Hydroxyl Radical Scavenging Effect Research Articles

A novel class of potent antiangiogenic and antioxidant pyrazoles: synthesis, bioactivity, docking and ADMET studies.

Aim: Angiogenesis is the hallmark of cancer progression driven by VEGF/VEGFR-2 signalling pathway, inhibition of which could be a solution to tackle the progression of tumour cells and thus arresting their growth.Materials & methods: A novel class of pyrazoles was synthesized using arginine and dibromo ketones. Antiangiogenic activity was performed by in vivo yolk sac method. Antioxidant activity was evaluated by hydroxyl and superoxide radical scavenging assays. Docking studies were performed to determine the pyrazoles' binding potential with VEGFR-2 receptor and VEGF tyrosine kinase. ADMET properties were calculated using SwissADME and admetSAR for drug-likeness.Results: Compounds 5a-e showed significant antiangiogenic effects. Compound 5f exhibited effective hydroxyl and superoxide radical scavenging activities. Docking results confirmed the potential binding efficiency with VEGFR-2 receptor over VEGF tyrosine kinase, thus, functioning as competitive-inhibitors. ADMET studies revealed that the compounds possess favourable drug-like qualities.Conclusion: This study presents a novel class of pyrazoles as promising antioxidant and antiangiogenic agents with favourable drug-likeness properties.

Bioactive compounds and antioxidant activity in various parts of Morus alba L. Cv. ichinose: a comparative analysis

Present investigation was undertaken to assess the composition of bioactive compounds within various parts of methanolic extracts from mulberry plants utilizing both High-Performance Liquid Chromatography (HPLC) and spectrophotometric methodologies. Furthermore, the antioxidant potential was evaluated through assays including 2,2-diphenyl-1-picrylhydrazyl (DPPH), Ferric Reducing Antioxidant Power (FRAP), β-carotene bleaching (BCBA), and Hydroxyl Radical Scavenging Activity (HRSA). This research incorporated the analysis of the fruit, root, shoot, and leaf of the mulberry (Morus alba L.) Cv. Ichinose. Findings from the investigation revealed that levels of total phenols (533.8 ± 15.6 mg/100 g) and flavonoids (232.3 ± 7.1 mg/100 g) were notably higher in fruit compared to root, while total ascorbic acid content (70.9 ± 3.1 mg/100 g) was significantly elevated in the leaf. The fruit exhibited a significantly higher concentration of total anthocyanins (142.5 ± 3.1 mg/100 g), whereas the leaf contained a substantial amount of total carotenoids (5.8 ± 0.3 mg/100 g). Predominant phenolic acids detected in mulberry included ferulic acid, m-coumaric acid, syringic acid, caffeic acid, chlorogenic acid, and gallic acid. Quercetin and isoquercetin were identified as the major flavonoids in mulberry fruits. In terms of anthocyanins, cyanidin-3-rutinoside (25.6 ± 2.3 mg/100 g) and cyanidin-3-glucoside (16.4 ± 2.1 mg/100 g) were the primary anthocyanins present in the fruit. The main carotenoid found in the leaf was beta-carotene, with levels reaching 2.1 ± 0.3 mg/100 g. Fruit displayed the highest antioxidant activity among all parts examined. Comparison of the EC50 values of fruit (EC50 = 174.2 ± 2.2 µg/mL), root (EC50 = 179.6 ± 2.3 µg/mL), and shoot (EC50 = 189.4 ± 2.1) suggested that these segments of the mulberry plant could potentially function as antioxidants and could exhibit a greater hydroxyl radical scavenging effect than standard antioxidants.

Variation in physicochemical properties and bioactivities of Morinda citrifolia L. (Noni) polysaccharides at different stages of maturity.

