REACTIONS OF POLYPHENOLOXIDASE GENERATED CAFTARIC ACID O-QUINONE WITHMALVIDIN 3-O-GLUCOSIDE

Polyphenol oxidase (PPO)-catalysed oxidation of solutions containing m alvidin 3-O-glucoside and caftaric acid was studied by HPLC and mass s pectrometry. The reaction of the anthocyanin with o-quinones and the n ature of the products formed were compared as two pH values. The oxidi zed solution contained, in addition to the precursors, coloured and co lourless compounds which eluted between caftaric acid and malvidin 3-O -glucoside. Liquid chromotography. with ion spray mass spectrometry (L C-ISP-MS) indicated that they were adducts of malvidin 3-O-glucoside a nd caftaric acid, either in the flavylium or in the hemiacetal form. ( C) 1997 Elsevier Science Ltd. All rights reserved.