Isolation of Unusual N-Thiophenyl Ebselenamines and other Intermediates during the 77Se NMR Mechanistic Study of Azo-Bis-Ebselen: Their Antioxidant Behaviour against Oxidative Stress

Based on the traditional 77Se NMR spectroscopy investigation, a catalytic cycle for the formation of N-thiophenyl ebselenamine 12 involving diselenide 9, selenenyl sulfide 10 and ebselenamine 7a was reported by the reaction of azo-bis-ebselen 8 with PhSH and H2O2. The signals detected in the 77Se NMR spectrum corresponding to 7a, 10 and 12 were directly isolated from the NMR mixture. Mechanistic investigation for the formation of N-thiophenyl ebselenamine 12 was confirmed from an independent reaction of diselenide 9 and PhSSPh in the presence of H2O2. This was further supported by another diselenide 19 containing p-tolyl group with equimolar amount of H2O2 and PhSH in an independent experiment followed by the 77Se NMR spectroscopy, yielding similar observations. These results, which illustrated diselenide has been observed as the main precursor in the formation of all intermediates. The new novel selenium antioxidants quenched lipidperoxyl radicals much more efficiently than α-tocopherol and were regenerable by the aqueous ascorbic acid in a two-phase (chlorobenzene/water) azo-initiated peroxidation system. The notable benefit of the organoselenium biology, the novel ebselenamine analogues and their corresponding selenenyl sulfides were found to mimic the activity of the glutathione peroxidase enzymes better than ebselen in the coupled reductase assay.

PHYSIOLOGICAL QUALITY AND ANTIOXIDANT ENZYMATIC ACTION IN SUNFLOWER SEEDS EXPOSED TO DETERIORATION1

ABSTRACT This work aimed to evaluate the physiological and biochemical changes resulting from controlled deterioration in different lots of sunflower seeds. Two sunflower seed lots of the cultivar Hélio 253 were subjected to simulated deterioration, using the accelerated aging test methodology (41 °C and 100% RH) for 0, 48, 72, and 96 h. Then, the seeds were subjected to the tests of germination, first germination count, seedling length and dry matter, emergence, accelerated aging, electrical conductivity, and total seedling length. The antioxidant activity was evaluated through the enzymes superoxide dismutase (SOD), ascorbate peroxidase (APX), and peroxidase (POX) at 0, 2, 4, and 6 days after sowing. Deterioration caused a reduction in the germination and vigor of the seeds, mainly in the lot with lower initial vigor and for the longest exposure times (72 and 96 h). For both lots, reductions in SOD activity and increases in POX and APX were observed during seed germination, mainly after 48 h of exposure to aging deterioration. Peroxidase enzymes are activated in deteriorated and non-deteriorated sunflower seeds, mainly after two days of germination.

Effect of oxalic acid on vase life and antioxidative activities of ‘Mero Star’ cut lily flowers

Lily (Lilium L. hybrids) is sub-tropical cut flower that can be grown in open place or in green house and has consumer demand in local as well as in offshore markets. Short vase life, postharvest decay of flowering petals, activities of oxidative enzymes, malondialdehyde contents, electrolyte leakage and low water ratio are the main problems in marketing of cut lilies. This study was carried out to investigate the effect of oxalic acid (OA) treatments on vase life (12 days) and postharvest quality of ‘Mero Star’ cut lily flowers. The flowering stems were placed in 2, 4 and 6% aqueous solution of OA for 12 days at 20±2 °C with 70±5% relative humidity. Flowers placed in 6% OA solution exhibited longest vase life and flower diameter with higher relative water content and increased fresh weight and reduced flower decay. Reduced malondialdehyde contents and electrolyte leakage with higher activities of catalase, superoxide dismutase and peroxidase enzymes were also noted in 6% OA-treated flowers. In conclusion, exogenous postharvest application of 6% OA extended vase life and maintained postharvest quality of cut flowers by reducing electrolyte leakage and malondialdehyde contents with higher antioxidative enzymes activities.

Mineralization of Melanoidin by H₂O₂ Producing Enzymes from Marine Cyanobacteria Oscillatoria boryana BDU 92181

Intracellular enzymes of Oscillatoria boryana BDU 92181 exhibited mineralizing activity on melanoidin, a recalcitrant pigment present in the distillery wastewater. Melanoidin decolourization was postulated to be due to the production of hydrogen peroxide and molecular oxygen released by the cyanobacterium during photosynthesis. The present study was aimed to find out the efficacy of the marine cyanobacterium O. boryana BDU 92181 in producing H2O2 and enzymes involved in hydrogen peroxide production with a view to utilize its potential for decolorization of melanoidin pigment in the distillery effluent. The enzymes involved in the melanoidin degradation have not so far been attempted with cyanobacteria. The results obtained in the present work suggested the activity of the glucose oxidase and Manganese peroxidase enzymes in a marine cyanobacterium Oscillatoria boryana BDU 92181 and whose activity was found to be enhanced in the presence of melanoidin.

Investigating the roles of Listeria monocytogenes peroxidases in growth and virulence

Bacteria have necessarily evolved a protective arsenal of proteins to contend with peroxides and other reactive oxygen species generated in aerobic environments. Listeria monocytogenes encounters an onslaught of peroxide both in the environment and during infection of the mammalian host, where it is the causative agent of the foodborne illness listeriosis. Despite the importance of peroxide for the immune response to bacterial infection, the strategy by which L. monocytogenes protects against peroxide toxicity has yet to be illuminated. Here, we investigated the expression and essentiality of all the peroxidase-encoding genes during L. monocytogenes growth in vitro and during infection of murine cells in tissue culture. We found that chdC and kat were required for aerobic growth in vitro, and fri and ahpA were each required for L. monocytogenes to survive acute peroxide stress. Despite increased expression of fri, ahpA, and kat during infection of macrophages, only fri proved necessary for cytosolic growth and intercellular spread. In contrast, the proteins encoded by lmo0367, lmo0983, tpx, lmo1609, and ohrA were dispensable for aerobic growth, acute peroxide detoxification, and infection. Together, our results provide insight into the multifaceted L. monocytogenes peroxide detoxification strategy and demonstrate that L. monocytogenes encodes a functionally diverse set of peroxidase enzymes.

Физико-химические свойства и антиоксидантная активность наночастиц оксида церия, стабилизированных мальтодекстрином

The study on physicochemical properties of maltodextrin-coated cerium oxide nanoparticles was carried out. The surface structure and properties of CeO2 nanoparticles were investigated. The ability of CeO2 nanoparticles to perform the functions of catalase and peroxidase enzymes, as well as to inactivate hydroxyl radicals was shown.