Behavior of 3-deoxyanthocyanidins in the presence of phenolic copigments

Anthocyanin stability and color intensity are generally improved in the presence of copigments in moderately acidic environments. The 3-deoxyanthocyanins on the other hand are fairly stable to color loss due to change in pH. It is unknown, therefore, how they behave in the presence of copigments. We studied the effects of common phenolic copigments, tannic, ferulic, and O-coumaric acids, and rutin on behavior and stability of six 3-deoxyanthocyandins over 4.5 months. Tannic and ferulic acid produced the most significant bathochromic shift, whereas rutin had no bathochromic effect. None of the copigments produced a significant hyperchromic shift with the pigments, implying colored species of the pigments were predominant under conditions used. Ferulic and tannic acids were the most effective at improving color stability of 5-hydroxylated pigments, whereas tannic acid and rutin improved the stability of 5-methoxylated pigments the most. Substitution at C-5 was key to overall behavior of the 3-deoxyanthocyanidins.