Antioxidant Activities of Selected Berries and Their Free, Esterified, and Insoluble-Bound Phenolic Acid Contents

To explore the potential of berries as natural sources of bioactive compounds, the quantities of free, esterified, and insoluble-bound phenolic acids in a number of berries were determined. In addition, the antioxidant activities of the berries were determined using 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity, ferric reducing antioxidant power, and Trolox equivalent antioxidant capacity assays, in addition to determination of their metal ion chelating activities. Furthermore, several phenolic compounds were detected using high-performance liquid chromatography. Of the 6 tested berries, black chokeberry and blackberry exhibited the strongest antioxidant activities, and the various berry samples were found to contain catechin, caffeic acid, p-coumaric acid, epicatechin, vanillic acid, quercitrin, resveratrol, morin, naringenin, and apigenin. Moreover, the antioxidant activities and total phenolic contents of the fractions containing insoluble-bound phenolic acids were higher than those containing the free and esterified phenolic acids. The results imply that the insoluble-bound fractions of these berries are important natural sources of antioxidants for the preparation of functional food ingredients and preventing diseases associated with oxidative stress.