Keracyanin (chloride) is a polyphenolic anthocyanin found naturally in many plants. It has high antioxidant activity, protecting erythrocytes from apoptosis. However, keracyanin (chloride) impairs growth and induces apoptosis in the highly tumorigenic RE-149 DHD cell line. It inhibits a range of mammalian and bacterial proteases, including neutrophil elastase, matrix metalloproteinase-1 (MMP-1), and MMP-9 at concentrations of 6.25-50 μg/ml. When added to food, keracyanin (chloride) significantly reduces body weight gain, resistance to insulin, and lipid accumulation in mice fed a high-fat diet.