Genotype and Environmental Variation in Phenolic Content, Phenolic Acid Composition, and Antioxidant Activity of Hard Spring Wheat ARCHIE MPOFU,HARRY D. SAPIRSTEIN, AND TRUST BETA* Department of Food Science, University of Manitoba, Winnipeg, Manitoba, R3T 2N2 Canada The health-promoting effects of whole-grain wheat likely derive from phenolic compounds and other antioxidants that also make wheat a potential source of functional food ingredients. The objective of this study was to determine the effects of genotype and growing environment on the phenolic contents and antioxidant activities of alcohol-soluble extracts from commercial wheat cultivars. Total phenolic contents (TPCs), antioxidant activities (AOAs), and concentrations of six phenolic acids were measured in six red- and white-grained hard spring wheat genotypes grown at four diverse locations in Western Canada during the 2003 crop year. There were significant differences among genotypes and environments for TPC, AOA, and concentrations of all the phenolic acids measured. The predominant indicators of antioxidant potential, i.e., TPC, AOA, and ferulic acid (FA) concentration were highly intercorrelated (r > 0.72). For these indices, the Canada Western (CW) Red Spring wheat cultivars Neepawa and AC Elsa had the highest levels, whereas an analogous CW hard white spring wheat cultivar, AC Snowbird, had the lowest levels. Grain color did not appear to be a factor in the expression of antioxidant-related parameters. For both TPC and AOA, as well as for vanillic acid, syringic acid, and ferulic acid, environmental effects were considerably larger than genotype effects. Neither growing temperature nor rainfall from anthesis to maturity appeared to be related to the environmental variation that was observed. Genotype × environment interaction was small for all parameters compared with genotype and location effects and was significant only for TPC. Genotype variation for antioxidant properties indicates that it would be possible to select for these quantitative traits in a breeding program. However, the significant environmental variation observed would delay and/or complicate this process. KEYWORDS: Wheat; genotype by growing location; antioxidant activity; total phenolic content; DPPH INTRODUCTION Regular consumption of whole-grain foods has been found to be associated with reduced total mortality (1, 2), as well as reduced risk of coronary heart disease (CHD) (3), ischemic stroke (4), and type 2 diabetes (5, 6). Health-beneficial properties of whole-wheat grains can be largely ascribed to the presence of phytochemicals in the diet that reduce oxidative stress, thereby reducing the risk of chronic diseases. Wheat is a critically important commodity worldwide. It is grown on more land area than any other commercial crop and is the most important food grain source for humans. Quantification of health-beneficial phytochemicals present in whole grain and its products is important for the breeding and marketing of wheat based on its potential to promote health in line with increasing consumer demands for healthier foods. Wheat has significant levels of antioxidants (7-14). Among the different antioxidants present in wheat, phenolic compounds seem to have the greatest potential of being beneficial to health (15). Phenolic compounds inhibit lipid peroxidation by scaveng- ing free radicals such as hydroxyl radicals (HO•) and peroxyl radicals (ROO•) resulting in the formation of low energy phenolic radicals whose energy is not sufficient to promote lipid oxidation at biologically significant rates (16). Wheat phenolic compounds exist in free, bound and soluble conjugated forms (7). Ferulic, p-coumaric, and vanillic acids are the most dominant free phenolics and are found together with other phenolics including caffeic, chlorogenic, gentisic, syringic, and p-hydroxybenzoic acids (7). The wheat genotype (G), the environment (E) in which wheat is grown, and possibly genotype-environment (G × E) interac- tions can likely strongly influence the levels of grain antioxi- dants. The literature is, however, relatively deficient on this topic. Three hard winter wheat varieties (Akron, Trego, and Platte) grown in a single field location differed significantly in their capacities to quench free radicals using scavengers such as 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azino-di-(3- ethylbenzthiazoline-6-sulfonate) (ABTS) radicals (9). Growing location had a strong influence on the antioxidant activity of * To whom correspondence should be addressed. Address: Department of Food Science, University of Manitoba, Winnipeg, Manitoba, Canada R3T 2N2. Phone: (204) 474-8214. Fax: (204) 474-7630. E-mail: Trust_Beta@ UManitoba.CA. J. Agric. Food Chem. 2006, 54, 1265-1270 1265 10.1021/jf052683d CCC: $33.50 © 2006 American Chemical Society Published on Web 01/31/2006