Antioxidant Activity in Common Beans (Phaseolus vulgaris L.) § ANABERTA CARDADOR-MARTI ÄNEZ, ² GUADALUPE LOARCA-PIN ˜ A, ² AND B. DAVE OOMAH* ,‡ Programa de Posgrado en Alimentos del Centro de la Repu ´blica (PROPAC), Research and Graduate Studies in Food Science, School of Chemistry, Universidad Auto ´noma de Quere ´taro, Quere ´taro, Qro., 76010 Mexico, and National Bioproducts and Bioprocesses Program, Pacific Agri-Food Research Centre, Agriculture and Agri-Food Canada, Summerland, British Columbia, Canada V0H 1Z0 Beans were pearled to evaluate the feasibility of increasing antioxidant activity and phenolic antioxidants. Phenolics were concentrated mostly in the hull fraction at about 56 mg of catechin equivalents per gram of sample. The methanolic extracts of the pearled bean samples were screened for antioxidant potential using the -carotene-linoleate and the 1,1-diphenyl-2-picrylhydrazyl (DPPH) in vitro model systems. The pearled material, also referred to as milled samples, exhibited antioxidant activity that correlated with phenolic content and inhibited DPPH significantly in a dose-dependent manner. Phenolics and antioxidant activities were also examined in chromatographic fractions of methanolic extracts of manually obtained hulls that represented a model used previously to ascertain antimutagenic activity. Fractions extracted with ethyl acetate/acetone and acetone displayed antioxidant activity, which implies potent free radical scavenging activity with antimutagenic activity. KEYWORDS: Phenolics; antioxidant activity; -carotene; DPPH; pearling; dry milling; beans INTRODUCTION Dry beans, a staple food in many Latin American countries, are receiving increasing attention as a functional food. Con- sumption of dry beans has been linked to reduced risk of diabetes and obesity (1) because of the markedly alternating effects on blood sugar and insulin response and thereby their potential use for prevention and control of diabetes (2). The inhibitory role of dry beans in reduction of coronary heart disease has also been noted (3) and confirmed recently (4). The study by Hughes et al. (5) provides experimental data to support existing epidemiological research linking high levels of dry bean consumption with reduced colon cancer risk. It is becoming clear that beans, as a source of dietary fiber, regulate gastric emptying and thus the rate of digestion and absorption, prolong the postprandial presence of intestinally derived lipoprotein, and augment the gastrointestinal response in humans (6). The physiological effects of dry bean consumption may be due to the presence of abundant phytochemicals including polyphenolics, which possess both anticarcinogenic and anti- oxidant properties. It is generally believed that antioxidants scavenge free radicals and reactive oxygen species and can be extremely important in inhibiting oxidative mechanisms that lead to degenerative diseases. Bean extracts, especially from the hulls, are known to possess antioxidant activity. Thus, the crude methanolic extract of peas showed strong antioxidant activity due to the presence of pH-dependent pigments (7, 8). A freeze- dried navy bean hull extract evaluated in storage studies with soy and sunflower oils showed stronger antioxidant activity than a BHA-BHT mixture (9). Mung bean hulls possess antioxidant activity, which has reducing power, scavenge DPPH radicals, and inhibit lipid peroxidation and nonlipid oxidative damage (10, 11). Our previous studies (12, 13) showed that bean hulls contained large amounts of phenolic compounds, and their methanolic extract exhibited substantial antimutagenic activity against Salmonella typhimurium and aflatoxin B 1 . This anti- mutagenic activity that involves formation of complexes between phenolic compounds and mutagens may apparently be mediated by the scavenging activity of the phenolics. Therefore, one of the objectives of this study was to evaluate the antioxidant activity of the methanolic extracts of bean hulls that served as a model previously to ascertain antimutagenic activities (12, 13). Since the hull is rich in phenolics, a simple pearling method was used to obtain hulls and other bean fractions for subsequent assessment of their phenolics and antioxidant activities. Infor- mation on antioxidant activity will increase the understanding of the function of bean products in the diet to reduce chronic diseases. MATERIALS AND METHODS Dry beans (Phaseolus Vulgaris cv. Flor de Mayo FM-38, red testa), grown and harvested in 2001, were kindly provided by Instituto Nacional de Investigaciones Forestales Agricolas y Pecuarias (INIFAP, Mexico). This cultivar was used in our previous studies (12, 13) and was selected because it is preferred for consumption in the central region of Mexico. § Pacific Agri-Food Research Centre Contribution No. 2181. * To whom correspondence should be addressed [phone (250) 494-6399, fax (250) 494-0755, E-mail oomahd@agr.gc.ca]. ² Universidad Auto ´noma de Quere ´taro. ‡ Agriculture and Agri-Food Canada. J. Agric. Food Chem. 2002, 50, 6975-6980 6975 10.1021/jf020296n CCC: $22.00 © 2002 American Chemical Society Published on Web 10/19/2002