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标题：Antioxidant Activity of Caffeic Acid through a Novel Mechanism under UVA Irradiation
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作者：Hiroko Mori ; Hideo Iwahashi
期刊名称：Journal of Clinical Biochemistry and Nutrition
印刷版ISSN：0912-0009
电子版ISSN：1880-5086
出版年度：2009
卷号：45
期号：1
页码：49-55
DOI：10.3164/jcbn.08-258
出版社：The Society for Free Radical Research Japan
摘要：Effect of caffeic acid on the formation of hydroxyl radicals was examined during xanthone-mediated photosensitization. The reaction was performed on irradiation (λ = 365 nm) of the standard reaction mixture containing 15 μM xanthone, 0.1 M 5,5-dimethyl-1-pyrroline N -oxide (DMPO) and 20 mM phosphate buffer (pH 7.4) using electron paramagnetic resonance (EPR) with spin trapping. Caffeic acid inhibited the formation of hydroxyl radicals. Caffeic acid hardly scavenged both hydroxyl radicals and superoxide radicals under conditions employed in this paper in spite of its ability to act as a hydrogen donor or a reagent for the aromatic hydroxylation, because high concentration of DMPO trapped hydroxyl radicals overwhelmingly. Furthermore, caffeic acid inhibited the formation of hydroxyl radicals in the standard reaction mixture with EDTA under UVA irradiation. Accordingly, the inhibitory effect of caffeic acid on the formation of hydroxyl radicals in the standard reaction mixture under UVA irradiation is not due to its ability to chelate iron. Thus, the inhibitory effect of caffeic acid seems to occur in the standard reaction mixture under UVA irradiation through a novel antioxidation activity, i.e. , ability to quench the exited xanthone.
关键词：radicals;xanthone;quenching;UVA;caffeic acid