Research Article Received: 13 October 2011 Revised: 2 January 2012 Accepted: 4 January 2012 Published online in Wiley Online Library: (wileyonlinelibrary.com) DOI 10.1002/jsfa.5611 Screening of the antioxidant properties and polyphenol composition of aromatised green tea infusions Anna Pe ¸ kal, Paulina Dr ´ o ˙ zd ˙ z, Magdalena Biesaga and Krystyna Pyrzynska * Abstract BACKGROUND: Aromatised green teas are widely sold and popular owing to their fragrance. In this study the antioxidant activity of six commercial green tea infusions was assessed by three complementary assays. RESULTS: In order to evaluate the tea infusions as antioxidant sources, their phenolic content (Folin-Ciocalteu assay), cupric ion- reducing antioxidant capacity (CUPRAC) and 2,2-diphenyl-1-picryhydrazyl (DPPH) radical-scavenging ability were determined. Their content of polyphenols was also determined by high-performance liquid chromatography/mass spectrometry (HPLC/MS) in negative electrospray ionisation mode. Some teas with citrus aroma, besides having a relatively high content of catechins, also contain other phenolic compounds such as naringin and hesperidin. The three assays used to evaluate the antioxidant capacity of the tea infusions gave different rank orders. Therefore an antioxidant index was calculated for better correlation of the results, and its highest value was obtained for Clear Green Mint tea infusion. CONCLUSION: The studied teas, besides having a relatively high content of catechins, also contain naringin and hesperidin, which are not present in ‘pure’ green tea. It is important to run multiple assays to get a better estimate of the antioxidant capacity of a given sample. c  2012 Society of Chemical Industry Keywords: aromatised green tea; polyphenols; reducing power; scavenging ability; antioxidant index INTRODUCTION Tea is one of the most commonly consumed beverages worldwide. Green tea, like black and oolong teas, is manufactured from dried leaves of Camellia sinensis. It differs from other types of tea in its processing method as well as its organoleptic taste, flavour and chemical content. To produce green tea, freshly harvested leaves are steamed to prevent fermentation, yielding a dry, stable product. Polyphenols are the most abundant compounds in tea leaves and extracts and are primarily responsible for the beneficial healthful properties of tea. Green tea, which accounts for 20% of world consumption, is characterised by the presence of large amounts of flavan-3-ols, also known as catechins. The content of catechins varies with climate, season, horticultural practices, leaf age and variety. Flavonols, including quercetin, kaempferol, myricetin and their glycosides, are also present in tea. A number of different health benefits have been attributed to green tea, including prevention and/or control of atheroscle- rosis, hypertension, coronary heart disease, diabetes, metabolic syndrome, obesity and cancer as well as antibacterial, antiviral and antifungal activities. 1–3 Antioxidant properties of flavonoids are manifested particularly by their ability to inhibit free rad- ical generation, scavenge free radicals and chelate transition metal ions, mainly Fe and Cu, which are catalysts of free rad- ical reactions. Polyphenols also prevent the generation of free radicals by inhibiting the activity of existing enzymes participat- ing in their generation or by increasing the activity of enzymes with antioxidant properties, probably via the induction of protein molecule biosynthesis. 4,5 There is great interest in the quantification of antioxidants and the determination of antioxidant capacities of a number of specific food compounds. Many methods have been developed for these purposes. 6–8 They differ from each other in terms of reaction mechanisms, oxidant and target/probe species, reaction conditions and expression of results. Antioxidant capacity, which is related to compounds capable of protecting a biological system against the potentially harmful effects of processes or reactions, can be determined according to several factors, so it must be specified which factor is being measured by the particular method employed. Spectrophotometric methods for the evaluation of antioxidant properties of food samples are still the most widely used, because reagents are easy to obtain, results are given quickly and experiments are convenient. However, some weaknesses of spectrophotometric methods should also be realised. For example, the total quantities of polyphenols in tea samples as well as the proportions of individual compounds vary with tea variety and tea plant growth conditions. Besides, every individual component has ∗ Correspondence to: Krystyna Pyrzynska, Department of Chemistry, University of Warsaw, Pasteura 1, PL-02-093 Warsaw, Poland. E-mail: kryspyrz@chem.uw.edu.pl Department of Chemistry, University of Warsaw, Pasteura 1, PL-02-093 Warsaw, Poland J Sci Food Agric (2012) www.soci.org c  2012 Society of Chemical Industry