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 malvidin 3,5-diglucoside (malvin) as substrates, have been studied at pH 3 and 6. Pectinol DL is more active at pH 3 than at pH 6, the enzyme affinity 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-glucosidic bonds of malvin by pectinol DL, the aglycone was very quickly destroyed. By TLC, GC and MS analysis, syringic acid and 2,4,6-trihydroxybenzaldehyde were identified. The same breakdown products were found after heating an aqueous solution of malvin at pH 3. An additional product was identified as phloroglucinol. From these results, it can be postulated that the aglycone is degraded according to a chemical mechanism proceeding to a carbon-carbon bond breakdown from the chalcone form.