Isolation of isoflavones inhibiting dopa decarboxylase from fungi and streptomyces.

Abstract

By screening of culture filtrates of fungi [Stemphylium sp., Aspergillus niger, Orobus tuberosus] and Streptomyces [neyagawaensis var. orobolere] for activity to inhibit dopa decarboxylase, the following isoflavone compounds were obtained: psi-tectorigenin (I), genistein (II), orobol (IV), 8-hydroxygenistein (V) and a new compound (III). III was elucidated to be 3'',4'',5,7-tetrahydroxy-8-methoxy isoflavone. Among these isoflavones, IV and III showed the strongest activity in inhibiting dopa decarboxylase. All these isoflavones also inhibited histidine decarboxylase and catechol-O-methyl-transferase. Activities of these compounds to inhibit tyrosine hydroxylase and dopamine .beta.-hydroxylase were examined. Orobol which showed no or only slight inhibition of tyrosine hydroxylase and dopamine .beta.-hydroxylase exhibited a significant hypotensive effect on spontaneously hypertensive rats.