Tea and herbal infusions: Their antioxidant activity and phenolic profile Ali K. Atoui a , Abdelhak Mansouri a , George Boskou b,1 , Panagiotis Kefalas a, * a Laboratory of Chemistry of Natural Products, Mediterranean Agronomic Institute of Chania (MAICh), P.O. Box 85, 73100 Chania, Greece b Department of Nutrition–Dietetics, Harokopio University, El Venizelou 70, Kallithea 17671, Athens, Greece Received 24 November 2003; received in revised form 28 January 2004; accepted 28 January 2004 Abstract Tea and herbal infusions have been studied for their polyphenolic content, antioxidant activity and phenolic profile. The total phenolics recovered by ethyl acetate from the water extract, were determined by the Folin–Ciocalteu procedure and ranged from 88.1 ± 0.42 (Greek mountain tea) to 1216 ± 32.0 mg (Chinese green tea) GAE (Gallic acid equivalents)/cup. The antioxidant activity was evaluated by two methods, DPPH and chemiluminescence assays, using Trolox and quercetin as standards. The EC 50 of herbal extracts ranged from 0.151 ± 0.002 mg extract/mg DPPH (0.38 quercetin equivalents and 0.57 Trolox equivalents), for Chinese green tea, to 0.77 ± 0.012 mg extract/mg DPPH (0.08 quercetin equivalents and 0.13 Trolox equivalents), for Greek mountain tea. Chemiluminescence assay results showed that the IC 50 ranged from 0.17 ± 3.4 · 10 3 lg extract/ml of the final solution in the measuring cell (1.89 quercetin and 5.89 Trolox equivalents) for Chinese green tea, to 1.10 ± 1.86 · 10 2 g extract/ml of the final solution in the measuring cell (0.29 quercetin and 0.90 Trolox equivalents) for Greek mountain tea. The phenolic profile in the herbal infusions was investigated by LC-DAD-MS in the positive electrospray ionization (ESI þ ) mode. About 60 different flavo- noids, phenolic acids and their derivatives have been identified. Ó 2004 Elsevier Ltd. All rights reserved. Keywords: Antioxidant activity; Flavonoids; Phenolic acids; LC–MS; Herbal infusion; Tea 1. Introduction An antioxidant can be defined as any substance that when present at low concentrations compared to that of an oxidizable substrate, significantly delays or inhibits the oxidation of that substrate (Percival, 1998; Young & Woodside, 2001). The physiological role of free radical- and hydroxyl free radical-scavengers, as this definition suggests, is to prevent damage to cellular components arising as a consequence of chemical reactions involving free radicals. In recent years, a substantial body of evi- dence has indicated a key role for free radicals as major contributors to aging and to degenerative diseases of aging, such as cancer, cardiovascular disease, cataracts, immune system decline, and brain dysfunction (Ames, Shigenaga, & Hagen, 1990; Percival, 1998; Young & Woodside, 2001). Fortunately, free radical formation is controlled naturally by various beneficial compounds known as antioxidants (Percival, 1998). When the availability of antioxidants is limited, this damage can become cumulative and debilitating oxidative stress re- sults (Swanson, 1998). Antioxidants are capable of sta- bilizing, or deactivating free radicals before the latter attack cells and biological targets. They are therefore critical for maintaining optimal cellular and systemic health and well-being (Percival, 1998) (see Figs. 1 and 2). Many research groups are examining the chemical nature and activity of natural antioxidants in fruits, vegetables, grains, herbs and other foods (Larson, 1988; Shahidi, 2000). Most antioxidants isolated from higher plants are polyphenols, which show biological activity as * Corresponding author. Tel.: +30-28210-35056; fax: +30-28210- 35001. E-mail address: panos@maich.gr (P. Kefalas). 1 Present address: Department of Nutrition–Dietetics, Harokopio University, El Venizelou 70, Kallithea 17671, Athens, Greece. 0308-8146/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.foodchem.2004.01.075 Food Chemistry 89 (2005) 27–36 www.elsevier.com/locate/foodchem Food Chemistry