The purpose of this study is to investigate the effects of bioflavonoids, epigallocatechin-3-gallate (EGCG) and quercetin, on the production of reactive oxygen and nitrogen species in the liver of rats under round-the-clock light exposure with an intensity of 1500 lux for 30 days while being kept on carbohydrate-lipid diet (20% fructose solution and appropriate food) for 60 days. In the liver tissues, the rate of the superoxide anion production by NADPH-dependent electron transport chains (microsomal monooxygenases and constitutive uncoupled NO synthases) increased by 1.93 times, by the mitochondrial respiratory chain by 1.89 times, and it was doubled by leukocyte NADPH-oxidase. The total activity of NO synthase was increased by 2.35 times, the activity of its inducible isoform increased by 2.57 times, and the concentration of alkali and alkaline earth metals peroxynitrites elevated by 1.68 times. Administration of bioflavonoids-epigallocatechin-3-gallate and quercetinsignificantly restrained the rate of superoxide anion production in the liver tissues by microsomal monooxygenases and NO synthase by 39.1 and 40.1%, by the mitochondrial respiratory chain by 37.2 and 34.4%, by leukocyte NADPH-oxidase by 35.0 and 32.1%, respectively. Epigallocatechin-3-gallate and quercetin inhibited the total activity of NO-synthase by 46.7 and 36.2%, the activity of its inducible isoform by 49.6 and 39,0%, increased the activity of the constitutive isoenzyme NO-synthase by 2.9 times and its coupling index by 4.5 and 4.7 times. Additionally, administration of these bioflavonoids lowered the concentration of peroxynitrites of alkali and alkaline earth metals by 30.5 and 34.3% compared to the respective values obtained in the group of rats, which did not receive the bioflavonoids, but were exposed to light and carbohydrate-lipid-rich diet. We suggest that epigallocatechin3-gallate and quercetin in the above experimental conditions are effective means to restrain the formation of reactive oxygen and nitrogen species in the liver tissue.

The aim of this study is to assess the effect of the polyphenol curcumin on lipid peroxidation (LPO) in the homogenate of the cerebral hemispheres from rats exposed to the round-the-clock lighting (RCL) and kept on high-calorie carbohydrate-lipid diet (HCCLD). The experiments were performed on 21 white male Wistar rats weighing 210-250 g, divided into 3 groups of 7 animals each. Animals of group 1 (control I) were kept on a standard vivarium diet and equal alternation of light and darkness periods. Rats of groups 2 and 3 during the period of RCL in the setting of HCCLD were daily injected 1 ml of 20% aqueous fructose solution intragastrically through a probe ("placebo", control II) and curcumin in a dose of 200 mg/kg, respectively. The level of lipid peroxidation in the cerebral homogenate was assessed by the formation of a colored trimethine complex in the reaction with thiobarbituric acid (TBA). Keeping rats on the RCL and HCCLD was accompanied by a significant increase in the concentration of TBA reactants before and after the incubation in pro-oxidant buffer solution, by 59.0 and 68.8%, respectively. The administration of curcumin under the experimental conditions significantly reduced the concentration of TBA-active products: before its incubation in the pro-oxidant buffer solution – by 24.4%, after the incubation – by 31.0% compared to the corresponding values in the 2nd group. This enables us to conclude that the administration of the polyphenol curcumin under exposing rats to RCL and keeping them on HCCLD significantly limits the LPO development in the cerebral homogenate of the cerebral hemispheres.