Morinda citrifolia L. (Noni) as an evergreen plant is a rich source of natural polysaccharides. The present work aims to investigate the maturation-related changes in polysaccharides of Morinda citrifolia L. (Noni) at five stages of maturity (stages from the lowest to highest degree - 1, 2, 3, 4, and 5). The chemical composition (carbohydrate, protein, uronic acid, and sulfate radical) of Noni polysaccharides was determined by different chemical assays. Ion chromatography system was used to analyze the monosaccharide composition, and the molecular weight was measured by HPGPC. The polysaccharides were also analyzed by FT-IR and their radical scavenging effect against DPPH, hydroxyl radicals and ABTS was evaluated. The UV-vis assay and gel electrophoresis assay were performed to investigate the DNA damage protective effect. Results indicated the significant effect of fruit maturities on the extraction yields, molecular weights, uronic acid contents, sugar levels, monosaccharide compositions and proportions, antioxidant capacities, and DNA protective effects of Noni polysaccharides. However, no fruit maturity stage had prominent impact on the sulfuric radical contents and preliminary structure characteristics. Noni polysaccharides extracted at stage 5 (N5) had the largest extraction yield (8.26 ± 0.14%), the highest sugar content (61.94 ± 1.86%) and the most potent scavenging effect on DPPH (IC50: 1.06 mg/mL) and ABTS (IC50: 1.22 mg/mL) radicals. The stronger DPPH and ABTS radical scavenging activities of N5 might be contributed by its higher content of fucose and rhamnose and smaller molecular weight. Noni polysaccharides extracted at stage 4 (N4) showed the highest uronic acid content (4.10 ± 0.12%), and the superior performance in scavenging hydroxyl radicals and protecting DNA. The greater hydroxyl radical scavenging effect of N4 might be attributed to its higher percentage of the low molecular weight counterpart. Moreover, the DNA protective effects of N4 displayed a positive correlation with its hydroxyl radical scavenging ability. Overall, stage 4 and stage 5 could be ideal stages of fruit maturity aiming at high-quality Noni polysaccharides extraction. This study provided valuable information for the selection of suitable Noni polysaccharides to cater for various industrial applications.

Sensitive colorimetric sensing of glutathione and H2O2 based on enhanced peroxidase mimetic activity of MXene@Fe3O4.

Theperoxidase-like activity of MXene@Fe3O4 nanocomposites and the relevant colorimetric application have been investigatedfor the first time. According to a kinetic study, MXene@Fe3O4 nanocomposites displayed higher peroxidase activity than their individual components, and the catalytic process followed a ping-pong mechanism. The improved peroxidase-like activity of the MXene@Fe3O4 nanocomposites was obtained due to the synergetic impact of the Fe3O4 and MXene phases, the huge ion-accessible interface, and quick electron transfer channels in the nanocomposites. In the presence of hydrogen peroxide (H2O2), the MXene@Fe3O4 nanocomposites can catalyze the reaction of the colorless substrate 3, 3, 5, 5-tetramethylbenzidine (TMB) into oxidized TMB which revealed a blue color at 652nm. After the introduction of glutathione (GSH), the blue color was gradually fading owing to the hydroxyl radical scavenging effect of glutathione. A colorimetric detection platform based on the peroxidase-like activity of the MXene@Fe3O4 nanocomposites was developed for H2O2 and GSH with a detection limit of 0.4μM and 0.5μM, respectively. Thecalibration plot for glutathione detection is calculated by absorbance difference at 652nm, which ranged from 0.5 to 10μM with a detection limit of 0.2μM. The recoveries of GSH with different concentrations ranged from 93.76 to 108.50% and the relative standard deviation from 0.30 to 5.96%. This work significantly extends the application of MXene@Fe3O4 nanocomposites in the construction of colorimetric sensors and reveals a satisfactory result in real sample analysis.

HPLC analysis, acute toxicity and anti-inflammatory effects of Salix alba L. barks extracts on experimental animal models

The white willow, Salix alba L., rich in polyphenols and flavonoids, is traditionally used for its antipyretic, analgesic and anti-inflammatory potential in Algeria. As part of the ethnobotanical survey of medicinal plants in Setif region in Algeria, in the present study, we assessed the safety profile of S. alba barks methanol (SAME) and aqueous (SAQE) extracts, their phytoconstituents, and their antioxidant and anti-inflammatory activities. The in vitro antioxidant activity was evaluated by 2, 2-diphenyl-1-picrylhydrazyl radical (DPPH), reducing power and hydroxyl radical tests assays. HPLC analysis identified 16 compounds in each extract with different concentrations. Gallic acid, syringic acid and cinnamic acid were high in the aqueous extract, while the methanol extracts were rich in chlorogeni cacid, catechin, methyl gallate, pyrocatechol, rutin, ferulic acid, naringenin, taxifolin and kaempferol. The extracts showed significant reducing power, DPPH and hydroxyl radical scavenging effects. In vivo tests showed a strong effect on carrageenan-induced paw edema after 5 h with an inhibition of 88.62 and 87.56% for SAME and SAQE (500 mg/kg), respectively. The extracts also at 500 mg/kg showed significant inhibition of xylene-induced ear edema of 57.81% with SAME 67.18% with SAQE. The results have shown that the methanol and aqueous extracts of the barks of S. alba had no toxic effect on biochemical parameters as well as the organ weights and behaviour. It indicates that S. alba could be a promising source of anti-inflammatory agent.

