Copyright © 2006 John Wiley & Sons, Ltd. Phytother. R Antioxidant Screening of Medicinal Herbal Teas Hernán Speisky 1,2 *, Claudia Rocco 1,2 , Catalina Carrasco 1,2 , Eduardo A. Lissi 3 and Camilo López-Alarcón 3,4 1 Micronutrients Unit, Nutrition and Food Technology Institute and Faculty Chemical and Pharmaceutical Sciences; University of Chile, Santiago, Chile 2 Department of Analytical Pharmacological and Toxicological Chemistry, Faculty Chemical and Pharmaceutical Sciences; University of Chile, Santiago, Chile 3 Department of Chemistry, Faculty of Chemistry and Biology, University of Santiago, Santiago, Chile 4 Pharmacy Department, Faculty of Chemistry, Catholic University, Santiago, Chile Herbal tea consumption is deeply and widely rooted amongst South-American populations. In view of the involvement of oxygen- and nitrogen-reactive species in the ethiogenesis of several diseases, the antioxidant properties of some of the herbal teas most commonly consumed in the southern regions was assessed in vitro. Around one-third of the 13 examined herbs, displayed a substantially higher ability to scavenge ABTS +· radicals (TEAC assay), and to quench the pro-oxidant species, hypochlorite (HClO) and peroxynitrite (ONOO - ). Amongst the tested herbs, teas prepared from Haplopappus baylahuen, Rosa moschata and Peumus boldus showed the highest TEAC and HClO-quenching activities. These herbs were around 5- to 7-fold more potent than the least active herbs. Based on the TEAC assay, 150 mL of tea prepared from H. baylahuen, R. moschata and P. boldus would be equivalent to around 200 mg of Trolox ® . Teas from H. baylahuen and P. boldus were also found to be particularly potent in quenching HClO. In the ONOO - assay, H. baylahuen and Buddleia globosa showed the highest activities. The results obtained suggest that the regular consumption of teas prepared from some of these herbs may be useful potentially to provide the organism with molecules capable of protecting the gastrointestinal tract against certain pathologically relevant oxidant species. Keywords: herbal teas; antioxidants; free radicals; hypochlorite; peroxynitrite. * Correspondence to: Dr H. Speisky, Micronutrients Unit, Nutrition and Food Technology Institute (INTA), University of Chile, POB 138-11, Santiago, Chile. E-mail: hspeisky@inta.cl an important source of potentially health-protecting antioxidants (Higashi-Okai et al., 2001; Wu et al., 2003; Higdon and Frei, 2003) and world-wide represent the most popular form of daily herb consumption. More recently, the study of other herbs as a potential source of antioxidants has also stemmed from the need to screen endangered floras, and has been prompted by the increasing assumption that, given their natural origin, plant-derived antioxidants would comprise a group of relatively innocuous compounds. The consumption of herbs in the form of herbal teas represents a widely established habit and the most popu- lar form of herb consumption amongst people in South America (Jagtenberg and Evans, 2003). Particularly, in Chile, the term ‘agüita’, refers to an after-meal aque- ous solution prepared, at the table, by the simple addi- tion of a small amount of the leaves (and exceptionally bark) from an herb to a cup containing hot (near- boiling) water (Montes and Wilkomirsky, 1985). Herbs consumed in such form correspond mostly to plants to which some mild medicinal or digestive properties have been vernacularly attributed (Evans, 2002). Despite its widespread use, however, in most cases no scientific assessment of these claims has been conducted. Con- sidering the increasing recognition that antioxidant consumption may play a role in preventing several oxidative-stress related diseases, the present study was undertaken to evaluate the antioxidant potential of the main herbal teas consumed in Chile. The study comprised an array of herbs, both endemic as well as INTRODUCTION The consumption of fruits and vegetables is strongly and inversely associated with the incidence and/or mortality rate of several forms of cancer, cardiovas- cular, cerebro-vascular and neuro-degenerative diseases (Bazzano et al., 2003; Liu, 2003; Riboli and Norat, 2003). Since the occurrence of oxidative stress can either lead to or accompany the progression of the above disor- ders, the high presence of antioxidants in fruits and vegetables generally has been regarded as an impor- tant basis for the health-protecting effects associated with their consumption (Gate et al., 1999; Terry et al., 2001). In addition to fruits and vegetables, herbs of no particular nutritional value can also constitute an im- portant source of antioxidants (Warren, 1999; Ng et al., 2000). The term herb refers not only to herbaceous plants, but also to the leaves, bark, roots, seeds, fruits and flowers of shrubs and trees. The leaves from black and green tea (Camellia sinensis), long used amongst western and Asian populations, respectively, constitute