DETECTION OF COMPOUNDS FORMED THROUGH THE REACTION OF MALVIDIN 3-MONOGLUCOSIDE AND CATECHIN IN THE PRESENCE OF ACETALDEHYDE

The interaction between catechin and malvidin 3-monoglucoside in the presence of acetaldehyde was studied in model solutions. The initial formation of two pigments (I and II), which later evolved to more condensed structures, was observed. Evidence was found that for these pigments to be formed, catechin should first react with acetaldehyde and the resulting adduct later condenses with anthocyanin; it is proposed that pigments I and II are two enantiomeric structures of the catechin(8-->)-acetyl-(-->8)-anthocyanin dimer. For their formation, a relatively acidic pH is necessary; this is attributed to the demand that the acetaldehyde should be in cationic form for condensation to occur. Condensation among catechin units involving acetaldehyde was also seen. Minor amounts of substances from the degradation of anthocyanin were detected, indicating that in the presence of acetaldehyde it is basically condensation and not degradation of the anthocyanin that occurs.