Efficient extraction, physiochemical, rheological properties, and antioxidant activities of polysaccharides from Armeniaca vulgaris Lam

To improve the extraction efficiency of polysaccharides from Armeniaca vulgaris Lam (APP) by microbial fermentation assisted extraction (MFE), the optimal extraction conditions were optimized as follows: fermentation time, 8 h; rotation speed, 145 r/min; inoculation amount, 8%, and fermentation temperature, 31 °C. When compared to hot water extraction (HWE), the yield of APP increased by 79.77%. Meanwhile, the physical and chemical properties, structural characteristic, rheological, and antioxidant properties of polysaccharides obtained using hot water extraction (APP-H) and microbial fermentation assisted extraction (APP-F) were investigated and compared. These findings revealed that two of the polysaccharides are pectin polysaccharides. APP-F had a lower molecular weight. APP-H and APP-F had the same monosaccharide composition, but different ratio. Furthermore, rheological properties revealed that two polysaccharides had extremely high viscosities. At low concentrations and high frequencies, APP-F had a predominant storage modulus, whereas APP-H had the opposite. Finally, the antioxidant activities of two polysaccharides revealed that APP had a significant difference and APP-F had the highest hydroxyl radical scavenging effect. As a result, microbial fermentation assisted extraction could be an efficient method of extracting APP.

Quercetin as an inhibitor of hemoglobin-mediated lipid oxidation: Mechanisms of action and use of molecular docking

The antioxidant effect of quercetin on hemoglobin(Hb)-mediated lipid oxidation and the mechanisms involved were investigated. Quercetin strongly inhibited Hb-mediated lipid oxidation in washed muscle. Quercetin showed effective hydroxyl radical scavenging ability similar to butylated hydroxytoluene (BHT). Quercetin reduced metHb resulting in formation of oxyHb. Bound quercetin decreased heme dissociation from metHb. Conversion to oxyHb and decreased heme dissociation represent routes to limit Hb-mediated lipid oxidation. Electrospray ionization mass spectrometry (ESI-MS) indicated one molecule of quercetin was covalently bound to Hb α-chain. Quercetin quinone docked 3.3 Å from the thiol of αCys(H15) but not near any other Cys residues of turkey Hb. At the docking site, hydrogen bonding between quercetin quinone and amino acids of α- and β-chain was demonstrated. This represents a path by which quercetin became covalently bound to α-chain. Molecular docking of heme proteins to polyphenols provides a template to better understand antioxidant interactions in muscle foods.

Characterisation of antioxidant peptides from enzymatic hydrolysate of golden melon seeds protein

SummaryThe purpose of present research was to study novel antioxidant peptides from Golden melon seeds. Alkaline protease was used to hydrolyse the Golden melon seeds protein to obtain the hydrolysed peptides. These antioxidant peptides were purified and identified by ultrafiltration, gel filtration chromatography and RP‐HPLC‐ESI‐MS/MS. Results showed that the peptide fraction (GMSHp3) with molecular weight (MW) <3 kDa obtained by ultrafiltration had the highest antioxidant capacity. This fraction was further purified via gel filtration chromatography into six sub‐fractions, among which GMSHp3‐3 exhibited the highest hydroxyl radical scavenging effect. Fraction GMSHp3‐3 was further purified via RP‐HPLC‐ESI‐MS/MS and sequenced as six potential antioxidant peptides with amino acids sequences of RMSFPVMCRN, LMRVLAQLG, ALAPLVALPAA, LVGKPAPD, LPAAHKA and AHAAGYGG, among which LMRVLAQLG, LPAAHKA and AHAAGYGG possessed effective ferric reducing power. These results indicated that novel antioxidant peptides from golden melon seeds protein hydrolysates might be potential antioxidant source of functional foods or nutraceutical supplements.

