Malvidin-3-glucoside chloride (Oenin chloride) has antioxidant activity, alone is not oxidized in the presence of grape polyphenol oxidase. Malvidin-3-O-glucoside chloride's color stabilization at a higher pH can be explained by self-aggregation of the flavylium cation and copigmentation with the Z-chalcone form.

Here we used a gel electrophoresis assay employing supercoiled DNA plasmid to examine the ability of these compounds (1) to intercalate DNA, (2) to inhibit human topoisomerase I through both inhibition of plasmid relaxation activity (catalytic inhibition) and stabilization of the cleavable DNA-topoisomerase complex (poisoning), and (3) to inhibit or enhance oxidative single-strand DNA nicking. We found no evidence of DNA intercalation by anthocyan(id)ins in the physiological pH range for any of the compounds used in this study-cyanidin chloride, cyanidin 3-O-glucoside, cyanidin 3,5-O-diglucoside, Malvidin-3-O-glucoside chloride and luteolinidin chloride. The anthocyanins inhibited topoisomerase relaxation activity only at high concentrations (> 50 muM) and we could find no evidence of topoisomerase I cleavable complex stabilization by these compounds.