 and T47D cell lines in vitro.