Über die Bedeutung der Isoflavanone bei der Isoflavonbiosynthese

Abstract

The occurrence of isoflavanones in Cicer arietinum was investigated. The presence of homoferreirin (5,7-dihydroxy-2′,4′-dimethoxyisoflavanone) was demonstrated but no isoflavanones with the same substitution pattern as the isoflavones occuring in this plant could be found. Soja seedlings (Soja hispida) are able to dehydrogenate dihydrodaidzein (7,4′-dihydroxyisoflavanone) to daidzein, as was shown with tritium labeled dihydrodaidzein. 7,4′-Dihydroxyflavanone- [2-14C] which was fed to the seedlings simultaneously with the dihydrodaidzein was incorporated into daidzein to about the same extent as dihydrodaidzein. Part of the daidzein is excreted into the medium by the seedlings. 7,4′-Dihydroxyflavanone- [2-14C-3-T2] was synthesized. When this compound was incorporated into 7-hydroxy-4′-methoxyisoflavone (formononetin) in chana seedlings (Cicer arietinum L.) the T/14C ratio dropped by 99 per cent. In contrast, when 5,7,4′-trihydroxyflavanone- [2-14C-2-T] was incorporated into 5,7-dihydroxy-4′-methoxyisoflavone (biochanin A) the T/14C ratio stayed constant. The results are discussed in the light of possible mechanisms for the 2,3-aryl migration occurring during isoflavone biosynthesis and in relation to the biogenetic relation-ships of isoflavones and isoflavanones.