Long-term NO2 exposure of mice in the presence and absence of vitamin E. I. Effect on body weights and lipofuscin pigments

Thermodynamic and kinetic studies on antioxidant capacity of amentoflavone: a DFT (density functional theory) computational approach

Density functional theory (DFT) at the theoretical M06-2X/6-311G(d,p) level was used to assess thermodynamics and kinetics in the antioxidative action of amentoflavone (AF). The antioxidative HAT pathway (H-atom transfer) is assigned to this compound in gas, but the SPL-ET (sequential proton loss-electron transfer) is the main route in polar solvents methanol and water. In all four mediums gas, benzene, methanol, and water, 4‴-OH is the most active site in free radical quenching with the lowest BDE (bond dissociation enthalpy) values of 81.8-84.8 kcal/mol, as well as it exerted the PA (proton affinity) values of 29.8-33.0 kcal/mol in methanol and water. Regarding kinetics, when interacted with ^•OOH and ^•NO₂ in gas and methanol, 4‴-OH group is also responsible for the lowest ΔG^# values (Gibbs free energy of activation), and the highest rate constant K values. Acidic assessment also indicated that 4‴-OH is associated with the strongest acidity (the lowest pK_a). Two favorable oriented 4‴-OH and 7-OH groups further exhibited antioxidative activity since they prevented metal ions Zn²⁺ and Fe²⁺ from participating in free radical producing processes, in which the most stable complex [FeAF(H₂O)₄] generated the lowest IE value of -206.2 kcal/mol, and E_gap value of 3.491 kcal/mol, but the highest MIA values of 184.6 kcal/mol in methanol.

Kinetic Reaction Mechanism of Sinapic Acid Scavenging NO2 and OH Radicals: A Theoretical Study

The mechanism and kinetics underlying reactions between the naturally-occurring antioxidant sinapic acid (SA) and the very damaging ·NO2 and ·OH were investigated through the density functional theory (DFT). Two most possible reaction mechanisms were studied: hydrogen atom transfer (HAT) and radical adduct formation (RAF). Different reaction channels of neutral and anionic sinapic acid (SA-) scavenging radicals in both atmosphere and water medium were traced independently, and the thermodynamic and kinetic parameters were calculated. We find the most active site of SA/SA- scavenging ·NO2 and ·OH is the -OH group in benzene ring by HAT mechanism, while the RAF mechanism for SA/SA- scavenging ·NO2 seems thermodynamically unfavorable. In water phase, at 298 K, the total rate constants of SA eliminating ·NO2 and ·OH are 1.30×108 and 9.20×109 M-1 S-1 respectively, indicating that sinapic acid is an efficient scavenger for both ·NO2 and ·OH.

Mechanism of reaction of nitrogen dioxide radical with hydroxycinnamic acid derivatives: a pulse radiolysis study

Nitrogen dioxide radical (NO2.) is known as a toxic agent produced in the metabolism of nitrates and nitrites. By the use of the pulse radiolysis technique, the mechanism of the reaction of NO2. radical with hydroxycinnamic acid derivatives (HCA) was studied and the rate constants have been measured. The rate constants were found to be 7.4 x 10(8), 7.2 x 10(8), 8.6 x 10(8) dm3 mol(-1) s(-1) for ferulic acid, sinapic acid and caffeic acid, respectively. The reactions produce the corresponding phenoxyl radical.

Effect of dietary vitamin E upon fluorescent compounds of the rat uterus

Several water soluble and organic solvent soluble fluorescent peaks were observed in extracts of uteri from vitamin E deficient or supplemented rats following Sephadex column chromatography and spectrophotofluorometric analysis. Levels of one of the organic and two of the water soluble fluorescent peaks were found to be significantly higher in the uteri of vitamin E deficient rats than in vitamin E supplemented rats. Some of these fluorescent fractions may contribute to the brown discoloration that is known to occur in the uterus of vitamin E deficient animals.

