A marine Streptomyces sp. 060524 capable of hydrolyzing the glycosidic bond of isoflavone glycosides, was isolated by detecting its b-glucosidase activity. 5 isoflavone aglycones were isolated from culture filtrates in soybean meal glucose medium. They were identified as genistein (1), glycitein (2), daidzein (3), 3 0 ,4 0 ,5,7-tetrahydroxyisoflavone (4), and 3 0 ,4 0 ,7-trihydroxyisoflavone (5), based on UV, NMR and mass spectral analysis. The Streptomyces can selectively hydroxylate at the 3 0 -position in the daidzein and genistein to generate 3 0 -hydroxydaidzein and 3 0 -hydroxygenistein, respectively. The Strain biotransformed more than 90% of soybean isoflavone glycosides into their aglycones within 108 h. 3 0 -hydroxydaidzein and 3 0 -hydroxygenistein exhibited stronger cytotoxicity against K562 human chronic leukemia than daidzein and genistein.
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