Polyphenol composition, vitamin C content and antioxidant capacity of Mauritian citrus fruit pulps

Abstract

The pulp extracts of twenty-one varieties of citrus fruits (oranges, satsumah, clementine, mandarins, tangor, bergamot, lemon, tangelos, kumquat, calamondin and pamplemousses), commonly grown in Mauritius, were characterised in terms of their total soluble solids (TSS), titratable acidity (TA), polyphenol composition and vitamin C contents. Total phenolics ranged from 406.3±14 to 1694±19μgg−1 fresh weight (FW). Total flavonoids varied between 133±6 and 965±7μgg−1 FW and vitamin C contents were from 166±19μg/mL to 677±22μg/mL. The pulp of a pamplemousse variety had the highest TSS/TA ratio whereas lemon pulps had lowest TSS/TA ratios. The antioxidant activities of the pulp extracts were assessed and total phenolics correlated strongly with the trolox equivalent antioxidant capacity (TEAC), ferric reducing antioxidant capacity (FRAP) and hypochlorous acid (HOCl) scavenging activity assays. Based on their antioxidant activities, nine citrus fruits namely, one orange, tangor, kumquat, calamondin and pamplemousse variety and two mandarin and tangelo varieties were further characterised for their flavanone, flavonol and flavone levels by HPLC. Hesperidin (6.89±0.06 to 26.98±0.07mg/g FW) and narirutin (0.27±0.01 and 20.91±0.10mg/g FW) were present at high concentrations compared to the other flavonoid glycosides in the pulp extracts. Naringin was detected only in pulp extracts of pamplemousses. In the light of the data obtained, citrus fruit pulps represent an important source of phytochemicals with potent antioxidant capacity.