Abstract
By screening of culture filtrates of fungi and streptomyces 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-methyltransferase. Activities of these compounds to inhibit tyrosine hydroxylase and dopamine β-hydroxylase were examined. Orobol which showed no or only slight inhibition of tyrosine hydroxylase and dopamine β-hydroxylase exhibited a significant hypotensive effect on spontaneously hypertensive rats.
