Assessment of the polyphenolic composition of the organic extracts of Mauritian black teas: A potential contributor to their antioxidant functions

Issue title: Free Radicals in Biology and Medicine: From Inflammation to Biotechnology

Article type: Research Article

Authors: Luximon-Ramma, Amitabye | Neergheen, Vidushi S. | Bahorun, Theeshan | Crozier, Alan | Zbarsky, Virginia | Datla, Krishna P. | Dexter, David T. | Aruoma, Okezie I.

Affiliations: Department of Biosciences, Faculty of Science, University of Mauritius, Réduit, Republic of Mauritius | Plant Products and Human Nutrition Group, Graham Kerr Building, Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, UK | Department of Cellular and Molecular Neuroscience, Division of Neuroscience and Psychological Medicine, Imperial College London, Charing Cross Hospital Campus, Fulham Palace Road, London W6 8RF, UK | Faculty of Health and Social Care, London South Bank University, Borough Road, London SE1 0AA, UK

Note: [] Corresponding authors: Dr. Theeshan Bahorun, Department of Biosciences, Faculty of Science, University of Mauritius, Réduit, Mauritius. E-mail: tbahorun@uom.ac.mu. Dr. Okezie I. Aruoma, Faculty of Health and Social Care, London South Bank University, Borough Road, London SE1 0AA, UK. E-mail: aruomaoi@lsbu.ac.uk; aruomaoi@oicainternational.co.uk

Abstract: There is increasing interest in the emerging view that tea improves the antioxidant status in vivo and thereby helps to lower risk of certain types of cancer, coronary heart disease and stroke and its component biofactors could provide prophylactic potential for these diseases. The polyphenolic composition and the antioxidant properties of organic extracts (acetone/methanol) of Mauritian commercial black teas were evaluated. HPLC data of the individual compounds revealed remarkably high levels (+)-Catechin ((+)-C), (−)-epicatechin ((−)-EC), (−)-epicatechin 3-gallate ((−)-ECG), (−)-epigallocatechin ((−)-EGC), (−)-epigallocatechin 3-gallate ((−)-EGCG) and gallic acid. Analysis of hydrolysed extracts indicated that quercetin was the dominant flavonol aglycone with traces of myricetin and kaempferol. Based on the Ferric Reducing Antioxidant Power (FRAP) and the Trolox Equivalent Antioxidant Capacity (TEAC) assays Extra tea from Bois Chéri exhibited the highest antioxidant potential. Linear regression analyses showed that the antioxidant capacities of the organic extracts are strongly influenced by total phenols (TEAC: r=0.95 and FRAP: r=0.96) and to a lesser extent by total proanthocyanidin and total flavonoid contents. Catechins and gallic acid seem to add up to the overall antioxidant capacity of black tea extracts. The fresh tea leaves had high levels of total phenols, total flavonoids, total proanthocyanidin and exhibited greater antioxidant potential when compared with black teas. Organic extracts of endemic teas represent useful source of phenolic antioxidants supplements for prophylactic use.

Keywords: Black teas, dietary antioxidants, organic tea extracts, total phenols, flavonoids, proanthocyanidins, catechins, cancer, coronary heart disease and stroke

Journal: BioFactors, vol. 27, no. 1-4, pp. 79-91, 2006