Please cite this article in press as: Ramful, D., et al., Bioactive phenolics and antioxidant propensity of flavedo extracts of Mauritian citrus fruits: Potential prophylactic ingredients for functional foods application. Toxicology (2010), doi:10.1016/j.tox.2010.01.012 ARTICLE IN PRESS G Model TOX-50515; No. of Pages 13 Toxicology xxx (2010) xxx–xxx Contents lists available at ScienceDirect Toxicology journal homepage: www.elsevier.com/locate/toxicol Bioactive phenolics and antioxidant propensity of flavedo extracts of Mauritian citrus fruits: Potential prophylactic ingredients for functional foods application Deena Ramful a , Theeshan Bahorun b,∗ , Emmanuel Bourdon c , Evelyne Tarnus c , Okezie I. Aruoma d a Department of Agricultural and Food Science, Faculty of Agriculture, University of Mauritius, Réduit, Mauritius b Department of Biosciences, Faculty of Science, University of Mauritius, Réduit, Mauritius c Laboratoire de Biochimie et Génétique Moléculaire (LBGM), Groupe d’Etude sur l’Inflammation Chronique et l’Obésité (GEICO), Université de Saint Denis de La Réunion, France d Department of Pharmaceutical and Biomedical Sciences, Touro College of Pharmacy, New York, USA article info Article history: Received 26 November 2009 Received in revised form 11 January 2010 Accepted 18 January 2010 Available online xxx Keywords: Citrus fruits Flavedo Flavonoids Vitamin C Antioxidants Food ingredients Functional foods abstract The flavedo extracts of twenty-one varieties of citrus fruits (oranges, satsumah, clementine, mandarins, tangor, bergamot, lemon, tangelos, kumquat, calamondin and pamplemousses) grown in Mauritius were examined for their total phenolic, flavonoid and vitamin C contents and antioxidant activities. Total phenolics correlated strongly with the trolox equivalent antioxidant capacity (TEAC), ferric reducing antioxidant capacity (FRAP) and hypochlorous acid (HOCl) scavenging activity assays (r > 0.85). Based on their antioxidant activities in these three assays nine citrus fruits namely, one orange, clementine, tangor and pamplemousse variety, two tangelo varieties and three mandarin varieties, were further characterized for their flavanone, flavonol and flavone levels by HPLC and their antioxidant activities were assessed by the copper-phenanthroline and iron chelation assays. The flavanone, hesperidin, was present at the highest concentrations in all flavedo extracts except for pamplemousses where it was not detected. Contents in hesperidin ranged from 83 ± 0.06 to 234 ± 1.73 mg/g FW. Poncirin, didymin, diosmin, isorhoifolin and narirutin were also present in all extracts whereas naringin was present only in one mandarin variety. The nine flavedo extracts exhibited good DNA protecting ability in the cuphen assay with IC 50 values ranging from 6.3 ± 0.46 to 23.0 ± 0.48 mg FW/mL. Essentially the flavedos were able to chelate metal ions however, tangor was most effective with an IC 50 value of 9.1 ± 0.08 mg FW/mL. The flavedo extracts of citrus fruits represent a significant source of phenolic antioxidants with potential prophylactic properties for the development of functional foods. © 2010 Elsevier Ireland Ltd. All rights reserved. 1. Introduction The role played by dietary factors on health status has long been recognised but it has been only recently that epidemiological and clinical studies have provided a clearer insight on the chemical and physiological mechanisms of the effects of bioactive foods on human health (Shahidi, 2009). Phytophenolics play a crucial role in health promotion and disease prevention by mechanisms related to cell differentiation, deactivation of pro-carcinogenes, maintenance of DNA repair, inhibition of N-nitrosamine formation and change of estrogen metabolism, amongst others (Shahidi, 2004). Major mechanisms for the antioxidant effect of phenolics in functional foods include free radical scavenging and metal chelation activi- ties. Reactive oxygen species (ROS), such as the superoxide radical (O 2 •- ), hydrogen peroxide (H 2 O 2 ), hypochlorous acid (HOCl) and the hydroxyl radical (HO • ) have been recognised to play a determin- ∗ Corresponding author. E-mail address: tbahorun@uom.ac.mu (T. Bahorun). ing role in the pathogenesis of several human diseases (Halliwell, 1996; Halliwell et al., 1992; Aruoma, 1994, 2003). ROS-induced oxidation can result in cell membrane disintegration, membrane protein damage and DNA mutation, which can further initiate or propagate the development of diseases including cancer (Huang et al., 2001), diabetes (Boynes, 1991), neurodegenerative diseases (Perry et al., 2000), the process of aging (Hensley and Floyd, 2002) and cardiovascular dysfunctions (Hool, 2006). Phenolic compounds such as phenolic acids, flavonoids, stilbenes, tannins and lignans can scavenge free radicals and quench ROS and therefore provide effective means for preventing and treating free radical-mediated diseases. Mauritius is a tropical island in the Indian Ocean with a relatively high prevalence of cardiovascular diseases, cancers and diabetes (Central Statistic Office, 2007). This has triggered interest in the study of the phytochemistry and antioxidant capacity of the Mauri- tian diet, which comprises a wide variety of exotic fruits, vegetables and beverages (Luximon-Ramma et al., 2003; Bahorun et al., 2004, 2007, this issue). Citrus (Citrus L. from Rutaceae) is one of the most popular world fruit crops that, besides providing an ample sup- 0300-483X/$ – see front matter © 2010 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.tox.2010.01.012