Two compounds were isolated from biotransformation of daidzein, a soybean isoflavone, by Aspergillus oryzae. One was 6,7,8,4′-tetrahydroxyisoflavone, an A-ring dihydroxylated daidzein, and the other was a novel compound which had the cleaved B-ring of daidzein. The former was perhaps derived from 8-hydroxydaidzein and/or 6-hydroxydaidzein, and had high DPPH radical-scavenging activity.
