Oxygen-radical Capacity Research Articles

Synthesis and characterization of novel blue-emitting nicotinamide-gold nanoclusters with “chain-breaker” antioxidant property

• Synthesis of nicotinamide-reduced gold nanoclusters was optimized. • Molar ratio and pH have dominant role on the formation of blue-emitting nanoclusters. • Fluorescence emission and lifetimes confirm uniform size with few-atomic composition. • These novel clusters possess intense blue fluorescence and antioxidant effect as well. In this paper, we firstly demonstrate a simple and reproducible synthesis protocol to produce nicotinamide-stabilized gold nanoclusters (NAM-Au NCs) under mild conditions. The dominant role of the pH and the ligand to metal ion molar ratio on the formation of these few atomic fluorescent NCs were proven. The prepared NCs show intensive blue-emission at 380 nm with two main lifetime components (4.7 and 6.7 ns), which refers to an ultra-small Au NCs structure and nearly uniform composition. The metallic oxidation state of the metal content was identified by X-ray photoelectron spectroscopy, while infrared studies strongly confirm the binding of aromatic-N and the amide-N to the metal core. The oxygen radical capacity (ORAC) tests were carried out in the case of the stabilizing nicotinamide and the prepared NAM-Au NCs using Trolox molecule as reference between 1 and 100 µM concentration range. Based on the fluorometric measurements, we demonstrated that our blue-emitting Au NCs also possess antioxidant activity with 0.48 ± 0.03 Trolox equivalent value. We clearly proved that our sub-nanometer-sized NAM-Au NCs show novel molecular-like optical features against the pure nicotinamide, but the antioxidant effect was also preserved. These coupled properties make our NCs as potential agents for biocatalytic reactions.

Glutathione peroxidase and subarachnoid hemorrhage: implications for the role of oxidative stress in cerebral vasospasm

Objective: Worldwide, cerebral vasospasm after subarachnoid hemorrhage (SAH) has an estimated morbidity and mortality of 1.2 million annually. While it has long been suspected that reactive oxygen species play a major role in the etiology of cerebral vasospasm after SAH, promising results in animal work were not borne out in human clinical trials, despite intensive research effort. The purpose of this study is to investigate the role of glutathione peroxidase in the SAH cerebrospinal fluid milieu.Methods: We utilized commercially available kits for the quantitation of glutathione peroxidase 1 (glutathione peroxidase) activity and oxygen radical capacity and sodium dodecyl sulfate polyacrylamide gel electrophoresis with Western blotting with specific antibodies to human glutathione peroxidase to determine the enzyme content of the cerebrospinal fluid samples. Human cerebrospinal fluid was obtained in an Institutional Review Board-exempt manner for this study in the following groups: control (no SAH), CSFC (SAH but no vasospasm on angiography) and CSFV (SAH with clinical and angiographic vasospasm).Results: We found that glutathione peroxidase activity is significantly higher in CSFV compared with CSFC, and this is reflected in a higher total oxidative capacity in CSFV. Despite similar levels of glutathione peroxidase protein, CSFV had significantly greater activity than CSFC.Discussion: These results further elucidate previous research from this laboratory, showing increased oxidative stress in CSFV compared with CSFC. In conclusion, there appears to be increased glutathione peroxidase activity in CSFV, despite there being increased levels of oxidative stress markers, suggesting overwhelming oxidative stress may play a role in cerebral vasospasm after SAH.

Steam processed broccoli ( Brassica oleracea) has higher antioxidant activity in chemical and cellular assay systems

Thermally processed fruits and vegetables have long been considered to have a lower nutritional value compared with the fresh produce. This consideration is based on the fact that vitamin C or other thermolabile compounds may lose their activity due to oxidation or in consequences of leaching into the water during home cooking or industrial processing, such as blanching. In this study, broccoli, one of the major agricultural products was exposed to steam; and total antioxidant activity was measured by oxygen radical capacity (ORAC) analysis and a cellular measure of reactive oxygen species (ROS) assay. The study also evaluated the level of total phenolics and total flavonoid content in fresh and steam processed broccoli samples. The result clearly showed that steam-processing elevated the total ORAC (hydrophilic, lipophilic) value by 2.3 fold. Measuring cellular levels of ROS, we found that the hydrophilic part of a steam processed broccoli had a significant reduction of 2,2′-azobis [2-amidinopropane] dihydrochloride (AAPH) induced intracellular ROS level in comparison to that of fresh counterpart. Total phenolic content and total flavonoid content also increased in steamed-processed broccoli. Chromatographic analysis showed that a non-phenolic fraction which appeared unbound on a cosmosil 140 C18 resin contributed 54%, and the phenolic pool eluted by 50–80% methanol contributed 41% of its total increase in ORAC value. Steam processed broccoli gave significant cytoprotection in PC-12 cell line and this neuroprotective efficacy warrant further investigation. This information may have a significant impact on consumers’ food selection, depending on the processing technology used to process agricultural products.

Effect of antioxidant flavonoids and a food mutagen on lymphocytes of a thalassemia patient without chelation therapy in the Comet assay

Thalassemia remains a significant health problem in Europe, the Middle East, and Asia. In such patients, generally high iron levels make free oxygen radicals accessible, for example, through Fenton-type chemistry, and generate superoxide and hydroxyl radicals. Increased oxygen radical capacity is known to be associated with cancer and ageing. It was shown in previous studies that peripheral blood lymphocytes from a sickle/beta thal double heterozygote-sickle phenotype, thalassemia patient, not yet on chelation therapy, were more sensitive to the effects of oxygen radicals and iron salts than lymphocytes from normal controls. Iron overload in thalassemia patients can result from dietary absorption. It was considered that with other dietary agents, such as food mutagens and flavonoids, the thalassemia patient might also show increased sensitivity to the effects of these agents. The present study, therefore, compared the effects of the food mutagen/carcinogen, 3-amino-1-methyl-5H-pyrido(4,3-b)indole (Trp-P-2), in fresh or frozen normal human peripheral lymphocytes with frozen lymphocytes from the same thalassemia patient. The lymphocytes from the thalassemia patient showed an approximately two-fold increase in sensitivity. When a combination of Tryp-P-2, with either quercitin or kaempferol, was compared in frozen lymphocytes and lymphocytes from the thalassemia patient, a two-fold increase in sensitivity was also maintained. Responses to Trp-P-2 were reduced to untreated control levels at the highest doses of quercitin and kaempferol, and were highly significantly different by comparison with Trp-P-2 alone (P<0.001). The flavonoids acted in an antigenotoxic/antioxidant manner. Sensitivity was slightly increased with kaempferol by comparison with quercitin. At low concentrations of the flavonoids there was some evidence of an exacerbation of response, perhaps due to a switch to pro-oxidant status. This exacerbation of response at low doses of flavonoids has been seen in earlier studies with normal lymphocytes. Teratogenesis Carcinog. Mutagen. 21:165-174, 2001.