Relationship between effects of phenolic compounds on the generation of free radicals from lactoperoxidase-catalyzed oxidation of NAD(P)H or GSH and their DPPH scavenging ability.
The influence of various phenolic compounds on the lactoperoxidase (LPO)/hydrogen peroxide (H2O2)-catalyzed oxidation of biochemical reductants such as reduced beta-nicotinamide adenine dinucleotide (NADH), reduced beta-nicotinamide adenine dinucleotide phosphate (NADPH) or reduced glutathione (GSH) was investigated by electron spin resonance (ESR) spectroscopy. Micromolar quantities of phenolic compounds such as 17beta-estradiol, phenol, and p-chlorophenol enhanced the LPO/H2O2-catalyzed oxidation of NAD(P)H or GSH to generate a large amount of superoxide radical (O2*-) or glutathione thiyl radical (GS*), while, phenolic compounds such as quercetin and Trolox C greatly suppressed the generation of O2*- and GS*. In order to elucidate the effects of phenolic compounds on the generation of O2*- and GS*, their quenching activities for a stable radical, 1,1-diphenyl-2-picrylhydrazyl (DPPH), were investigated by ESR spectroscopy. 17beta-Estradiol, phenol, and p-chlorophenol showed very weak scavenging activities for DPPH, but quercetin and Trolox C showed strong activities. This suggests that the ability of phenolic compounds to enhance LPO/H2O2-catalyzed oxidation of NAD(P)H or GSH relates inversely to their ability to quench DPPH. That is, phenolic compounds having weak quenching activity against DPPH may enhance the LPO/H2O2-catalyzed oxidation of NAD(P)H or GSH to generate a large amount of O2*- or GS*.
National Institute of Radiological Sciences, Chiba, Japan. ueda@nirs.go.jp
J
J
Ueda
Y
Y
Tsuchiya
T
T
Ozawa
D015764:Bepridil / Q000031:analogs & derivatives* / Q000737:chemistry*; D001713:Biphenyl Compounds; D002384:Catalysis; D004578:Electron Spin Resonance Spectroscopy; D016166:Free Radical Scavengers / Q000737:chemistry*; D005609:Free Radicals / Q000737:chemistry; D005978:Glutathione / Q000737:chemistry*; D007784:Lactoperoxidase / Q000737:chemistry*; D009249:NADP / Q000737:chemistry*; D010084:Oxidation-Reduction; D010636:Phenols / Q000737:chemistry*; D010851:Picrates
D001713:Biphenyl Compounds; D016166:Free Radical Scavengers; D005609:Free Radicals; D010636:Phenols; D010851:Picrates; D009249:NADP; D015764:Bepridil; C004931:1,1-diphenyl-2-picrylhydrazyl; D007784:Lactoperoxidase; D005978:Glutathione