Variation in the content of bioactive flavonoids in different brands of orange and grapefruit juices

Citrus flavonoids have been shown to possess biological activities such as anti-inflammatory properties, cholesterol lowering and immune system modulation. In this study, 12 made-from-concentrate (MFC) and 14 not-from-concentrate (NFC) orange juices, and five NFC grapefruit juices available in the US market were analyzed for their flavonoid content by reverse phase HPLC. Individual and total flavonoid content was determined for all of the brands. The correlation between flavonoid content (mg) and price (US dollar) per unit volume of orange and grapefruit juices were also evaluated. Significant differences (P ≤ 0.05) among the brands and within the brand were observed for all of the prominent flavanone glucosides. Within the brand, juice types containing added antioxidant vitamins C and E were not superior in flavonoid content compared to orange juice types devoid of added antioxidant vitamins. Total flavonoid content of MFC orange juices (53 mg/100 mL; n = 12) was significantly (P ≤ 0.05) higher than NFC orange juices (36.5 mg/100 mL; n = 14). Hesperidin was found to be the major flavonoid followed by narirutin and didymin in orange juice. Naringin, narirutin, and poncirin were the major flavonoids in all brands of grapefruit juices. The concentration of didymin was considerably higher in NFC orange juices compared to MFC orange juices. Interestingly, no correlation was observed between price and the total flavonoid content of MFC orange juices and NFC grapefruit juices. However, a significant negative correlation (r = - 0.49 ; P = 0.001) was observed for NFC orange juices. This study provides valuable information on flavonoid composition of orange and grapefruit juices commonly available in the US market.