Enhanced Estrogenic Activity of Soybean Isoflavones by Coadministration of Liuwei Dihuang Pills in Ovariectomized Rats.

Soybean isoflavones are beneficial for treating hormone-related diseases. Simultaneous consumption of soybean isoflavones and Liuwei Dihuang pills (LWPs) is effective for treating perimenopausal period syndrome. However, why the combination of isoflavones and LWPs is more effective than ingestion of each component alone remains unknown. Here, we show that enhanced estrogenic activities would appear when the ovariectomized rats were fed with a soybean diet in combination of LWPs treatment. Our further studies explored enhancements of Lactobacillus (19-fold) and Bifidobacterium (12-fold) contents in the intestine of rat and 1.84-fold higher intestinal β-glucosidase activity in LWPs treatment group compared with the control group. As a result, steady-state concentrations of genistein (1.20-fold), daidzein (1.36-fold), and equol (1.43-fold) in serum were significantly elevated in the combination group compared with the soybean alone group. The results present the first evidence of the mechanism of enhanced estrogenic activity of dietary soybean isoflavones in combination with LWPs. Our study indicates that alterations of gut bacteria after LWPs treatment play a key role in the enhanced estrogenic effect of dietary soybean, suggesting a direct relationship between dietary soybean, LWPs, and gut flora.