ObjectiveThe aim of this study was to evaluate the protective effects of quercetin, rutin, hesperidin and myricetin against reactive oxygen species production with the oxidizing action of tert-butylhydroperoxide in erythrocytes from normal subjects and sickle cell anemia carriers treated with hydroxyurea. MethodsDetection of intracellular reactive oxygen species was carried out using a liposoluble probe, 2',7'-dichlorfluorescein-diacetate (DCFH-DA). A 10% erythrocyte suspension was incubated with flavonoids (quercetin, rutin, hesperidin or myricetin; 30, 50, and 100 µmol/L), and then incubated with tert-butylhydroperoxide (75 µmol/L). Untreated samples were used as controls. ResultsRed blood cell exposure to tert-butylhydroperoxide resulted in significant increases in the generation of intracellular reactive oxygen species compared to basal levels. Reactive oxygen species production was significantly inhibited when red blood cells were pre-incubated with flavonoids, both in normal individuals and in patients with sickle cell anemia. Quercetin and rutin had the highest antioxidant activity, followed by myricetin and hesperidin. CONCLUSION:Flavonoids, in particular quercetin and rutin, showed better antioxidant effects against damage caused by excess reactive oxygen species characteristic of sickle cell anemia. Results obtained with patients under treatment with hydroxyurea suggest an additional protective effect when associated with the use of flavonoids.

Oxidative stress parameters in children's erythrocytes were determined using simple laboratory methods with small volumes of blood; these biomarkers can be useful to evaluate disease progression and outcomes in patients.

Sickle cell disease promotes hemolytic anemia and occlusion of small blood vessels due to the presence of high concentrations of hemoglobin S, resulting in increased production of reactive oxygen species and decreased antioxidant defense capacity. The aim of this study was to evaluate the protective action of a standardized extract of Ginkgo biloba (EGb 761), selected due to its high content of flavonoids and terpenoids, in erythrocytes of patients with sickle cell anemia (HbSS, SS erythrocytes) subjected to oxidative stress using tert-butylhydroperoxide or 2,2-azobis-(amidinepropane)-dihydrochloride, in vitro. Hemolysis indexes, reduced glutathione, methemoglobin concentrations, lipid peroxidation, and intracellular reactive oxygen species were determined. SS erythrocytes displayed increased rates of oxidation of hemoglobin and membrane lipid peroxidation compared to normal erythrocytes (HbAA, AA erythrocytes), and the concentration of EGb 761 necessary to achieve the same antioxidant effect in SS erythrocytes was at least two times higher than in normal ones, inhibiting the formation of intracellular reactive oxygen species (IC50 of 13.6 µg/mL), partially preventing lipid peroxidation (IC50 of 242.5 µg/mL) and preventing hemolysis (IC50 of 10.5 µg/mL). Thus, EGb 761 has a beneficial effect on the oxidative status of SS erythrocytes. Moreover, EGb 761 failed to prevent oxidation of hemoglobin and reduced glutathione at the concentrations examined.

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Because oxidative damage to erythrocytes plays an important pathophysiologic role in many diseases and there are some difficulties in obtaining reference intervals for children in many laboratory tests, this work intends to describe the determination of oxidative stress parameters and the results obtained for children. A total of 280 blood samples were obtained from children between 8 and 11 years old, without any hematological disease. Samples were analyzed for seven oxidative stress parameters, methemoglobin, reduced glutathione, TBARS, percentage of hemolysis and activity of the enzymes G6PD, superoxide dismutase, and catalase. To draw a comparison, the same parameters were analyzed in children with sickle cell disease. Because all results presented normal distribution in the Kolmogorov-Smirnov, data were expressed as 2.5 and 97.5th accumulated percentiles and the statistical analysis between male and female children was performed using Student t-test. A p value <0.05 was considered significant. Except for hemolysis, no significant difference was observed on oxidative stress parameters, in normal children, separated by sex. Except for reduced glutathione and superoxide dismutase, significant differences were observed in all parameters between normal children and those with sickle cell disease. Oxidative stress parameters can be determined in children using simple laboratory methods with small volumes of blood and the establishment of reference intervals is necessary to improve clinical decisions.