PRODUCTS OF PEROXIDASE-CATALYZED OXIDATION OF 4,2',4'-TRIHYDROXYCHALCONE

The enzyme responsible for the previously reported oxidation of 4,2'',4''-trihydroxychalcone to the corresponding dihydroflavonol and hydrated aurone in cell-free extracts of garbanzo seedlings (Cicer arietinum) was identified as peroxidase (EC 1.11.1.7). Studies with the partially purified enzyme and with commercial horse radish peroxidase showed that the initial product of the enzymic reaction under these conditions was an unstable compound, characterized as the novel 4-membered cyclic peroxide (1,2-dioxetane) derivative of the chalcone. Various stereochemical modifications of the cyclic peroxide were isolated, and these readily convert chemically to a 2nd novel compound, a benzoxepinone-spiro-cyclohexadienone isomeric with 7,4''-dihydroxyflavonol. This flavonol was also obtained as a chemical transformation product of the cyclic peroxide enzymic products.