The phytoestrogenic potential of flavonoid glycosides from Selaginella moellendorffii via ERα-dependent signaling pathway

Selaginella moellendorffii (SM) has been applied as an ethnic drug to treat conditions such as osteoporosis, idiopathic thrombocytopenic purpura, and chronic inflammation. It is known to be rich in flavonoids, including apigenin glycosides and unique elements of bioflavonoids. To investigate estrogen-like constituents of SM and the possible mechanism. We identified the main components in liquid chromatography and liquid chromatography-mass spectrometry. The estrogenic effects were examined using a recombinant yeast screening assay, an E-screen cell proliferation assay, and an in vivo uterotrophic assay. Flavonoid glycosides extract, some flavonoid glycosides, and apigenin showed estrogen agonistic activity in the yeast screening assay. They also induced cell proliferation in estrogen receptor-positive (ER+) cells but not in estrogen receptor-negative (ER-) cells. Consistently, the protein expression of ERα, phosphorylation protein kinase B (p-AKT), phosphatidylinositol 3 kinase (PI3K), phosphorylation mammalian target of rapamycin (p-mTOR), phosphorylation 38,000-Da protein (p-P38), and phosphorylation extracellular-regulated kinase 1/2 (p-ERK1/2) elevated following treatment with flavonoid glycoside extract (P < 0.01 or P < 0.05). These effects could be blocked by ER antagonist or ERα antagonist but not be blocked by ERβ antagonist. In vivo assay, flavonoid glycoside extract could significantly increase body weight, serum estradiol level, uterine wet weight, alter uterine morphology, and promote ERα protein expression (P < 0.01 or P < 0.05). ERα induction via mitogen-activated protein kinases (MAPK) and PI3K/Akt/mTOR pathways might be the possible mechanism underlying the phytoestrogen effect of SM, and the flavonoid glycosides might be the critical estrogenic constituents.