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

Protective effects of sinapic acid against lead acetate-induced nephrotoxicity: a multi-biomarker approach

Lead acetate (PbAc) is one of the top five most dangerous toxic heavy metals, particularly leading to kidney damage and posing serious health risks in both humans and animals. Sinapic acid (SNP) is a naturally occurring flavonoid found in fruits and vegetables that stands out with its antioxidant, anti-inflammatory, and anticancer properties. This is the first study to investigate the effects of SNP on oxidative stress, inflammation, apoptosis, autophagy and endoplasmic reticulum (ER) stress in PbAc-induced nephrotoxicity in rats by biochemical, molecular and histological methods. 35 Spraque dawley rats were randomly divided into five groups of 7 rats each: control, PbAc, SNP (10mg/kg), PbAc + SNP 5, PbAC + SNP 10. PbAc at a dose of 30 mg/kg body weight was administered via oral gavage alone or in combination with SNP (5 and 10 mg/kg body weight) via oral gavage for seven days. While PbAc impaired renal function by increasing serum urea and creatinine levels, SNP decreased these levels and contributed to the improvement in renal function. The administration of SNP reduced oxidative stress by increasing PbAc-induced decreased antioxidant enzyme (SOD, CAT, and GPx) activities and GSH levels, decreasing MDA levels, a marker of increased lipid peroxidation. SNP administration reduced NF-κB, TNF-α, IL-1β, NLRP3, and RAGE mRNA transcription levels, NF-κB, and TNF-α protein levels that are among the PbAc-induced increased inflammation parameters. Decreases in antiapoptotic Bcl-2 and increases in apoptotic Bax, APAF-1, and Caspase-3 due to PbAc exposure, SNP reversed the situation. SNP reduced ER stress caused by PbAc by increasing PERK, IRE1, ATF-6, CHOP, and GRP-78 levels and made it tend to regress. SNP reduced autophagy damage by decreasing the Beclin-1 protein level increased by PbAc. The findings of the present study suggested that SNP attenuates PbAc-induced nephrotoxicity.

Nitrate promoted defluorination of perfluorooctanoic acid in UV/sulfite system: Coupling hydrated electron/reactive nitrogen species-mediated reduction and oxidation

A significantly accelerated defluorination of recalcitrant perfluorooctanoic acid (PFOA) was explored with the co-present nitrate (20 mg L^-1) by UV/sulfite treatment (UV/sulfite-nitrate). The deep defluorination of PFOA and complete denitrification of nitrate were simultaneously achieved in UV/sulfite-nitrate system. At the initial 30 min, PFOA defluorination exhibited an induction period, exactly corresponding to the removal of the co-existed nitrate. Upon the induction period passed, an accelerated removal of PFOA (5 mg L^-1) occurred, nearly 100% defluorination ratio reached within 2 h. Compared with those in UV/sulfite, the kinetics of PFOA decay, defluorination, and transformation product formations were greatly enhanced in UV/sulfite-nitrate system. Reactive nitrogen species (RNS) generated from e_aq^--induced reduction of nitrate were found to play significant roles on the promoted defluorination apart from e_aq^--mediated reductive defluorination. The investigations on solution pH (7.0-11.0) confirmed that the reductive defluorination of PFOA was more efficient under alkaline conditions, however, the presence of nitrate can promote the defluorination even under neutral pH. Theoretical calculations of Fukui function demonstrated that RNS could easily launch electrophilic attack toward H-rich moieties of fluorotelomer carboxylates (FTCAs, C_nF_2n+1-(CH₂)_m-COO^-), more persistent intermediates (formed via H/F exchange), and convert FTCAs into shorter-chain perfluorinated carboxylic acids, thus facilitating the deep defluorination. Along with the analysis on the denitrification products, the liberation of fluoride ions and generated intermediates, possible decomposition pathways were proposed. This work highlights the indispensable synergy from e_aq^-/RNS with integrated reduction and oxidation on PFOA defluorination and will advance remediation technologies of perfluorinated compound contaminated water.

