Thermotoga maritima beta-fructosidases are enzymes which release beta-D-fructose from sucrose, raffinose and fructan polymers such as inulin. Surfaces of beta-fructosidases 1UYP and 1W2T from Thermotoga maritima was studied in this work. It was showed that amino acids are distributed not equally on the surfaces of the enzymes. Several clusters of charged and hydrophobic residues were detected at pH 7.0. Such clusters were detected by calculation of distances between them. It was determined that on surfaces of beta-fructosidases PDB ID: 1UYP and PDB ID: 1W2T respectively 96 and 95 % of charged amino acids and also 50 and 42 % of hydrophobic amino acids form clusters. 6 clusters of charged amino acids on surface of beta-fructosidase 1UYP and 5 clusters on surface of beta-fructosidase 1W2T was detected. Composition of such clusters is presented. Both types of beta-fructosidase have 3 clusters of hydrophobic amino acids on their surface. This facts should be considered when choosing immobilization conditions. It was showed that charged matrix is more promising to immobilization of beta-fructosidases 1UYP and 1W2T from Thermotoga maritima due to possibility of binding without significant loss of activity due to overlapping active center. Hydrophobic carriers are less promising due to probable active site overlap. Such binding may have a loss of enzyme activity as a result.

This work was supported by the Ministry of Education and Science of the Russian Federation under state order No. FZGU-2020-0044

The antioxidant potential of phenolic compounds has been extensively investigated because oxidative stress is a hallmark of a variety of human diseases. In this study, we demonstrated antioxidant activity of the molecular hybrids compounds of di-tert-butylphenolic betacalcogenamine in 1,1-diphenyl-2-picryl-hydrazyl (DPPH^•+), 2,2’-azino-bis (3-ethylbenzthiazoline-6-sulfonic acid) (ABTS⁺) radicals scavenging, and ferric ion reducing antioxidant power (FRAP) assays. The compounds N-cyclohexyl-2-(3,5-di-tert-butyl-4-hydroxyphenyl)-2-(N-(2-(phenyltellanyl)ethyl)acetamido)acetamide, and N-(tert-butyl)-2-(3,5-di-tert-butyl-4-hydroxyphenyl)-2-(N-(2-(phenyltellanyl)ethyl)acetamido)acetamide were diluted in dimethylsulfoxide (DMSO) and tested at 0.1 µM, 1 µM, 10 µM, 50 µM and 100 µM concentrations. All in vitro analyses were performed in triplicates and statistically analyzed using one-way ANOVA followed by Tukey’s pos hoc test. Data were presented as mean ± standard error of the mean (SEM), and the statistical significance level was set at p < 0.05. In addition, maximum inhibition (I_Máx) and the half maximal inhibitory concentration (IC₅₀) were calculated. Our data revealed that both compounds had radical scavenging efficiency in the DPPH^•+, and ABTS⁺ assays when compared to control. In addition, in the FRAP assay, the compounds exhibited ferric-reducing ability when compared to control, reinforcing the previous results. These findings show that molecular hybrids compounds of di-tert-butylphenolic betacalcogenamine containing tellurium are promising targets for further studies regarding their antioxidant potential in the treatment of pathophysiology related to oxidative impairment.

Over the years, organodiselenides have emerged as the biologically relevant class of molecules. On one hand, such compounds are known for pro-oxidant effects leading to toxicity in biological systems. On the other hand, there are growing evidences about their bio-mimetic activities as catalysts such as thiol-peroxidase or glutathione peroxidase (GPx)-like activity. Our recent work has explored this paradoxical behavior of diseledides in developing radioprotectors and/or anticancer agents. For this, a number of diselenides of alkyl, nicotinamide and pyridine derivatives have been evaluated in different biological models. The results have shown that diselenides exhibit not only antioxidant effect in cells against radiation damage but can also use the same mechanism to induce cell death in tumor cells [1-3]. Specifically diselenide like 2,2’-dipyridyl diselenide activates biological mechanism of cell cycle perturbation, unfolded protein response and apoptosis in lung cancer (A549) cells through reductive rather than oxidative stress and is based on a shift of the ratio of the thiol redox pairs (GSH and GSSG) on the side of reduction rather than towards oxidation. The cell free studies have indicated that diselenide acts as a substrate of thioredoxin reductase (TrxR) and accordingly it has been postulated that TrxR mediated reduction of diselenides within cells may generate intermediates leading to reductive environment. Additionally, our group has also reported that diselenide compounds can be effective inhibitor of viral proteases, a property useful in developing anti-viral drugs [4]. These finding gain a lot of significance in understanding toxicology and pharmacology of diselenides.

In this work, we present the green Ni-MOF modification by the mechanochemical process in the solvent-free route that has been prepared as hydrogenation catalyst. The zirconium-based metal-organic framework UiO-66 (MOF) at different loading of Ni, were characterized using different techniques including X-ray diffraction (XRD), N₂ porosimetry, X-ray photoelectron spectroscopy (XPS), have been employed for the characterization of the structural, textural, and composition properties of the synthesized materials, respectively. The catalysts have been evaluated in the hydrogenation reaction of methyl levulinate using 2-propanol as a hydrogen donor solvent. The reaction conditions were investigated and established at 30 bar system pressure with a reaction temperature of 200 ◦C using around 0.1 g of catalyst and a flow rate of 0.2 mL/min flow rate of a 0.3 M methyl levulinate solution in 2-propanol. All catalysts employed in this work exhibited good catalytic activities under the investigated conditions, with conversion values in the 30-70% range the selectivity to Υ-valerolactone was 100% for all samples (after one hour time on stream). The highest methyl levulinate conversion and selectivity was achieved by MOF-Ni5% which can be explained by the higher dispersion content of Ni species and the highest accessibility of the Zr sites of the MOF structures even when the superficial area has been reduced.

