Potent antioxidative isoflavones isolated from soybeans fermented with Aspergillus saitoi
1998
Esaki, H. (Sugiyama Jogakuen Univ., Nagoya (Japan)) | Onozaki, H. | Morimitsu, Y. | Kawakishi, S. | Osawa, T.
Two potent antioxidative isoflavones were isolated from soybeans fermented with Aspergillus saitoi by silica gel column chromatography and preparative HPLC, using ODS column, or in addition, Toyopearl HW-40 column chromatography. The purified AS-13 and AS-9B compounds were identified as 8-hydroxydaidzein (8-OHD) and 8-hydroxygenistein (8-OHG), respectively, by Ms, and 1H-NMR, 13C-NMR and HMBC spectra. These isoflavones, which have an o-dihydroxy structure between the 7- and 8-position, each exhibited significantly stronger antioxidative activity than daidzein and genistein in both oil and lipid/aqueous systems. Furthermore, the antioxidative activity and the content of each isoflavone analog in soybeans with different fermentation periods were investigated. It is suggested from these results that AS-13 and AS-9B were produced from daidzein and genistein, respectively, by hydroxylation at the 8-position of each isoflavone structure. In addition, it is concluded that these isoflavones were also the principal antioxidants in potent antioxidative soybeans fermented with A. saitoi
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