Reactive Nitrogen Species Generated by Gas-Liquid Dielectric Barrier Discharge for Efficient Degradation of Perfluorooctanoic Acid from Water

Perfluorooctanoic acid (PFOA) poses a serious threat to the ecological environment and biological health because of its ubiquitous distribution, extreme persistence, and high toxicity. In this study, we designed a novel gas-liquid dielectric barrier discharge (GLDBD) reactor which could efficiently destruct PFOA. PFOA removal efficiencies can be obtained in various water matrices, which were higher than 98.0% within 50 min, with energy yields higher than 114.5 mg·kWh^-1. It was confirmed that the reactive species including e^-, ONOOH, •NO₂, and hydroxyl radicals (•OH) were responsible for PFOA removal. Especially, this study first revealed the crucial role of reactive nitrogen species (RNS) for PFOA degradation in the plasma system. Due to the generation of a large amount of RNS, the designed GLDBD reactor proved to be less sensitive to various water matrices, which meant a broader promising practical application. Moreover, influential factors including high concentration of various ions and humic acid (HA), were investigated. The possible PFOA degradation pathways were proposed based on liquid chromatograph-mass spectrometer (LC-MS) results and density functional theory (DFT) calculation, which further confirmed the feasibility of PFOA removal with RNS. This research, therefore, provides an effective and versatile alternative for PFOA removal from various water matrices.

A detailed DFT-based study of the free radical scavenging activity and mechanism of daphnetin in physiological environments

Daphnetin, a biologically active coumarin derivative found in plants of the genus Daphne, is a potent antioxidant phenolic compound. The present work describes the mechanisms and kinetics of the HO, NO, HOO, and NO₂ scavenging activities of daphnetin in physiological environments using quantum chemistry calculations. The main antiradical mechanisms have been studied: formal hydrogen transfer (FHT), sequential electron transfer proton transfer (SETPT), sequential proton loss electron transfer (SPLET), and radical adduct formation (RAF). Besides its good HO scavenging activity in physiological environments, daphnetin is expected to exhibit good HOO and NO₂ scavenging activities in water with k_overall = 1.51 × 10⁷ and 4.79 × 10⁸ M^-1s^-1, respectively. The FHT mechanism decides the HO scavenging activity in aqueous solution, as well as HO, HOO, and NO₂ scavenging activities in lipid media, while SPLET is the primary mechanism in water for HOO and NO₂ scavenging activities. The theoretical predictions were found to be in good agreement with the available experimental data, which supports the reliability of the calculations.

Degradation of caffeic acid by dielectric barrier discharge plasma combined with Ce doped CoOOH catalyst

Herein, Ce doped CoOOH was used as the catalyst for caffeic acid (CA) degradation by dielectric barrier discharge (DBD) plasma. The treatment performance and catalytic mechanism were studied by a series of experiments and density functional theory (DFT) simulations. The results show that the doping amounts of Ce significantly influenced the catalytic performance of CoOOH in DBD plasma, and the catalytic effect reached maximum when the molar ratio of Ce to Co was 1:9. CA was 100 % degraded by Ce₁/Co₉OOH/DBD with 10 min treatment, while only 75.6 % of CA was degraded by 10 min DBD treatment. Transformation of O₃ and H₂O₂ to ⋅OH was mainly responsible for the catalytic effect. The content of oxygen vacancies and unsaturated Co (Lewis acid sites) of CoOOH was increased by doping Ce according to the results of experiments and simulations, and the change was conducive to the catalytic reactions. DFT simulations also indicated that DBD generated O₃ and H₂O₂ were decomposed to O atoms, OH groups and free OH by Ce/CoOOH. The presence of reductive species in DBD plasma was confirmed, and ⋅H was a kind of important reactive specie for CA degradation. CA degradation pathway was proposed based on the detected degradation products.

The Roles of Sono-induced Nitrosation and Nitration in the Sono-degradation of Diphenylamine in Water: Mechanisms, Kinetics and Impact Factors

