|Vol. 6 (No. 1), pp. 1-57, 2016||doi: 10.5047/agbm.2016.00601.0001|
Division of Agricultural and Life Sciences, Graduate School of Environmental and Life Science, Okayama University, 1-1-1 Tsushima-naka, Kita-ku, Okayama 700-8530, Japan
(Received on March 3, 2014; Accepted on July 9, 2014; Online published on October 17, 2016)
Abstract: Polyphenols in foods possess potential to exhibit various beneficial effects in health promotion. Although polyphenols are well known to have antioxidant properties, a wealth of data suggests that most of the relevant mechanisms of disease prevention by polyphenols are not mainly related to their antioxidant properties. The protective function of phenolic compounds, which can be metabolically converted into electrophiles, might be ascribed to the induction of the cytoprotective responses against oxidative stress or toxic chemicals. Based on compelling evidence regarding the beneficial potential of polyphenols, various polyphenol-rich dietary supplements are being developed for public use. It is recently becoming apparent that commonly used dietary compounds can exert deleterious effects at pharmacological (supraphysiological) doses. Moreover, some human intervention trials showed not only failure to protect by polyphenols but accelerated development of chronic diseases in susceptible subjects. Thus, the present monograph tries to provide experimental evidence supporting the idea that optimal polyphenol supplementation can confer beneficial effects but high doses elicit adverse effects in an electrophilic reaction-dependent manner, thereby establishing a double-edge sword in health promotion. Current knowledge of polyphenols as phase II inducers is also discussed, with consideration of the metabolic activation, binding targets and factors influencing the biological activities of polyphenols. In addition, this monograph attempts to provide a brief perspective on the beneficial and harmful effects of food polyphenols.
Keywords: polyphenol, antioxidant, electrophile, phase II drug metabolizing enzyme, health promotion
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