Abstract LB183: Erythritol acts as tumor enhancer and suppressor depending on concentrations in brain tumor cell lines

Abstract Erythritol (ERT) is a simple four-carbon sugar alcohol, that is produced endogenously via pentose phosphate pathway from glucose in all human cells mainly erythrocytes with a plasma level of ∼9.8 μM. It can be obtained exogenously from diets as an FDA-artificial sweetener. It possesses hydroxyl groups that are responsible for hydroxyl radical scavenging effect (antioxidant property). Recent studies have pointed out an ERT protection based on concentration dependant effect on endothelial cells. The protection includes surviving death under high glucose conditions in diabetic patients. In addition, ERT has been reported in pre-diagnostic serum samples of glioblastoma patients, which was elevated. It was not known whether ERT elevation was defensive or harmful. We studied the cytotoxic activity of ERT on brain tumor cell lines (U87, Daoy) using metabolic activity assay (MTT) with different erythritol concentrations. We observed that on high concentrations (2.87 M, 1.43 M, 0.72 M), there was a significant growth inhibition (P<0.05). On the other hand, lower concentrations (0.36 M, 8 mM, 4 mM, 2 mM, 0.8 mM, 36 µM, 8.2 µM, 4.1µM, 8.2nM), showed growth enhancement. ERT is known with its antioxidant effect in a concentration dependent manner. Therefore, we studied the antioxidant activity of ERT using ROS-Glo H2O2 Assay. We observed that on the high concentrations of ERT there was a significant decrease in hydrogen peroxide concentration to less than 50%, this suggests that ERT has antioxidant effect against hydrogen peroxide. In contrast, low ERT concentrations (around physiological level) showed significant enhancement to tumor growth (P<0.05). In conclusion, we found that erythritol plays an important role in brain cancer development and hydrogen peroxide regulation through a concentration dependant manner. Since ERT is found normally in human plasma, controlling ERT concentration will grant ERT the ability to work as therapeutic enhancer for brain cancer treatment or even a biomarker for prognosis. Citation Format: Rayan Nassani, Hassan AlAmri, Bahauddeen M. Alrfaei. Erythritol acts as tumor enhancer and suppressor depending on concentrations in brain tumor cell lines [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr LB183.

Self-Organized Amphiphiles Are Poor Hydroxyl Radical Scavengers in Fast Photochemical Oxidation of Proteins Experiments.

Analysis of membrane protein topography using fast photochemical oxidation of proteins (FPOP) has been reported in recent years but is still underrepresented in literature. Based on the hydroxyl radical reactivity of lipids and other amphiphiles, it is believed that the membrane environment acts as a hydroxyl radical scavenger decreasing effective hydroxyl radical doses and resulting in less observed oxidation of proteins. We found no significant change in bulk solvent radical scavenging activity upon the addition of disrupted cellular membranes up to 25600 cells/μL using an inline radical dosimeter. We confirmed the nonscavenging nature of the membrane in bulk solution with the FPOP results of a soluble model protein in the presence of cell membranes, which showed no significant difference in oxidation with or without membranes. The use of detergents revealed that, while soluble detergent below the critical micelle concentration is a potent hydroxyl radical scavenger, additional detergent has little to no hydroxyl radical scavenging effect once the critical micelle concentration is reached. Examination of both an extracellular peptide of the integral membrane protein bacteriorhodopsin as well as a novel hydroxyl radical dosimeter tethered to a Triton X-series amphiphile indicate that proximity to the membrane surface greatly decreases reaction with hydroxyl radicals, even though the oxidation target is equally solvent accessible. These results suggest that the observed reduced oxidation of solvent-accessible surfaces of integral membrane proteins is due to the high local concentration of radical scavengers in the membrane or membrane mimetics competing for the local concentration of hydroxyl radicals.

