Total polyphenols, catechin profiles and antioxidant activity of tea products from purple leaf coloured tea cultivars L.C. Kerio a , F.N. Wachira b,⇑ , J.K. Wanyoko a , M.K. Rotich c a Tea Research Foundation of Kenya, P.O. Box 820, 20200 Kericho, Kenya b Association for Strengthening Agricultural Research in East and Central Africa (ASARECA), P.O. Box 765, Entebbe, Uganda c Egerton University, Chemistry Department, P.O. Box 536, Egerton, Kenya article info Article history: Received 19 March 2012 Received in revised form 23 August 2012 Accepted 19 September 2012 Available online 28 September 2012 Keywords: Total polyphenol Catechins Caffeine Tea Antioxidant activity abstract Black (aerated) and green (unaerated) tea products, processed from 10 green and 18 purple leaf coloured cultivars of Kenyan origin, and two tea products, from the Japanese cultivars, Yabukita and Yutakamidori, were assayed for total polyphenols (TP) content, individual catechin profiles and in vitro antioxidant capacity (AA). In addition, the phenolic content of the tea products was determined using the Folin– Ciocalteu phenol reagent. Catechin fractions were identified using reverse phase high performance liquid chromatography (HPLC) with a binary gradient elution system. The AA% of the tea products was determined using a 2,2 0 -diphenyl picrylhydrazyl (DPPH) radical assay method. The results showed that TPs, catechin profiles and antioxidant activities were significantly (p 6 0.05) higher in unaerated than in aerated teas. Tea products from the purple leaf coloured tea cul- tivars had levels of TPs, total catechin (TC) and antioxidant activities similar to those from the green leaf coloured cultivars, except for teas from the Japanese cultivars that were very low in the assayed param- eters. Caffeine content was significantly (p 6 0.05) lower in products from the purple leaf coloured cul- tivars than in those from the green leaf coloured tea cultivars. Antioxidant activity (%) was higher in tea products from the Kenyan germplasm than in those from the Japanese cultivars. Antioxidant potency of tea products was significantly (r = 0.789 // , p 6 0.01) influenced by the total anthocyanin content of the purple leaf coloured cultivars. Cyanidin-3-O-glucoside was the anthocyanin most highly correlated with AA% (r = 0.843 // , p 6 0.01 in unaerated tea). Total catechins in the unaerated products from the green leaf coloured tea cultivars were also significantly correlated with antioxidant capacity (r = 0.818 // , p 6 0.01). Results from this study suggest that the antioxidant potency of teas is dependent on the predominant fla- vonoid compound, the type of tea cultivar and the processing method. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction Worldwide, aerated (black) and unaerated (green) products are the most widely consumed types of teas, though tea processing has diversified to the production of several specialty types of products (Reeves, Owuor, & Othieno, 1987). Aerated and unaerated teas are both processed from the tender shoots of the tea plant. The quality of the processed product depends on the chemical composition of the tea shoots and the manufacturing technique employed. Unaerated tea contains significant quantities of the unoxidised catechins: (catechin (+)-C, ()-epicatechin (EC), ()-epigallocate- chin (EGC), ()-epigallocatechin gallate (EGCG), ()-gallocatechin (GC), ()-epicatechin gallate (ECG) and ()-gallocatechin gallate (GCG); the oxidised derivatives of the catechins, theaflavins (TFs) and thearubigins (TRs), are found in fully aerated and semi-aerated (Oolong) teas. In addition, tea also contains amino acids (theanine, gamma amino butyric acid), carbohydrates, proteins, minerals, trace elements, volatile compounds, carotenoids and alkaloids, namely caffeine, theophylline and theobromine. Initiatives to develop specialty teas have been driven by the de- sire to provide more healthful tea products. Indeed, some specialty tea products have been demonstrated to be more pharmacologi- cally active owing to their high levels of biologically active mole- cules. Some of these specialty teas are made even more appealing to the consumer by addition of colour additives and fla- vours. Examples of such teas include white tea, flavoured teas (gin- ger, lemongrass, lemon, vanilla, strawberry), scented tea, herbal teas and decaffeinated teas. Other types of tea products are pro- duced by process modification, such are black and green teas en- riched with anthocyanins, the amino acid theanine, specific catechins, for example epigallocatechin gallate (EGCG), and gamma 0308-8146/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.foodchem.2012.09.066 ⇑ Corresponding author. Tel.: +256 0722 644279; fax: +256 414 321126. E-mail address: fwachira@yahoo.com (F.N. Wachira). Food Chemistry 136 (2013) 1405–1413 Contents lists available at SciVerse ScienceDirect Food Chemistry journal homepage: www.elsevier.com/locate/foodchem