Phenolic content and antioxidant capacity of fruits of plum cv. 'stanley' (Prunus domestica L.) As influenced by maturity stage and on-tree ripening

Abstract

Fruits of plum 'Stanley' were analysed for total anthocyanins, total phenolics and antioxidant capacity over three successive harvest years. Fresh fruits were harvested five times per year. The total anthocyanins content ranged from 5 to 57 mg/100 g, expressed as cyanidin-3-glucoside equivalents, on a fresh-weight basis. The anthocyanin concentrations were higher in fruits of successive harvesting dates, meaning that anthocyanin accumulation seemed to occur constantly during fruit development and ripening. The total phenolic content was within the range of 70 to 214 mg gallic acid equivalents/100 g fresh weight. The highest concentrations of anthocyanins and phenolics were observed in plum fruits harvested in 2009, which is most likely due to the favourable weather conditions. The free radical galvinoxyl was used to evaluate antioxidant capacity of plum fruits. The total antioxidant capacity of fresh fruits, expressed as the rate constant k1', ranged from 0.950 to 3.010 s-1. Antioxidant capacity also strongly depended on ripening stage, showing completely opposite trend compared to that of total phenolics. Since total phenolics and antioxidant capacity performed nearly 'object and its reflection in the mirror' trend, consequently the lowest antioxidant capacity was observed in plum fruits harvested in 2009.