In vitro anti-oxidant and In-vitro anti-diabetic studies of silver, gold and copper nanoparticles synthesized using the flowers of Azhadirachta indica

Nanotechnology industry focuses primarily on promoting nanoscience as a “green” technology to provide a way for less-toxic environmentally benign economic expansion and to synthesize eco- friendly and innocuous drugs to cater to the needs of the contemporary world. An attempt has been made to prepare silver, gold and copper nanoparticles using the aqueous flower extract of Azhadiracta indica (neem). In-vitro anti-oxidant efficacy of these metal nanoparticles (NPs) were investigated through i) Hydrogen atom transfer (HAT) reaction based assays- (ABTS scavenging effect and Hydroxyl radical scavenging effect) and ii) Electron transfer (ET) reaction based assays(DPPH radical scavenging activity and NO free radical scavenging activity). CuNPs exhibits better activity compared to AgNPs and AuNPs. In vitro anti-diabetic test was conducted for all the three NPs through three methods namely inhibition of α- glucosidase enzyme assay, inhibition of alpha amylase enzyme assay and Non-enzymatic glycosylation of hemoglobin assay. CuNPs had a remarkable anti-diabetic activity which was close to the standard acarbose.

Phenolic content and antioxidant activity of ethanolic extracts from Citrus sinensis L. and Citrus reticulata L. fruits

Citrus fruits, in particular the genus Citrus, are very rich in antioxidants which have beneficial effects on human health. The objective of this study was to evaluate the phenolic content and the antioxidant activity of the ethanolic extracts from orange (Citrus sinensis L.) and mandarin (Citrus reticulata L.) fruits. The quantitative estimation of the total phenolic content in the two extracts revealed their richness in these compounds. The results obtained showed that the polyphenols content were 159.66 ± 2.62 mg GAE / g of dry extract and 127.33 ± 2.32 mg GAE / g of dry extract for C. sinensis and C. reticulata, respectively.The quantification of flavonoids content showed that the ethanolic extracts of C. sinensis and C. reticulata contained 0.85 ± 0.01 mg QE / g of dry extract and 0.876 ± 0.073 mg QE / g of dry extract, respectively. Whereas, the tannins contents were 46.32 ± 1.02 mg TAE / g of dry extract for C. sinensis and 47.65 ± 1.36 mg TAE / g of dry extract for C. reticulata. In vitro antioxidant activity was evaluated using two tests: the reducing power and the hydroxyl radical scavenger test. The evaluation of the two extracts by the ferric iron reducing power test showed an EC50 value of 0.882 ± 0.037 mg / ml for C. sinensis extract and an EC50 of 1.085 ± 0.068 mg / ml for C. reticulata extract. In addition, C. sinensis and C. reticulata showed good hydroxyl radical scavenging effect with IC50 values of 0.303 ± 0.026 mg /ml and 0.572 ± 0.100 mg / ml for C. sinensis and C. reticulata, respectively. These results suggested that these fruit extracts could be good sources of phenolic compounds and ingredients with high antioxidant potential.
 Keywords: Citrus sinensis, Citrus reticulata, Polyphenols, Flavonoids, Tannins, Antioxidant activity.

Purification of organic pollutants in cationic thiazine and azo dye solutions using plasma-based advanced oxidation process via submerged multi-hole dielectric barrier discharge

Due to industrialization and population growth, water shortage has emerged as a critical global issue. Pollution of existing water supplies is a critical part of this issue, and organic contaminants are one of the main causes of water pollution. The non-thermal plasma-based advanced oxidation process (AOP) is one of the most widely studied and best developed processes owing to its simple structure and ease of operation. In this study, a plasma-based AOP was stably generated using submerged multi-hole dielectric barrier discharge (DBD) and added to an aqueous solution. Using a plasma system, the complexity of the process for generating hydroxyl radicals (OH) can be simplified by allowing ozone, hydrogen peroxide, ultraviolet light (UV), and OH to be generated simultaneously in one device. The electrical properties and concentrations of the active species were analyzed to establish optimal plasma operating conditions. Among the organic pollutants, methylene blue (MB) and methyl orange (MO) were selected as experimental targets because they are representative cationic thiazine and azo dyes, respectively. The results were analyzed by measuring the absorbance of UV–Vis, total organic carbon (TOC), chromaticity, and changes in solution properties. The effects of hydroxyl radical (OH) scavengers (D-mannitol) on the MB and MO degradation rates were also investigated. Based on these results, degradation mechanisms of MB and MO are proposed. After 3 min of plasma treatment, the concentration, chromaticity, and TOC of MB and MO rapidly decreased. Consequently, we believe that plasma-based AOP using submerged multi-hole DBD has advantages as an alternative technology for treating organic pollutants.

