Intermolecular copigmentation between anthocyanidin-3,5-O-diglucosides and three phenolic compounds: Insights from experimental and theoretical studies

Anthocyanidin-3,5- O -diglucosides are the main pigments in red wines made from non- vinifera and hybrid species. In this work, intermolecular copigmentation between three common anthocyanidin-3,5- O -diglucosides and three types of phenolic copigments was systematically investigated in model wine solutions through experimental and theoretical methods. The impact of the sugar moiety at the C5 position of anthocyanin A ring was studied emphatically. Results showed that the anthocyanidin-3,5- O -diglucosides produced much stronger hyperchromic effects compared to the anthocyanidin-3- O -glucosides. Thermodynamic analysis and theoretical calculations suggested higher affinity of the anthocyanidin-3,5- O -diglucosides towards copigments (larger K values and lower ∆ G ) than corresponding monoglucosidic anthocyanins, mainly due to the enhancement of hydrogen bonds and van der Waals forces resulting from the additional glucose. In conclusion, the results revealed that the glucose at the C5 position of anthocyanin A ring could play a positive role in copigmentation, thus may lead to strong copigmentation effects in these wines.