Anthocyanin
Anthocyanins are a class of pigments found in ecocyanina (grape extract) and other plants. The anthocyanins from grapes have antifungal activity, an inhibitory effect on the growth of the bacteria lactobacillus acidophilus, and bioflavonoid activity. Anthocyanins have been used as coloring agents in beverages. Depending upon the acidity of the solution, the color may vary from red to purple.
References
Leung, Albert Y. 1980. Encyclopedia of Common Natural Ingredient used in Food, Drugs and Cosmetics. John Wiley and Sons, N Y. 409 pp.