A new evaluation method for anti-oxidant activity based on structure change of protein caused by radicals

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A simple method to evaluate antioxidant activities of water-soluble ingredients of foods has been developed in this research project. Protective effects of antioxidants against hypochlorite ion or hydroxyl radical have been studied by comparing changes in absorbance of myoglobin (a standard reference) at 409 nm. Protective ratio, defined by absorbance changes of myoglobin with or without the antioxidant, was a good indicator to quantitatively evaluate the antioxidant activity against the hypochlorite radical or the hydroxyl radical, respectively. Radar charts indicating the antioxidant activities against DPPH (1, 1-cliphenyl-2-picrylhydradyl), hypochlorite ion, and hydroxyl radical clearly differentiated the characteristics of five antioxidants including carnosine, glutathione, and vitamin C.In order to demonstrate the effectiveness of the proposed method, antioxidant activities of three polyphenol compounds, teas (green tea, oolong tea, and black tea), and five commercially available bottled teas have been evaluated. Teas were chosen as examples because comprehensive methods to evaluate antioxidant properties have not been established yet in spite of consumers' strong concern fir the antioxidant activities of teas. All polyphenol compounds showed relatively high activities against all three radicals. All teas showed similar patterns as the polyphenol compounds in the radar charts. The strength of the activities, however, strongly depends on the samples. Thus, the antioxidant activities of various teas have been successfully evaluated in a comprehensive way using the radar charts. The simple method proposed in this rematch project would be useful to evaluate and characterize the activities of water-soluble antioxidants contained in various food materials.