Oxygen Radical Scavenging Capacity Research Articles

Antioxidant and Pro-Oxidant Effects of Green Tea Extracts in Oxygen Radical Absorbance Capacity Assay

Green tea extracts (GTEs) [water (GTE-W) and 75% ethanol (GTE-E)] were investigated to characterize their propensities to act as antioxidants or as pro-oxidants by analyzing oxygen radical absorbance capacity (ORAC) and scavenging capacity for hydroxyl radical. When 2,2'-azobis(2-amidinopropane) dihydrochloride was used for the generation of peroxyl radicals, both GTE-W and GTE-E exhibited strong concentration-dependent scavenging activity through donating protons, which could be explained by their reducing property. When hydroxyl radicals were generated through the addition of Cu(2+) and H(2)O(2), GTE-W and GTE-E exhibited antioxidant activity or pro-oxidant activity, depending on their concentrations, which might be attributed to the metal chelating activity, the scavenging activity on hydroxyl radical, and/or the pro-oxidant activity to generate some reactive oxygen species. When Cu(2+) without H(2)O(2) was used as an oxidant in the assay, the copper-initiated pro-oxidant activities of GTE-W and GTE-W was consistent with the availability of (-)-epigallocatechin and (-)-epicatechin to generate hydrogen peroxide and/or hydroxyl radical. The pro-oxidant activity of GTE-W and GTE-E was demonstrated by the deoxyribose assay. These results indicate that both GTE-W and GTE-E can have pro-oxidant activity at lower concentrations and antioxidant activity at higher concentrations in the ORAC and deoxyribose assays using generated hydroxyl radicals.

Red Grapefruit Positively Influences Serum Triglyceride Level in Patients Suffering from Coronary Atherosclerosis: Studies in Vitro and in Humans

The contents of the bioactive compounds in red and blond grapefruits and their influence on humans suffering from hypertriglyceridemia were studied. It was found that red grapefruit has a higher content of bioactive compounds and a higher antioxidant potential than blond grapefruit, determined by oxygen radical scavenging capacity, 1,1-diphenyl-2-picrylhydrazyl, carotenoid bleaching, and Folin-Ciocalteu assays. Fifty-seven hyperlipidemic patients, ages 39-72 years, after coronary bypass surgery, recruited from the Institute's pool of volunteers, were randomly divided into three equal in number (19) groups: two experimental (red and blond groups) and one control group (CG). During 30 consecutive days of the investigation the diets of the patients of the red and blond dietary groups were daily supplemented with one equal in weight fresh red or blond grapefruit, respectively. Before and after this trial, serum lipid levels of all fractions and serum antioxidant activity were determined. It was found that serum lipid levels in patients of the red and blond groups versus the CG after treatment were decreased: (a) total cholesterol, 6.69 versus 7.92 mmol/L, 15.5%, and 7.32 versus 7.92 mmol/L, 7.6%, respectively; (b) low-density lipoprotein cholesterol, 5.01 versus 6.29 mmol/L, 20.3%, and 5.62 versus 6.29 mmol/L, 10.7%, respectively; (c) triglycerides, 1.69 versus 2.32 mmol/L, 17.2%, and 2.19 versus 2.32 mmol/L, 5.6%, respectively. No changes in the serum lipid levels in patients of the CG were found. In conclusion, fresh red grapefruit contains higher quantities of bioactive compounds and has significantly higher antioxidant potential than blond grapefruit. Diet supplemented with fresh red grapefruit positively influences serum lipid levels of all fractions, especially serum triglycerides and also serum antioxidant activity. The addition of fresh red grapefruit to generally accepted diets could be beneficial for hyperlipidemic, especially hypertriglyceridemic, patients suffering from coronary atherosclerosis.