Study of the influence of the matrix characteristics over the photocatalytic ozonation of parabens using Ag-TiO2

Parabens are widely used as antimicrobial and preservative in pharmaceutical and personal products. Their presence has been detected in rivers and wastewater treatment plants. Photocatalytic ozonation process using a low amount of 0.1 wt% Ag-TiO2 proved to be efficient on the degradation of a mixture of five parabens using a low transferred ozone dose (TOD). The pH effect was analyzed under acidic and neutral conditions. Also, the effect of hydroxyl radical scavenger on parabens degradation and on by-products formation was discussed. Hydroxyl radical present a significant role over parabens degradation and also on by-products formation. The reaction mechanism was analyzed using municipal wastewater as a matrix to infer about the behavior of the process at actual conditions. Municipal wastewater as a matrix clearly enhanced the parabens degradation when compared with the case where ultrapure water was used. In fact, the TOD required for total parabens degradation is lowered 10–20 mg/L of TOD. Therefore, to understand the main responsible species for this improvement, the effects of several ions naturally present in wastewater (HCO3−, Cl− and SO42−) were tested. According to the results it seems that sulfate radical improves the process, while chloride and bicarbonate radicals decrease the process efficiency. In terms of toxicity the luminescence inhibition for Vibrio fischeri was analyzed. The inhibition significantly decreased for treated spiked municipal wastewater.

New Insights on the Photodegradation of Caffeine in the Presence of Bio-Based Substances-Magnetic Iron Oxide Hybrid Nanomaterials.

The exploitation of organic waste as a source of bio-based substances to be used in environmental applications is gaining increasing interest. In the present research, compost-derived bio-based substances (BBS-Cs) were used to prepare hybrid magnetic nanoparticles (HMNPs) to be tested as an auxiliary in advanced oxidation processes. Hybrid magnetic nanoparticles can be indeed recovered at the end of the treatment and re-used in further water purification cycles. The research aimed to give new insights on the photodegradation of caffeine, chosen as marker of anthropogenic pollution in natural waters, and representative of the contaminants of emerging concern (CECs). Hybrid magnetic nanoparticles were synthetized starting from Fe(II) and Fe(III) salts and BBS-C aqueous solution, in alkali medium, via co-precipitation. Hybrid magnetic nanoparticles were characterized via X-ray diffraction (XRD), thermo-gravimetric analysis (TGA) and Fourier transform infrared (FTIR) spectroscopy. The effect of pH, added hydrogen peroxide, and dissolved oxygen on caffeine photodegradation in the presence of HMNPs was assessed. The results allow for the hypothesis that caffeine abatement can be obtained in the presence of HMNPs and hydrogen peroxide through a heterogeneous photo-Fenton mechanism. The role of hydroxyl radicals in the process was assessed examining the effect of a selective hydroxyl radical scavenger on the caffeine degradation kinetic.

Antioxidant Activities of Phenolic Metabolites from Flemingia philippinensis Merr. et Rolfe and Their Application to DNA Damage Protection.

F. philippinensis Merr. et Rolfe has been cultivated on a large scale and is widely consumed by local inhabitants as an important nutraceutical, especially against rheumatism which has a deep connection with antioxidants. In this study, a total of 18 different phenolic metabolite compounds in F. philippinensis were isolated and identified, and evaluated for their antioxidant and DNA damage protection potential. The antioxidant activity of the 18 identified compounds was screened using DPPH, ORAC, hydroxyl and superoxide radical scavenging assays. The antioxidant potential of the compounds was found to differ by functionality and skeleton. However, most compounds showed a good antioxidant potential. In particular, seven of the identified compounds, namely, compounds 2, 3, 6, 10, 11, 15 and 16, showed significant protective effects on pBR322 plasmid DNA against the mutagenic and toxic effects of Fenton’s reaction. The most active compound, compound 2, displayed a dose-dependent DNA damage protection potential in the range of 7.5~60.0 μM. The DNA damage protective effect of the identified compounds was significantly correlated with the hydroxyl radical scavenging activity. Compounds that exhibited effective (IC50 = 5.4~12.5 μg/mL) hydroxyl radical scavenging activity were found to be the ones with higher DNA damage protection potential.

