Characterisation of the flavonoid composition and total antioxidant capacity of juice from different citrus varieties from the Western Cape region

Four citrus varieties, clementine mandarin, satsuma mandarin, navel orange and Valencia orange, grown in the Western Cape of South Africa, were evaluated in terms of their total polyphenol content (TPC), total flavonoid content (TFC), major phenolic compounds and total antioxidant capacity (TAC) of the juice, taking into account seasonal variation (2011, 2012 and 2014). The results indicated that juice from satsuma mandarin had the highest TFC level (748 mg/L naringin equivalents) and Valencia orange had the lowest TPC (115 mg/L gallic acid equivalents). The data indicated that varieties grown in the same geographical region differed in terms of TPC and TFC content of the juice and that seasonal influence was not significant. Contrary to these results, the major phenolic compounds showed great variation between different seasons. Hesperidin and narirutin were the predominant flavanone-C-glycosides in navel orange and Valencia orange juice, with vicenin-2 and ferulic acid-O-hexoside also present in high quantities. The juice from satsuma mandarin had the highest quercetin-3-O-rutinoside-7-O-glucoside, narirutin and rutin concentrations, whilst clementine mandarin had the lowest in terms of the sum of individual phenolic compounds quantified. Overall the citrus fruit juice samples, collected in 2014, irrespective of variety, had the highest TAC.