Papers by Keyword: Free Radical

Abstract: Synthesis of nanoparticles of transition metals by using medicinal plants has been outstreched in recent years because of the characteristic features which are embodied in the end product. This work is proceded with the aim to synthesize and optimize copper nanoparticles (CuNPs-Pl) using aqueous extract of Polyalthia longifolia leaves (PlL) for characterization and evaluation of antimicrobial and antioxidant potential. The synthesis of CuNPs-Pl was confirmed by visual inspection of the dark brown residues in the reaction flask and via absorption band around 580nm by UV/Visible spectroscopy. Synthesis process was optimized through investigation of environmental variables. FTIR analysis was carried out for both PIL and CuNPs-Pl which identified the presence of alkanes, alcoholic, and aldehydic groups in the PlL and their encapsulation on the copper surface. The synthesized CuNPs-Pl were found to be spherical and rod shaped, and polydispersed when investigated through SEM study. Similarly, these nanoparticles had monoclinic structure and crystalline nature when analyzed by XRD. Moreover, these nanoparticles showed metallic form when EDX examination was done. Further, biological activities were performed. The synthesized nanoparticles showed considerable inhibition zones against Escherichia coli (12mm), Bacillus subtilis (11mm), Aspergillus niger (10mm), and Schyzophyllum commune (16mm) which depicted their powerful antibacterial and antifungal activity. Likewise, CuNPs-Pl were effeciently able to quench free radicals as indicated from the 2, 2-diphenyl-1-picrylhydrazyl (DPPH), hydrogen peroxide (H₂O₂), and nitric oxide (NO) assays by exhibiting 86.32, 50.45, and 48.23% inhibition respectively. Thus, the contemporary work has substantiated that low cost CuNPs-Pl can be highly proficient alternate or substitute of synthetic formulations.

Abstract: Electron paramagnetic resonance (EPR) spectrometer was widely applied to physics, chemistry and biomedicine. This research provided possible electron and valence information of environmental samples interaction through high sensitivity. The EPR signals of transition metals and organic radicals were distinguished well. Three kinds of carbon nanotubes (CNTs) (MW50, MW30 and MWG) had strong EPR signals. Addition of transition metals may be a suitable way to decrease environmentally persistent free radicals (EPFRs). The potential risks of EPFRs in BC and the reactive free electron in transition metals must be addressed to ensure their safe and scientific absorption application.

Abstract: In order to achieve lactic acid bacteria (LAB) with high antioxidant activity and provide a theoretical reference for the development of natural antioxidants, 8 stains of LAB were studied by hydroxyl radical scavenging experiments, DPPH and hydroxyl radical assays, anti-lipid peroxidation assays and reducing powder evaluation experiments. The results showed that the antioxidant capabilities of the 8 strains of LAB were quite different and the fermentation supernatant had better antioxidant activity than the intact cell and the intracellular extracts. Moreover, Lb,Lr and Lm₁ strains demonstrated better capacity on antioxidant activity than others, which could be considered as potential antioxidant strains to be applied in functional foods.

Abstract: Deinococcus radiodurans strain R1 synthesizes deinoxanthin, a unique carotenoid product, which contributes to cell resistance following various stresses. The biosynthetic pathway of deinoxanthin is unclear, although several enzymes are presumed to be involved. The lack of CrtD decreased the antioxidant capacity of the mutant deficient in dr2250 compared with the wild-type, indicating that the C-3',4'-desaturation step contributes to the antioxidant capacity of deinoxanthin in D. radiodurans.

Abstract: Carotenoids demonstrated multiple antioxidant activities, including the ability to scavenge single oxygen and reactive oxygen radicals. Superoxide anion/radials, produced by exogenous chemical or physical stimuli and endogenous metabolic processes, can be another source of harmful reactive oxygen species (ROS) in vivo. The main components of carotenoids, lycopene, from Blakeslea trispora were separated by HPLC. In the current study, we reported the direct scavenging of superoxide anion by the carotenoids from Blakeslea trispora evaluated by electron paramagnetic resonance (EPR) spectroscopy, employing the spin-trap DMPO.

Abstract: Experimental study the degradation efficiency of toluene by bipolar corona discharge coupled with TiO₂ photocatalysis. Bipolar corona discharge can degrade the toluene efficiently and rapidly, the final products are mainly carbon dioxide and water. Toluene removal efficiency reduces when the initial concentration of toluene increasing, while toluene removal quantity is increased. Removal of toluene decreases with the gas flow rate increasing, the removal quantity first increases and then decreases. Bipolar corona discharge and a photocatalytic coupling can inprove the degradation efficiency further. Increase of the applied voltage help to improve the removal of toluene, and also to improve the coupling effect of the photocatalyst. In optimized conditions, the removal efficiency of toluene can be more than 90%. The chemical reaction process of the toluene oxidation and the TiO₂ catalysis mechanism are discussed. It is pointed out that the OH* produced by corona discharge has important significance for rapid oxidation of toluene.

Abstract: The compounds, which extracted from Equisetum arvense, Crataegus pinnatifida Bunge, Rosa maximowicziana Regel and Physalis alkekengi, were selected to determine the content of flavonoids and polysaccharides by a visible light spectrophotometry, and the antioxidant activity was determined by a chemical method. The results showed that the content of flavonoids in our compounds was 0.204 mg/g and the polysaccharides was 2.498 mg/g. In scavenging experiments, the levels of hydroxyl radicals and superoxide anion were lower compared with negative control, but the levels were still higher than positive control. The ability to scavenge superoxide anion was more powerful than hydroxyl radicals. This determined that our compound preparation extract have the ability to scavenge hydroxyl radicals and superoxide anion.

Abstract: The mechanism of CH₄-CO₂ free radical reforming was investigated by DFT and B3LYP methods. The gained results have indicated that the main dehydrogenation of CHx were lost hydroxide atom step by step.The form process of carboxyl was very easy. The decomposition of the carboxyl or the compound included carboxyl were direct decomposition into carbon monoxide at low temperature. The intermediate as ·COOH and CH₃COO·were also easy to take place the decomposited into carbon monoxide or CH₃O.The hydroxide radical also could combine CH₃·,CH₂·,CH· into sterols. The decomposition of CH_xO(x≠3) is easy and through direct dehydrogenation. The decomposition of methanol were three channels and it can creat H₂, C₂H₆, H₂O.

Abstract: The SENKIN subroutine package of CHEMKIN chemical kinetics package was used to analyze the gas explosion at three initial temperatures of 1000K, 1050K and 1100K in restricted space, based on the detailed chemical kinetics mechanism of methane combustion. The changes of explosion temperature, explosion pressure and free radicals O, H and OH generated were discussed. The results show that with elevated initial temperature, the explosion temperature increases, while the explosion pressure decreases, and the ignition delay time is shortened. Moreover, the higher the initial temperature is, the higher the mole fraction of free radicals is.

Abstract: The antioxidant activity of Polyrhachis vicina wine extract was investigated: The IC₅₀ of scavenging effect on superoxide radical generated by Pyrogallol autoxidation was 0.37 mg/mL; the maximum scavenging rate was 81.4%. The IC₅₀ of scavenging effect on hydroxyl free radical generated by Fenton reaction was 0.66 mg/mL; the maximum scavenging rate was 91.8%. The IC₅₀ of DPPH· scavenging effect was 0.48 mg/mL; the maximum scavenging rate was 91.4%. The results indicated that Polyrhachis vicina wine extract showed activity both in scavenging free radicals and antioxidation.