The effects of preharvest methyl jasmonate (MJ) application on fruit quality, flavonoid content and antioxidant capacity (ORAC) in black raspberry cv. Jewel (Rubus occidentalis L) were studied under field conditions. Raspberries treated with 0.1 mm methyl jasmonate had 20% higher soluble solids content, 20% higher total sugars, 16% higher fructose, 34% higher glucose and 30% lower titratable acids, 31% lower malic acid and 17% lower citric acid than untreated fruit. El-lagic acid, quercetin 3-glucoside, kaempferol 3-glucoside, kaempferol 3-glucuronide, cyanidin 3-glucoside and cyaniding 3-rutinoside were found in raspberry fruit extract. Cyanidin 3-rutinoside was the most dominant anthocyanin and was the major contributor to antioxidant activity in Jewel raspberries. MJ treatments significantly enhanced the content of anthocyanins by 92%, total phenolics by 53%, flavonoids by 98% and the antioxidant capacities by 74% in the fruit. The ORAC value was positively correlated with anthocyanins and total phenolics. In this study, the correlation coefficient for ORAC (y) vs anthocyanins (x) was 0.977 (y = 0.056x + 27.874), and that for ORAC (y) vs. total phenolics (x) was 0.988.
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