FIG. 1.

Structural formulas and carbon atom numbering of natural and synthetic isoflavonoids synthesized and used for biotransformation experiments. Isoflavonoids were classified into four groups, depending on the substitution pattern of ring A. Group 1 includes 7-hydroxy-8-methylisoflavone (1a), 7,4′-dihydroxy-8-methylisoflavone (1b), and 2′-fluoro-7-hydroxy-8-methylisoflavone (1c). Group 2 includes 7-hydroxyisoflavone (2a), 7,4′-dihydroxyisoflavone, or daidzein (2b). Group 3 includes 7,8-dihydroxyisoflavone (3a), 7,8,4′-trihydroxyisoflavone (3b), 7,8-dihydroxy-3′-methylisoflavone (3c), 4′-chloro-7,8-dihydroxyisoflavone (3d), and 7,8-dihydroxy-3′-trifluoromethylisoflavone (3e). Group 4 includes 6,7-dihydroxyisoflavone (4a), 6,7,4′-trihydroxyisoflavone (4b), 4′-chloro-6,7-dihydroxyisoflavone (4c), and 3′-chloro-6,7-dihydroxyisoflavone (4d).