Studies on the biochemical effects of nitrogen dioxide. IV. Relation between the change of lipid peroxidation and the antioxidative protective system in rat lungs upon life span exposure to low levels of NO2

This study examined the relation between lipid peroxidation and the antioxidative protective system in lungs of rats exposed to low levels of nitrogen dioxide (NO2). JCL:male Wistar rats were exposed to 0, 0.04, 0.4, and 4 ppm NO2 for 9, 18, and 27 months. Lipid peroxidation measured by TBA method, increased significantly in the 4 ppm NO2 group of the 9-month exposure and in the 0.4 and 4 ppm NO2 groups of the 18-month exposure. The activity of glutathione peroxidase measured with hydrogen peroxide as substrate decreased significantly in the 4 ppm NO2 group of the 9-month exposure and in the 0.4 and 4 ppm NO2 groups of the 18-month exposure. Furthermore, the activities of two glutathione S-transferases, aryl and aralkyl S-transferase, also decreased in the 0.4 and 4 ppm NO2 groups of the 18-month exposure, but not in any groups of the 9-month exposure. The activity of glutathione peroxidase measured with cumene hydroperoxide as substrate did not show any significant changes in any NO2 group. The activities of glucose-6-phosphate dehydrogenase and glutathione reductase were significantly higher than those in the control group for the 9-month exposure. In the 18-month exposure, however, they showed a tendency to return to control level. The activities of superoxide dismutase and disulfide reductase upon NO2 exposure for 9 and 18 months were not different from control values. To confirm that lipid peroxidation was increased with greater NO2 concentrations and exposure times, ethane and pentane exhalation in breath as an index of lipid peroxidation was examined. Ethane exhalation increased significantly following 0.04, 0.4, and 4 ppm NO2 exposure for 9 and 18 months. Furthermore, ethane formation of rats exposed to 0.04 and 0.4 ppm NO2 for 27 months also increased to twice the control level. On the other hand, after exposure to 4 ppm NO2 for 27 months, ethane levels returned to control level. Pentane formation increased significantly only in the 0.04 and 0.4 ppm groups in the 18-month exposure. Ethane exhalation in rats exposed to 0.04, 0.12, and 0.4 ppm NO2 for 9 and 18 months was similar. These results suggested that the antioxidative protective ability was decreased with prolonged exposure, while formation of cytotoxic lipid peroxides was increased.(ABSTRACT TRUNCATED AT 400 WORDS)

Toxicological data on NOx: an overview

This overview is based on experimental and epidemiological studies of NOx toxicity during the past decade. Approximately 130 published studies are cited and about one-fourth of these are discussed briefly under one of the following headings: acute and subacute studies, chronic low-level studies, human studies, and special studies. The latter section examines a selection of comparatively unique investigations, including several devoted to the pulmonary uptake and retention of NO2, and several examining the potential tumorigenicity of NO2. For each major section of the overview, a critical evaluation is attempted in terms of the impact of the appropriate studies on the extant NOx toxicological data base and on the current and planned air quality standards for NOx.

Long-term NO2 exposure of mice in the presence and absence of vitamin E. II. Effect of glutathione peroxidase

One hundred and twenty female mice fed diets containing various levels of vitamin E were continuously exposed to 0.5 ppm, 1.0 ppm nitrogen dioxide (NO2), and filtered air for 17 months. Blood, lung, and liver tissues were assayed for glutathione peroxidase (GSH-peroxidase) activity. Exposure to 0.5 ppm NO2 did not affect blood and lung GSH-peroxidase activity; 1.0 ppm NO2 exposure, however, caused suppression of the enzyme. A combination of vitamin E deficiency and 1.0 ppm NO2 exposure resulted in the lowest GSH-peroxidase activities in the blood and lung. High levels of vitamin E in the diet resulted in elevated GSH-peroxidase in the blood and lung. Liver GSH-peroxidase activity was unaffected by either dietary vitamin E or NO2 exposure. No inverse relationship was found between GSH-peroxidase levels and concentrations of organic solvent soluble lipofuscin pigments present in tissues.