Paper Presenter: Deena Ramful, Department of Biosciences, Faculty of Science, University of Mauritius
Citrus fruits are of great interest mainly because of the health-promoting potential ascribed to their high concentrations of vitamin C and phenolics. Peels of citrus fruits have potential application in the food and pharmaceutical industries whilst citrus pulps can be processed into juices with multiple health benefits. Several varieties of citrus fruits are grown in Mauritius and represent a prospective source of natural antioxidants. In this context, twenty-one varities of locally grown citrus fruits were screened for their vitamin C and phenolics contents. Furthermore, the antioxidant activities of the fruit extracts were assessed using three established in vitro assays namely, the Trolox equivalent antioxidant capacity (TEAC), ferric reducing antioxidant power (FRAP) and the scavenging of hypochlorous acid (HOCl) assays. The vitamin C, total phenolic and flavonoid contents of the extracts decreased in the following order: flavedo > albedo > pulp extracts. Total phenolics correlated strongly with the TEAC, FRAP and HOCl data for the flavedo, albedo and pulp extracts (r = 0.65 – 0.95). The total flavonoids levels also showed good influence on the antioxidant capacities of the flavedo and albedo extracts (r = 0.62 – 0.77). A very low negative correlation was obtained between ascorbate levels and antioxidant potential of the flavedo extracts. Vitamin C levels showed moderate to low correlations with regards to the antioxidant activities of the pulp extracts (r = 0.17 – 0.47). The phytochemical composition of the extracts was found to vary as a function of date of harvest for some citrus fruit varieties. Based on the results obtained from the antioxidant assays, nine different flavedo, albedo and pulp extracts, with highest antioxidant capacities, were chosen for analysis of their flavonoid glycosides by HPLC. The levels of one flavonol glycoside (rutin), three flavone glycosides (diosmin, rhoifolin and isorhoifolin) and seven flavanone glycosides (neoeriocitrin, poncirin, narirutin, neohesperidin, didymin, hesperidin and naringin) were assayed in flavedo and albedo extracts of orange, clémentine, mandarine, tangor, tangelo and pamplemousses varieties and in pulp extracts of orange, mandarin, tangor, tangelo, kumquat, calamondin and pamplemousses varieties. These were identified as promising candidates for the development of a citrus-based functional food geared towards the mangement of ROS-mediated disorders. However, prior to such application, their in vivo activities would have to be fully assessed using cellular and animal experimental models and eventually clinical trials.
Keywords: Citrus fruits, phenolics, flavonoids, vitamin C, antioxidant capacity, TEAC, FRAP, functional food