New isoflavones, inhibiting catechol-O-methyltransferase, produced by Streptomyces.

In the screening of catechol-O-methyltransferase inhibitors in streptomyces culture filtrates, three new isoflavones were isolated. Their structures were shown to be 3',5,7-trihydroxy-4',6-dimethoxyisoflavone (I), 3',5,7-trihydroxy-4',8-dimethoxyisoflavone (II), 3',8-dihydroxy-4',6,7-trimethoxyisoflavone (III). I and II inhibited both catechol-O-methyltransferase and dopa decarboxylase, and showed hypotensive action. III was a specific inhibitor of catechol-O-methyltransferase, and showed no hypotensive action.