To explore pharmacokinetic properties of prenylflavonoids from the Traditional Chinese Medicinal plant Epimedium, three doses of a standardized extract (100, 300 and 600 mg/kg
body weight), were administered to ovariectomized rats and serial blood samples were obtained. Serum concentrations of the Epimedium prenylflavonoids
icariin,
icariside I,
icariside II,
icaritin and
desmethylicaritin were determined by LC-MS/MS. Aliquots of sera were also applied to human cell lines that permanently express
ERalpha and
ERbeta proteins for the ex vivo measurement of estrogenic activity. All five prenylflavonoids exhibit non-linear dose-dependent increases in the area under concentration versus time curves. Two distinct pharmacokinetic patterns were evident, an early phase wherein
icariin and
icariside II reached t(max) 0.5-1 h, and a late phase wherein
icariside I,
icaritin and
desmethylicaritin peaked at t(max) 8h. Total concentrations of
icaritin and
desmethylicaritin reached C(max) approximately 2 microM and approximately 0.25 microM respectively. Estrogenic activity in Epimedium-treated rat sera lagged by several hours compared to animals treated with control drug
estradiol benzoate, corresponding to the appearance of bioactive metabolites
desmethylicaritin,
icaritin and
icariside I. Following
glucuronidase/sulphatase treatment, prolonged estrogenic activity at higher Epimedium doses (300 and 600 mg/kg of
body weight) was evident, and correlated with the persistence of micromolar levels of
icaritin at the 48-72 h sampling period. The depot effect resulted in time-concentration bioactivity profiles at the three Epimedium doses (area under curve 374, 543, and 771pME2 h(-1)) that exceeded that observed for
estradiol benzoate (148pME2 h(-1)). Our study correlated the pharmacokinetics of prenylflavonoids with the dynamics of their
estrogenic effects and reveals the potential estrogenicity of this Epimedium extract. This study may aid the development of prenylflavonoids as drugs for menopause and other conditions requiring estrogenic action.