COMPARATIVE DEGRADATION PATHWAYS OF MALVIDIN 3,5-DIGLUCOSIDE AFTER ENZYMATIC AND THERMAL TREATMENTS

Some kinetic properties of an industrial anthocyanin-beta-glucosidase (anthocyanase), Pectinol DL, with malvidin 3-monoglucoside and malvidi n 3,5-diglucoside (malvin) as substrates, have been studied at pH 3 an d 6. Pectinol DL is more active at pH 3 than at pH 6, the enzyme affin ity being greater with malvidin 3-monoglucoside as a substrate (K-m = 0.72 mM) than with malvin (K-m = 3.2 mM). After hydrolysis of O-glucos idic bonds of malvin by pectinol DL, the aglycone was very quickly des troyed. By TLC, GC and MS analysis, syringic acid and 2,4,6-trihydroxy benzaldehyde were identified. The same breakdown products were found a fter heating an aqueous solution of malvin at pH 3. An additional prod uct was identified as phloroglucinol. From these results, it can be po stulated that the aglycone is degraded according to a chemical mechani sm proceeding to a carbon-carbon bond breakdown from the chalcone form .