2600 JOURNAL OF FOOD SCIENCE—Vol. 67, Nr. 7, 2002 © 2002 Institute of Food Technologists Food Chemistry and Toxicology Antioxidant Properties of Cereal Products L. YU, J. PERRET, B. DAVY, J. WILSON, AND C.L. MELBY ABSTRACT: Four commercial cereal products were examined and compared for their free radical scavenging prop- erties, chelating capacity, and total phenolic contents. The Quaker Oat Bran™ ready-to-eat cold cereal showed the greatest activity to quench DPPH radicals, while the Quaker oatmeal had the highest capacity against ABTS · + . Significant Fe 2 + chelating activity was also detected in these cereal products with EDTA equivalents of 0.08 to 0.48 mg/g cereals. The total phenolic contents were 203 to 524 mg per gram of cereal products. These results indicate that readily available cereal products contain significant levels of antioxidants and may be an important source of dietary antioxidants. Keywords: cereal products, antioxidants, radical scavenging, chelating capacity, phenolic contents Introduction R EACTIVE OXYGEN SPECIES (ROS) OR FREE RADICALS ARE GENERAT ed as byproducts or intermediates during normal metabo- lism. ROS is a collective term used to include both the oxygen radicals (hydroxyl radical) and some nonradical reactive deriva- tives of oxygen (hydrogen peroxide) (Halliwell and Gutteridge 1999). A balance between formation and removal of these ROS or radicals is required to maintain normal physiological functions for human health. Elevated levels of ROS and free radicals occur when formation of ROS or free radicals is favored. The elevated cellular levels of ROS or free radicals cause damage to nucleic ac- ids, proteins, and membrane lipids and have been associated with many aging-related health problems including carcinogen- esis and heart diseases (Halliwell and others 1992; Halliwell 1996; Wang and Jiao 2000). Dietary antioxidant treatments may terminate free radical attacks to reduce the risks of these diseas- es or to promote general human health (Neff 1997; Chung and others 1999; Baublis and others 2000a). Significant levels of antioxidants have been detected in grains and grain-based cereal products (Collins 1989; Emmons and others 1999; Auerbach and Gray 1999; Handelman and oth- ers 1999; Baublis and others 2000ab). In fact, oat flour, because of its antioxidant properties, was used as a source of antioxidants (preservation) before the days of BHT and BHA (early 1900s). It has been suggested that these antioxidants may contribute to the health benefits of grain-based foods in reducing the inci- dence of aging-related chronic diseases including heart diseases and some cancers (Miller and others 2000). The antioxidants may act as free radical scavengers, reducing agents, chelating agents for transition metals, quenchers of singlet oxygen molecules, and activators of antioxidative defense enzyme systems, to suppress radical damage in biological systems (Zielinski and Kozlowska 2000). Earlier, Onyeneho and Hettiarachchy (1992) reported that freeze-dried extracts from durum wheat (Triticum durum) inhib- ited soy oil peroxidation. Wheat extracts (Triticum aestivum L.) were also reported to inhibit radical cation ABTS · + and prevent L- a-phosphatidylcholine liposome oxidation (Zielinski and Ko- zlowska 2000). In addition to wheat, oat extracts (Avena sativa L.) showed antioxidant capacity against low-density lipoprotein (LDL) oxidation and R-phycoerythrin protein oxidation in the ox- ygen radical absorbance capacity assay (Handelman and others 1999), and prevented -carotene oxidation (Emmons and others 1999). These data suggested that both wheat- and oat-based food products may be important sources of dietary antioxidants (Emmons and others 1999; Baublis and others 2000b). Further- more, the antioxidant potential and bioavailability of cereal anti- oxidants may depend on the species and varieties of grains, frac- tions of the grain (bran, flour, or whole grain), and processing conditions (Zielinski and Kozlowska 2000). Recently, aqueous ex- tracts from wheat-based ready-to-eat breakfast cereals were shown to inhibit iron- or ascorbic acid-induced phosphatidylcho- line liposome oxidation (Baublis and others 2000a). The objective of this study was to determine and compare the 4 commercial cereal products for their free radical scavenging ca- pacity against 2,2-diphenyl-1-picryhydrazyl radical (DPPH·), their radical cation ABTS · + scavenging activity, their chelating ca- pacity against Fe 2 + , and for their total phenolic contents. We rec- ognize that antioxidant concentrations and activity may be al- tered by the manner in which these commercial products are prepared. Nevertheless, we chose these products because of their widespread availability and use in the United States. Studying such commercially prepared products may provide useful information to consumers and also incentive to food man- ufacturers to promote the consumption and production of value- added foods for improving human health. Materials and Methods Materials The cereal samples used in this study included Oatmeal (Quaker Oats™, Barrington, Ill., U.S.A.), Quaker Oat Bran™ ready-to-eat cold cereal and Mother’s Whole Wheat Hot Natural Cereal™ (both from Quaker Oats™), and Frosted Mini- Wheats™ (Kellogg Co., Battle Creek, Mich., U.S.A.). 2,2-diphe- nyl-1-picryhydrazyl radical (DPPH·), ethylenediaminetetraace- tate (EDTA), -tocopherol, L-ascorbic acid, butylated hydroxytoluene (BHT) and 2,2’-bipyridyl were purchased from Sigma-Aldrich (St. Louis, Mo., U.S.A.). A total antioxidant status kit was purchased from Randox Laboratories Ltd. (San Francisco, Calif., U.S.A.). All other chemicals and solvents were the highest commercial grade and used without further purification. Extraction and sample preparation Ten grams of each cereal product was ground and extracted for 3 h with ethanol under nitrogen, using a Soxhlet extractor (Yu and others 2002). The ethanol extracts were concentrated to a fi- JFS: Food Chemistry and Toxicology