Supramolecular Study of the Interactions between Malvidin-3--Glucoside and Wine Phenolic Compounds: Influence on Color.

Supramolecular study of the interactions between the major wine anthocyanin, malvidin-3--glucoside (Mv3G) and different wine phenolic compounds (quercetin 3--β-glucopyranoside (QG), caffeic acid, (-)-epicatechin, (+)-catechin, and gallic acid) has been performed at two different molar ratios (1:1 and 1:2) in acidic medium where flavylium cation predominates (pH ≤ 2). Color variations have been evaluated by differential colorimetry using CIELAB color space. These studies have been complemented with isothermal titration calorimetry assays and molecular dynamics simulations. The color of Mv3G flavylium cation is modified by the interaction with QG toward more bluish and intense colors. Interaction constants between the anthocyanin and the different phenolic compounds were obtained, ranging from 9.72 × 10 M for QG to 1.50 × 10 M for catechin. Hydrophobic interactions and H-bonds are the main driving forces in the pigment/copigment aggregation, except for the interactions where caffeic acid is involved, in which hydrophobic interactions acquire greater preponderance.