Chapter 1
Antioxidant Measurement and Applications: An Overview 1
Downloaded by UNIV OF GUELPH LIBRARY on August 6, 2012 | http://pubs.acs.org Publication Date: March 12, 2007 | doi: 10.1021/bk-2007-0956.ch001
Fereidoon Shahidi and Chi-Tang Ho
2
1
Department of Biochemistry, Memorial University of Newfoundland, St. John's, Newfoundland A1Β 3X9, Canada Department of Food Science, Rutgers, The State University of New Jersey, 65 Dudley Road, New Brunswick, NJ 08901
2
Antioxidants are added to fats, oils and fatty foods to prevent their oxidative deterioration. Antioxidants also protect the integrity of cellular structures and macromolecules from damage due to free radicals. Carotenoids and phenolic compounds are major dietary antioxidants. Because of the importance of antioxidant potential in foods and dietary supplements, it is necessary to have good and reliable methods for measuring antioxidant activity. Various in vitro and in vivo methods for assessing antioxidant activities are discussed.
Introduction Autoxidation occurs widely in fats, oils and lipid-containing foods, and causes food quality deterioration with concomitant generation of loss of nutrients, unpleasant flavors, and even potentially toxic substances. Among the methods for preventing oxidation, addition of antioxidants is the most effective, convenient and economical one (7). Antioxidants are also important to human health. Antioxidant protection from damage due to free radicals is vital for the integrity of cellular structures
2
© 2007 American Chemical Society
In Antioxidant Measurement and Applications; Shahidi, F., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2007.
Downloaded by UNIV OF GUELPH LIBRARY on August 6, 2012 | http://pubs.acs.org Publication Date: March 12, 2007 | doi: 10.1021/bk-2007-0956.ch001
3 and macromolecules (2,3). As we age, the system which utilizes antioxidants for our defense and protection also declines, and can be aggravated by the presence of various oxidative stresses caused by pollution, exercise, smoke exposure and radiation. This defense system operates through a series complex networks between vitamins C and E, carotenoids, zinc, copper, selenium, and magnesiumdependent enzyme antioxidants as well as other phytonutrients, which together perform highly involved recycling and regeneration reactions to optimize free radical protection. Deficiencies in any of the mentioned necessary components could potentially lead to a severely compromised defense system (4,5). Owing to the incomplete efficiency of our endogeneous defense systems, dietary antioxidants are needed to overcome the oxidative damage (5).
Dietary Antioxidants Carotenoids and phenolic compounds are major dietary antioxidants. Both of these groups of compounds contain hundred of members (6). Carotenoids are natural, fat-soluble pigments that provide bright coloration to plants and animals and act as antioxidants, which include the possibility of providing vitamin A activity. One defining characteristic of carotenoids is the chemical structure of what is often considered their backbone molecule, a 40carbon polyene chain. The polyene backbone consists of a pattern of conjugated double bonds, which allows the carotenoids to take up excess energy from other molecules (7). This characteristic may be responsible for the antioxidant activity seen in biological carotenoids. In addition to scavenging free radicals, other health benefits related to this observed antioxidative activity include protection from sunburn and inhibition of the development of certain types of cancers (
