A Chinese herbal preparation, QingE formula (QEF), has long been used clinically in China for treating osteoporosis, particularly in postmenopausal woman, by virtue of its kidney-invigorating function, but there have been no studies to investigate its mechanism, in particular to link it to estrogen replacement therapy.In the present work we undertake a characterization of estrogenic activity of QEF for treating postmenopausal symptoms using an in vivo model of ovariectomized (OVX) mice together with in vitro studies with the MCF-7 breast cell for further molecular characterization of QEF activity.Immature mice were used to screen active herbs and the MCF-7 cell proliferation was used to screen the active components from active herbs.OVX mice were treated intragastrically with QEF at doses of 0.85, 1.7 and 3.4 g· kg-1· d-1 for four weeks.As a positive control one group of mice were treated with an estrogen agonist nilestriol (0.5 mg· kg-1).Compared with untreated OVX controls, both QEF and nilestriol treatments restored the estrous cycle and demonstrated significant and clear estrogenic activity as indicated by reversal of uterine atrophy (up to a six-fold increase in uterine weight induced by QEF or nilestriol), reduction in rectal temperature and increased expression (1.6-fold) of estrogen receptors in uterine tissue.Notably the largest changes in these three parameters were found in OVX mice treated with the lowest dose of QEF.At the highest dose of QEF, 3.4 g· kg-1, significant changes were found in adrenal gland weight (30% increase), serum E2 (60% increase) and serum LH (17% decrease) compared with untreated 0VX controls, whereas the lower doses of QEF induced no significant changes.The data suggest that estrogenic responses induced by QEF show tissue variation that may reflect different affinities of estrogen receptors for QEF components.An extract of QEF could significantly induce luciferase expression (2.7-fold compared with control) from an estrogen response element (ERE) luciferase reporter expressed in MCF-7 cells and Similarly the extract could induce expression of both ER and ER (1.2-fold and 1.7-fold respectively) forms of the estrogen receptor.In both assays the activity of the QEF extract was inhibited 80-90% by the ER antagonist ICI 182,780 and indicate that QEF extract contains estrogenic components.Animal and cells experimental results showed the primary herbs eucommiae and psoralea were acting as estrogens in the formula, estrogenic activity of flavonoids, lignans, and coumarins 23 compounds from eucommiae and psoralea were screened.In summary the study demonstrates that the activity of QingE formula is mediated through estrogenic components, currently undergoing characterization, and provides an evidence-base for the use of QingE to treat post-menopausal symptoms in women.