Conversion of Flavanone to Flavone, Dihydroflavonol and Flavonol with an Enzyme System from Cell Cultures of Parsley

Soluble enzyme preparations from irradiated cell suspension cultures of parsley (Petroselinum hortense Hoffm.) catalyse the conversion of flavanone to flavone, dihydroflavonol and flavonol. These reactions require 2-oxoglutarate, Fe2+ and ascorbate as cofactors. In the presence of these cofactors conversion of dihydroflavonol to flavonol was also observed. With this system in vitro biosynthesis of radioactive flavone, dihydroflavonol and flavonol from [2-14C]malonyl-CoA and 4-coumaroyl-CoA in good yield and with high specific activity is possible. We postulate that synthesis of flavone and flavonol from flavanone proceeds via 2-hydroxy-and 2,3-dihydroxyflavanone, respectively, with subsequent dehydration. The microsomal fraction of the parsley cells contains an NADPH-dependent flavanone 3'-hydroxylase.