The potential risks of sono-induced nitrosation and nitration side reactions and consequent toxic nitrogenous byproducts were first investigated via sono-degradation of diphenylamine (DPhA) in this study. The kinetic models for overall DPhA degradation and the formation of nitrosation byproduct (N-nitrosodiphenylamine, NDPhA) and nitration byproducts (2-nitro-DPhA and 4-nitro-DPhA) were well established and fitted (R² > 0.98). Nitrosation contributed much more than nitration (namely, 43.3 - 47.3 times) to the sono-degradation of DPhA. The contribution of sono-induced nitrosation ranged from 0.4 to 56.6% at different conditions. The maximum NDPhA formation rate and the contribution of sono-induced nitrosation were obtained at 600 and 200 kHz, respectively, as ultrasonic frequencies at 200 to 800 kHz. Both NDPhA formation rate and the contribution of sono-induced nitrosation increased with increasing power density, while decreased with increasing initial pH and DPhA concentration. PO₄^3-, HCO₃^-, NH₄⁺ and Fe²⁺ presented negative impacts on sono-induced nitrosation in order of HCO₃^- >> Fe²⁺ > PO₄^3- > NH₄⁺, while Br^- exhibited a promoting effect. The mechanism of NDPhA formation via sono-induced nitrosation was first proposed.

Rapid photochemical decomposition of perfluorooctanoic acid mediated by a comprehensive effect of nitrogen dioxide radicals and Fe3+/Fe2+ redox cycle

Developing efficient methods to degrade perfluorochemicals (PFCs), an emerging class of highly recalcitrant contaminants, are urgently needed in recent years, due to their persistence, high toxicity, and resistance to most regular treatment procedures. Here, a UV-photolysis system is reported for efficient mineralization of perfluorooctanoic acid (PFOA) via irradiation of ferric nitrate aqueous solution, where in-situ generating •NO₂ and the effective Fe³⁺/Fe²⁺ redox cycle synergistically play great roles on rapidly mediating the mineralization of PFOA. A fast PFOA removal kinetics with first-order kinetic constants of 2.262 h^-1 is observed at initial PFOA concentration of 5 ppm (50 mL volume), reaching ∼ 92 % removal efficiency within only 0.5-h irradiation. Near-stoichiometric fluoride ions liberation and high total organic carbon (TOC) removal efficiency (∼100 %) further validated the capability for completely destructive removal of PFOA. A tentative pathway for PFOA destruction is proposed. This work, by UV photolysis of abundant existing iron/nitrate-based systems in natural environment, provides an economical, sustainable and highly efficient approach for complete mineralization of perfluorinated chemicals.

Sinapic acid ameliorate cadmium-induced nephrotoxicity: In vivo possible involvement of oxidative stress, apoptosis, and inflammation via NF-κB downregulation

Cadmium (CD), an environmental and industrial pollutant, generates reactive oxygen species (ROS) and NOS responsible for oxidative and nitrosative stress that can lead to nephrotoxic injury, including proximal tubule and glomerulus dysfunction. Sinapic acid (SA) has been found to possess potent antioxidant and anti-inflammatory effects in vitro and in vivo. We aimed to examine the nephroprotective, anti-oxidant, anti-inflammatory, and anti-apoptotic effects of SA against CD-induced nephrotoxicity and its underlying mechanism. Kidney functional markers (serum urea, uric acid, creatinine, LDH, and calcium) and histopathological examinations of the kidney were used to evaluate CD-induced nephrotoxicity. Oxidative stress markers (lipid peroxidation and total protein), renal nitrosative stress (nitric oxide), antioxidant enzymes (catalase and NP-SH), inflammation markers (NF-κB [p65], TNF-α, IL-6, and myeloperoxidase [MPO]), and apoptotic markers (caspase 3, Bax, and Bcl-2) were also assessed. SA (10 and 20mg/kg) pretreatment restored kidney function, upregulated antioxidant levels, and prevented the elevation of lipid peroxidation and nitric oxide levels, significantly reducing oxidative and nitrosative stress. CD upregulated renal cytokine levels (TNF-α, IL-6), nuclear NF-κB (p65) expression, NF-κB-DNA-binding activity, and MPO activity, which were significantly downregulated upon SA pretreatment. Furthermore, SA treatment prevented the upregulation of caspase 3 and Bax protein expression and upregulated Bcl-2 protein expression. SA pretreatment also alleviated the magnitude of histological injuries and reduced neutrophil infiltration in renal tubules. We conclude that the nephroprotective potential of SA in CD-induced nephrotoxicity might be due to its antioxidant, anti-inflammatory, and anti-apoptotic potential via downregulation of oxidative/nitrosative stress, inflammation, and apoptosis in the kidney.