Metabolic activation promotes estrogenic activity of the phytoestrogen-rich plant

Objective. There is evidence that metabolic activation can increase the estrogenic activity of the phytoestrogen-rich herb in tests with HepG2 cells. Variation in both plant genetics and harvest season may also influence estrogenic activity of the plant materials. We evaluated the influence of in vitro metabolic activation by S9 mixture on the estrogenic activity of tuberous samples of different cultivars of the phytoestrogen-rich herb, Pueraria mirifica, harvested in different seasons. Methods: Plant extracts were derived from the tubers of five plant cultivars collected during summer, rainy season and winter and administered to MCF-7 cultures, an ER alpha-positive human mammary adenocarcinoma cell line for 3 days at dosages of 0.1, 1, 10, 100 and 1000 mu g/ml. These data were compared with the major plant isoflavonoids puerarin, daidzin, genistin, daidzein and genistein and with 17 beta-estradiol, at concentrations of 10(-12) to 10(-6) M. The test system was done in the absence and presence of the S9 mixture. Results: The major plant isoflavonoids and the plant extracts exhibited variable degrees of estrogenic activities as evaluated by altered proliferation of the MCF-7 cell line which were significantly enhanced in the presence of the S9 mixture. Conclusion: Metabolic activation of plant isoflavonoids at least in vitro by S9 mixture plays a significant role in amplification of the estrogenic activity of the phytoestrogen-rich plant. In addition, the estrogenic activities of the plant samples were potentially influenced by both seasonal changes and plant genetics. (c) 2008 Elsevier Ireland Ltd. All rights reserved.