SYNTHESIS OF BETA-IONONE IN AN ALDEHYDE XANTHINE OXIDASE/BETA-CAROTENE SYSTEM INVOLVING FREE-RADICAL FORMATION/

The enzymic cooxidation of beta-carotene (BC) by xanthine oxidase (XO) in aqueous : solutions leads to beta-ionone (BI) and derivatives: epo xy-beta-ionone (EPBI), dihydroactinidiolide, beta-cyclocitral, pseudoi onone, etc. We demonstrate, in this article, that this is due to free radical (R.) formation during the first hour of stirring and the use o f aldehydes as substrate. The bleaching of BC does not occur when the common substrate of XO, xanthine, is used; this proves that the supero xide anion O-2.- alone is not active on BC. BI formation in this case is not observed.