SUMMARY A simple spectrophotometric method of determination of peroxyl radicaltrapping capacity (PRTC) of body fluids and food products is proposed. In this method, decomposition of 2,2'-azobis(2-amidopropane) hydrochloride (ABAP) is the source of peroxyl and alkoxyl radicals which oxidize 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) to a green cation radical. Antioxidant present in a sample inhibit the reaction; the induction time of the reaction is proposed as a parameter enabling determination of antioxidant content. Standard assay conditions are: 20 mM ABAP and 150 IJM ABTS in 0.1 M phosphate buffer, pH 7.0, at 37~ absorbance is monitored at 414 nm. A 10-min assay allows for determination of the induction time of appropriately diluted sample. As examples of application of this method, PRTC values of several types of beverages are reported.
The hyperthermic exposure (39-49 degrees C) of human erythrocyte membranes augmented their lipid peroxidation stimulated by 0.1 mM FeCl3 + 1.5 mM ascorbate while having no significant influence on the non-stimulated lipid peroxidation. No effect of hyperthermia and lipid peroxidation on the post-exposure fluidity of the erythrocyte membrane lipids was found by the fluorescence anisotropy of hexatriene and trimethylaminophenylhexatriene, and excimerization efficiency of pyrene. Exposure to iron/ascorbate increased the accessibility of membrane protein tryptophan residues to acrylamide as judged by fluorescence quenching. These results suggest a higher sensitivity of membrane protein organization than of membrane lipid fluidity to the effect of the system inducing lipid peroxidation.
SummaryLuminal chemiluminescence induced in the presence of yeast cells and yeast cell homogenates was significantly induced by exogenous oxidants (hydrogen peroxide and menadione), ted-Butyl hydroperoxide did not stimulate chemiluminescence by itself but augmented menadione-induced chemiluminescence. Comparison of yeast strains deficient in catalase, superoxide dismutase or glutathione showed that only glutathione-deficient strains showed elevated chemiluminescence in this system. These results support the idea that more reactive species than hydrogen peroxide and superoxide are critical in the induction of luminal chemiluminescence.
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