Alkylperoxyl radical-scavenging activity of various flavonoids and other phenolic compounds: implications for the anti-tumor-promoter effect of vegetables.
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.
Sawa
T
T
Department of Microbiology, Kumamoto University School of Medicine, Japan.
Nakao
M
M
Akaike
T
T
Ono
K
K
Maeda
H
H
D016588:Anticarcinogenic Agents / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy; D007887:Fabaceae / Q000737:chemistry; D005419:Flavonoids / Q000737:chemistry*; D016166:Free Radical Scavengers / Q000737:chemistry*; D010636:Phenols / Q000737:chemistry*; D010946:Plants, Medicinal; D014675:Vegetables / Q000737:chemistry*
D016588:Anticarcinogenic Agents; D005419:Flavonoids; D016166:Free Radical Scavengers; D010636:Phenols