Environmental prognostics: An integrated model supporting lysosomal stress responses as predictive biomarkers of animal health status

The potential prognostic use of lysosomal reactions to environmental pollutants is explored in relation to predicting animal health in marine mussels, based on diagnostic biomarker data. Cellular lysosomes are already known to accumulate many metals and organic xenobiotics and the lysosomal accumulation of the carcinogenic polycyclic aromatic hydrocarbon 3-methylcholanthrene (3-MC) is demonstrated here in the hepatopancreatic digestive cells and ovarian oocytes of the blue mussel. Lysosomal membrane integrity or stability appears to be a generic indicator of cellular well-being in eukaryotes; and in bivalve molluscs it is correlated with total oxygen and nitrogen radical scavenging capacity (TOSC), protein synthesis, scope for growth and larval viability; and inversely correlated with DNA damage (micronuclei), as well as lysosomal swelling (volume density), lipidosis and lipofuscinosis, which are all characteristic of failed or incomplete autophagy. Integration of multiple biomarker data is achieved using multivariate statistics and then mapped onto "health status space" by using lysosomal membrane stability as a measure of cellular well-being. This is viewed as a crucial step towards the derivation of explanatory frameworks for prediction of pollutant impact on animal health; and has facilitated the development of a conceptual mechanistic model linking lysosomal damage and autophagic dysfunction with injury to cells, tissues and the whole animal. This model has also complemented the creation and use of a cell-based bioenergetic computational model of molluscan hepatopancreatic cells that simulates lysosomal and cellular reactions to pollutants. More speculatively, the use of coupled empirical measurements of biomarker reactions and modelling is proposed as a practical approach to the development of an operational toolbox for predicting the health of the environment.

Letter to the editor

I read Önen et al’s article entitled “Effects of whole blood, crystalloid, and colloid resuscitation of hemorrhagic shock on renal damage in rats: an ultrastructural study” in the November 2003 issue (pp 1642–1649). The authors have shown that resuscitation of hemorrhagic shock with dextran 40 have beneficial effects on renal histology and relate this beneficial effect to reduced red cell slugging, volume expansion, and hemodilution-induced reduction in blood viscosity. However, intravital microscopic study of the intestinal mesenteric microcirculation has shown that resuscication of hemorrhagic shock with hypertonic saline solution containing dextran (HSD; 7.5% NaCl/6% dextran 70) restores microvascular blood flow better than resuscitation with an equal volume of Ringer’s lactate.1 Laser Doppler flowmetry has been used to show beneficial effects of HSD on restoration of intestinal and renal blood flows after resuscitation of hemorrhagic shock.2 Intravital microscopy has been used to show the prevention of hemorrhagic shock- induced leukocyte-endothelium adherence in liver sinusoids after resuscitation with HSD.3 Low-molecular-weight dextran has beneficial effects similar to those of high-molecular-weight dextran on microcirculation. Radioisotopic study of blood flow to multiple organs has shown that resuscitation of hemorrhagic shock with a pure solution of dextran 40 restores blood flow to these organs better than Ringer’s lactate.4 Additionally, dextran has been shown to have free oxygen radical scavenging capacity.5 Hemorrhagic shock has been shown to induce P-selection expression through free oxygen radical formation that leads to no-reflow phenomenon.6,7 Dextran 40 has been shown to prevent hemorrhagic shock-induced P-selectin expression thus abolish no-reflow phenomenon.8

Protection by free oxygen radical scavenging enzymes against glucose-induced embryonic malformations in vitro

This study addresses the possibility that the teratogenic effects of a diabetic pregnancy are associated with increased embryonic activities of free oxygen radicals. Rat embryos were cultured in 50 mmol/l glucose for 48 h and subsequently showed pronounced growth retardation and severe malformations. The enzyme inducer citiolone and the free oxygen radical scavenging enzymes superoxide dismutase, catalase and glutathione peroxidase protected against the disturbed growth and development of the embryos at 50 mmol/l glucose when added to the culture media. Enzymatic measurements indicated that citiolone induced an increased activity of superoxide dismutase in the embryonic tissues and that the added enzymes were taken up by both the yolk sac and the embryo proper. The protection against embryonic maldevelopment was thus conferred by agents that increased the free oxygen radical scavenging capacity of the embryonic tissues. The results suggest that a high glucose concentration in vitro causes embryonic dysmorphogenesis by generation of free oxygen radicals. An enhanced production of such radicals in embryonic tissues may be directly related to the increased risk of congenital malformations in diabetic pregnancy.