Evaluation of the antioxidant activity of phenolic compounds among blueberry cultivars by HPLC-ESI/MS and on-line HPLC-ABTS system

Abstract

Antioxidant compounds are now of considerable interest due to their effect of preventing or delaying aging and their apparent involvement in prevention of common cancers. In the present study, the fruits and leaves from a number of high bush blueberry cultivars (Vaccinium corymbosum L.) were investigated for their antioxidant capacity. The antioxidant constituents in the blueberry fruit were identified by LC-ESI/MS and their individual antioxidant capacities were evaluated by on-line HPLC-ABTS (2,2'-azinobis-3-ethylbenzothiazoline-6-sulphonic acid) system. The result showed that the amount of chlorogenic acid in the leaves was 6- to 11-times higher than that in the fruits and its antioxidant activity (AA) ranged from ca. 81.9 to 91.9% of total AA in the leaves and ca. 35.4 to 61.7% in the fruits. The sum of AA among the five major anthocyanins in the fruits was ca.23.5 to 38.6% of total AA among blueberry cultivars. The highest AA associated with fruit anthocyanins was due to delphinidin-3-galactose, which showed a weak negative correlation with AA of chlorogenic acid. The amount of total phenolic compounds exhibited similar patterns to the values of total AA in all cultivars, suggesting AA arises primarily from phenolic compounds in blueberry cultivars. These results demonstrated that the relative composition of phenolic compounds and their individual antioxidant activities were successfully assessed without purification of each constituent by applying an on-line HPLC-ABTS method. This method can be applied to a broad range of functional food products that have high antioxidant potential. Key words: Anthocyanin, antioxidant activity, chlorogenic acid, on-line HPLC-ABTS method, phenolic compound, Vaccinium corymbosum L.