A new phenanthrene dimer from Dendrobium palpebrae

A new phenanthrene dimer, namely dendropalpebrone (1), was isolated from the whole plant of Dendrobium palpebre, along with nine known compounds (2–10). All of the isolates were evaluated for their hydroxyl radical scavenging effects using a deoxyribose assay. Dendroflorin (10) showed an appreciable activity, and therefore was selected for further studied in RAW264.7 cells. Compound 10 significantly decreased ROS in H2O2-stimulated RAW264.7 cells in a dose-dependent manner, and improved activity of SOD, GPx, and CAT enzymes.

Protective Mechanism of the Antioxidant Baicalein toward Hydroxyl Radical-Treated Bone Marrow-Derived Mesenchymal Stem Cells.

Our study explores the antioxidant and cytoprotective effects of baicalein and further discusses the possible mechanisms. A methyl thiazolyl tetrazolium (MTT) assay revealed that baicalein could considerably enhance the viability of hydroxyl radical-treated bone marrow-mesenchymal stem cells (bmMSCs) at 37–370 µM. The highest viability rate was 120.4%. In subsequent studies, baicalein was observed to effectively scavenge hydroxyl radical and PTIO• radicals, reducing Fe3+ and Cu2+ ions. In the Fe2+-chelating UV-vis spectra, mixing of baicalein with Fe2+ yielded two evident redshifts (275 → 279 nm and 324 → 352 nm) and a broad absorption peak (λmax ≈ 650 nm, ε = 1.6 × 103 L mol−1·cm−1). Finally, we compared the Fe2+-chelating UV-vis spectra of baicalein and its analogues, including 5-hydroxyflavone, 6-hydroxyflavone, 7-hydroxyflavone, catechol, pyrogallol, and chrysin. This analysis revealed that the 4-keto group of the C-ring played a role. The 5,6,7-trihydroxy-group (pyrogallol group) in the A-ring served as an auxochrome, enhancing the absorbance of the UV-vis spectra and deepening the color of the Fe2+-complex. We concluded that baicalein, as an effective hydroxyl radical-scavenger, can protect bmMSCs from hydroxyl radical-mediated oxidative stress. Its hydroxyl radical-scavenging effects are likely exerted via two pathways: direct scavenging of hydroxyl radicals, possibly through electron transfer, and indirect inhibition of hydroxyl radical generation via Fe2+ chelation through the 4-keto-5,6,7-trihydroxy groups.

Catalytic ozonation of paracetamol on zeolite A: Non-radical mechanism

This study intends to develop removal mechanism of paracetamol during the catalytic ozonation on zeolite4A (Z4A). In order to understand the mechanism on Z4A, degradation of paracetamol, removal of Kjeldhal nitrogen, production of superoxide ion radical and the effect of hydroxyl radical scavenger was studied. The results obtained indicate that, decomposition of paracetamol leads to the decrease in Kjeldhal nitrogen content at considerably higher levels in the case of Z4A/O3 process. The results further revealed that Z4A do not promote the decomposition of ozone leading to the production of superoxide ion radical and hydroxyl radicals. It is therefore, suggested that ozonation process of paracetamol in the presence of Z4A follows a non-radical mechanism.

Photodegradation of novel oral anticoagulants under sunlight irradiation in aqueous matrices

Kinetics of photodegradation of novel oral anticoagulants dabigatran, rivaroxaban, and apixaban were studied under simulated solar light irradiation in purified, mineral, and river waters. Dabigatran and rivaroxaban underwent direct photolysis with polychromatic quantum yields of 2.2 × 10−4 and 4.4 × 10−2, respectively. The direct photodegradation of apixaban was not observed after 19 h of irradiation. Kinetics of degradation of rivaroxaban was not impacted by the nature of the aqueous matrix while photosensitization from nitrate ions was observed for dabigatran and apixaban dissolved in a mineral water. The photosensitized reactions were limited in the tested river water (Isle River, Périgueux, France) certainly due to the hydroxyl radical scavenging effect of the dissolved organic matter. The study of photoproduct structures allowed to identify two compounds for dabigatran. One of them is the 4-aminobenzamidine while the second one is a cyclization product. In the case of rivaroxaban, as studied by very high field NMR, only one photoproduct was observed i.e. a photoisomer. Finally, seven photoproducts were clearly identified from the degradation of apixaban under simulated solar light.