Oxidation of morin (2’,3,4’,5,7-Pentahydroxyflavone) with a peroxidase homogenate from onion

This study dealt with the examination of some biocatalytic properties of a peroxidase-active homogenate, obtained from onion solid wastes, using the flavonol morin (2’,3,4’,5,7-pentahydroxyflavone) as substrate. Morin oxidation by the homogenate/H2O2 system was shown to be optimum at pH values between 4 and 6 and temperature between 20 and 40°C. High performance liquid chromatography analyses of a peroxidase-treated morin solution revealed the formation of 2,4-dihydroxybenzoic acid (β-resorcylic acid), and 2,4,6-trihydroxybenzoic acid (phloroglucinol carboxylic acid) as two of the major degradation products. The tentative identification of these substances indicated that oxidative cleavage of morin by onion peroxidase shares common features with quercetin (3,4′,5′,5,7-pentahydroxyflavone) degradation, and putative routes were proposed.