Effects Of Two Natural Antioxidants On Iron-Induced Hydroxyl Radical Production And Cytotoxity

Phytic acid and esculetin has been widely used as antioxidant. In this study, coumarin-3-caroxylic acid was used as fluorescent probe to detect hydroxyl radical; meanwhile, the effect of esculetin on 8HQ-Fe-induced cell viability was investigated in HepG2 cells. Esculetin was added to the cells 30 min before the addition of 8HQ-Fe.The results indicated that: Phytic acid could markedly enhance·OH produced by ferrous iron and hydrogen peroxide; similar enhancing effects were also observed for AMP and ATP;·OH formation could be enhanced by aminoacetic chelating agents such as ethyleneamine ethylenediaminetetraacetic acid (EDTA), diethylenetriamine-penta acetic acid (DTPA) and nitrilotriacetic acid (NTA);·OH produced by Fe/ H₂O₂/phytic acid were markedly inhibited by·OH scanvenging agents such as dimethyl sulfoxide(DMSO), ethanol (CH₃CH₂OH) and formate(HCOOH); similar enhancing effect by phytic acid was observed in the reaction of vanadyl and H₂O₂ (Fenton-like reaction). Esculetin exhibited a dose dependent protection against iron-induced cell toxicity; similar dose-dependent protection was also observed with two other esculetin derivatives such as 6,7-dihydroxy-4-methylcoumarin and 7,8-dihydroxy-6-methoxycoumarin; in the absence of non-toxic esculetin but in the presence of concentrations of 8-hydroxyquinoline-Fe(II) complex (100μM 8-hydroxyquinoline, 100μM ferrous), cell toxicity was observed.The results are quite related to the mechanism of iron chelation, which help us know more about the property of these two antioxidants...