Color and antioxidant properties of cyanidin-based anthocyanin pigments.

A series of cyanidin-based anthocyanin pigments was investigated to determine the effect of structural variation on a number of chemical and physical properties: CIELAB color coordinates, visual detection thresholds, hydration constants (pK(H)), and in vitro antioxidant activities (ORAC). In addition to individual isolated compounds, purified total pigment isolates from blackberry, elderberry, black carrot, red cabbage, and sweet potato were also examined. Acylation with cinnamic acids shifted color tonality (hue angle) to purple, and markedly increased pK(H) and antioxidant activity, but lowered the visual detection threshold. Glycosidic substitution at the 5 position moved tonalities toward purple and decreased pK(H), and tended to lower the ORAC value, but raised the visual detection threshold. Increasing the number of sugar substituents at the 3 position also affected all of these parameters, however, the extent was not predictable. Antioxidant levels of purified anthocyanin extracts were much higher than expected from anthocyanin content indicating synergistic effect of anthocyanin mixtures.