Sinensetin, rutin, 3′-hydroxy-5, 6, 7, 4′-tetramethoxyflavone and rosmarinic acid contents and antioxidative effect of the skin of apple fruit

A GC–MS method was developed for the separation and quantifiation of three flavones: sinensetin (SEN), rutin (RU) and 3′-hydroxy-5, 6, 7, 4′-tetramethoxyflavone (TMF) and rosmarinic acid (RA), a caffeic acid derivative, in the skin of apple fruit collected from different local markets of Bangladesh. The results showed significant variation in the amount of these markers in methanolic extracts of skin samples from different markets of Bangladesh, even though the values were almost identical for most of the cases. A variation in antioxidant activities, ranging from 62.82 to 92.34%, and variations in total phenolics, ranging from 6.69 to 10.20 mg caffeic acid/g dry weight of the methanol extracts, were observed. Antioxidative potency of the methanolic extracts was comparable to that of pure quercetin and the synthetic antioxidant butylated hydroxylanisole (BHA).