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Alkylperoxyl
radical-scavenging activity of various flavonoids and other phenolic compounds:
implications for the anti-tumor-promoter effect of vegetables.
J Agric Food Chem 1999 Feb;47(2):397-402
Sawa T, Nakao M, Akaike T, Ono K, Maeda H.
Department of Microbiology, Kumamoto University School of Medicine, Japan.
We recently reported that alkylperoxyl radical (ROO(*)) enhanced carcinogenesis
in rats treated with carcinogen (Sawa et al. Cancer Epidemiol. Biomarkers Prev.
1998, 7, 1007-1012), and the tumor promoting action of ROO(*) could be reduced
by addition of hot-water extracts of vegetables (Maeda et al. Jpn. J. Cancer
Res. 1992, 83, 923-928). Here we described the ROO(*)-scavenging activity of
flavonoids and nonflavonoid phenolics and their role in anti-tumor-promoter
effects. A model molecular species, ROO(*), was generated from tert-butyl
hydroperoxide (t-BuOOH) and heme iron, and the scavenging of t-BuOO(*) was
determined by (a) bioassay based on the bactericidal action of ROO(*), (b)
luminol-enhanced chemiluminescence, and (c) electron spin resonance. Of 17
authentic plant phenolics tested, 9 compounds (including rutin, chlorogenic
acid, vanillin, vanillic acid, neohesperidin, gallic acid, shikimic acid,
rhamnetin, and kaempferol) showed remarkably high ROO(*)-scavenging activity.
Some of them were detected and quantified in hot-water extracts of mung bean
sprouts, used as the model vegetable, and their contents increased after
germination, which paralleled very well to the ROO(*)-scavenging capacity of the
vegetable extracts. Thus, a diet rich in these radical scavengers would reduce
the cancer-promoting action of ROO(*). Consequently, the carcinogenic potentials
of oxygen-related radicals may be suppressed.
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