In vitro and cellular antioxidant activities of 3-deoxyanthocyanidin colourants

3-Deoxyanthocyanidins are a rare type of plant colourant with potential high antioxidant activity. This study investigated the in vitro and cellular antioxidant activity of four 3-deoxyanthocyanidins: apigeninidin, 7-methoxy-apigeninidin, luteolinidin and 5,7-dimethoxy-luteolinidin, compared to a common anthocyanidin: cyanidin, and several well-known antioxidants. The aim was to understand the antioxidant potency of 3-deoxyanthocyanidins and their structure-activity relationships. The 3-deoxyanthocyanidin luteolinidin and 5,7-dimethoxy-luteolinidin and the anthocyanidin cyanidin consistently demonstrated significantly high antioxidant activity in all assays. The results showed that the antioxidant activity of 3-deoxyanthocyanidins was highly structurally dependent. The A-ring OCH 3 , B-ring catechol and C-ring C3–OH groups all had significant influences on the antioxidant activity, and the B-ring catechol group was essential for high antioxidant activity of 3-deoxyanthocyanidins in all the assays. This was the first study evaluating the cellular antioxidant activity of 3-deoxyanthocyanidins, and the results suggested that luteolinidin and 5,7-dimethoxy-luteolinidin might be good candidates for development as antioxidant supplements.