No abstract

During our studies on the metabolism of kobophenol A (1) in rats, we had isolated, purified, and identified the main new oxidative metabolite of 1, koboquinone A (2) from rats' feces. To elucidate the metabolic pathway of 1 in rats, we conducted the in vitro metabolic experiments of 1 by human intestinal bacteria and found that Klebsiella pneumoniae produced appreciable amounts of 2. This was verified by means of high performance liquid chromatography mass/mass spectrometry (HPLC/MS/MS) analysis.

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The conversion from kobophenol A into carasinol B, two main chemical constituents of Caragana sinica, was confirmed by in vitro acid-catalyzed epimerization. The result provides important information about the biotransformation of kobophenol A in plants and its metabolism in rats.

The biological effects of soy isoflavones have attracted considerable interest in recent years, leading to numerous studies on dietary intake and epidemiology. (-)-(S)-equol (3) is a metabolite produced in vivo from the isoflavone daidzein, a kind of soy phytoestrogen, by the action of gut microflora. It has higher biological activity than its precursor. Here, we wish to report the isolation and first X-ray crystal structure of 3 from the feces of rats fed a soy-isoflavone-containing diet.