The enzyme Glutathione Peroxidase (GPx) plays an important role in biological systems reducing the toxic hydrogen peroxide (H₂O₂) to water, using cysteine (Cys) or selenocysteine (Sec) residues. GPx can be inhibited by MeHg, a potent neurotoxin, by the S/Se–HgMe bond formation. We have investigated in silico the dehydroalanine (Dha) formation as the product involved in the possible mechanism of GPx inhibition by MeHg. Cys and Sec bonded to MeHg were modeled at the ZORA- BLYP-D3(BJ)/TZ2P level of theory. In addition, the tellurocysteine (Tec) case was studied for completeness and comparison. Our results demonstrate that the oxidation of MeHg-Cys/Sec/Tec is kinetically more favorable for Tec than Sec and Cys (R–CH–CH₂–XHgMe + H₂O₂ --> R–CH–CH₂–X(O)HgMe + H₂O; X = S, Se, Te; R= (NH₂)(COOH); ΔE^ǂ= 13, 10, and 4 kcal/mol, respectively). Similarly, the intramolecular β-elimination energetics for the Dha formation is more favorable according to the trend S << Se < Te (R–CH–CH₂–X(O)HgMe --> R–C=CH₂ + MeHgXOH; X = S, Se, and Te; R= (NH₂)(COOH); ΔE^ǂ= 13, 4, and 2 kcal/mol; ΔE = 8, -5, and -9 kcal/mol, respectively). Finally, MeHg- lowers the elimination activation energies with respect to alkylated residues Me-Cys/Sec/Tec (ΔE^ǂ= 20, 12, and 11 kcal/mol). The role of Hg and of the different chalcogen atoms on the β-elimination reactions is thoroughly elucidated.

White-rot basidiomycetes are the only microorganisms with the ability to produce both hydrolytic (cellulases and hemicellulases) and oxidative (ligninolytic) enzymes for attacking cellulose/hemicellulose and lignin, while they are also capable of degrading (oxidizing) a wide range of aromatic or toxic compounds. In addition, they produce secondary metabolites with important applications in the cosmetics industry. In the present work, three wild indigenous strains of Basidiomycete fungi (Pleurotus citrinopileatus, Abortiporus biennis and Ganoderma lucidum) were grown in different cultivation media (basal media and agroindustrial residues, such as olive oil mill wastewater, and corn cob). The cultures were examined in regard to the production of biotechnologically relevant enzymes and bioactive compounds. All strains were found to be preferential lignin degraders, in agreement with most known white-rot fungi. Bioinformatic analyses were performed on the proteome of the strains P. citrinopileatus and A. biennis, focusing on CAZymes with biotechnological relevance, and the results were compared with the data from the enzyme activities in the culture supernatants. In terms of secondary metabolism, compounds production and bioactivity of the extracts have been evaluated in relation to the different types of culture media. Principal components analysis (PCA) and volcano plots were generated based on ultra-high-performance liquid chromatography - high resolution mass spectrometry (UHPLC-HRMS) data to reveal significant variations in bioactive compounds amongst the extracellular fluids and fungal biomasses of pilot cultures. Overall, all three Basidiomycete strains were shown to be potent producers of secondary metabolites, but also of oxidative enzymes of special interest for biomass conversion applications.

We developed a promising synthetic methodology for the photo-regioselective 3-selenocyanation of indole employing potassium selenocyanate (KSeCN) and blue LED light, as a green alternative energy source. Derivatives of the indole organoselenium-substituted at the C3 position have emerged as a potentially bioactive molecules and already have demonstrated anti-inflammatory, antinociceptive and anticancer properties. There are in the literature several methodologies described for their preparation, for example, applying intermolecular cyclization with electrophilic selenium species. Therefore, it is of interest to seek innovative, robust and effective methodologies to selectively access this class of molecules.Furthermore, the photocatalytically formed NCSe^• radical can react directly with the N-heterocycle unsaturated substrates, affording the desired compound more effectively than other electrophilic selenium species. In addition, the 3-selenocyanato-1H-indole derivatives can be effective precursors for obtaining diselenides, through a reduction-oxidation sequence. The new method employs indole as unsaturated N-heterocycle substrate, and 1.3 equiv. of potassium selenocyanate, as selenium source, in the presence of 5.0 mol% of eosin Y, an organic photocatalyst, and 1.0 mL of acetonitrile. The system was stirred and irradiated with blue LED light for 5 hours, and the crude was purified using column chromatography. Thus, as a result, we have developed an efficient and smoothly methodology to prepare 3-selenocyanato-1H-indole derivatives, in good yields.

The addition of electrophilic selenium species to alkenes with the formation of a seleniranium intermediate, that reacts with nucleophiles, is one of the most useful method for the formation of new carbon-selenium bonds.¹ Several reagents have been used with the purpose of prepare or generate the electrophilic selenium species, highlighting the catalytic system I₂/DMSO under solvent-free conditions.² This system was successfully employed for the alcoxy-chalcogenylation of alkenes using non-chiral diselenides.³ Herein, we reported a study about the employment of this system in the asymmetric alcoxi-selenyation of styrenes by using chiral non-racemic diselenides and chiral non-racemic alcohols and how it influences on the diastereoisomeric excesses of the products. The desired products were obtained in satisfactory yields and diastereoisomeric excesses under microwave irradiation or conventional heating. The methodology allowed, for example, the preparation of natural products derivatives such as when camphor and menthol were used as alcohols.

References

¹ Tiecco, M.; Testaferri, L.; Santi, C.; Marini, F.; Bagnoli, L.; Temperini, A. a Tomassini, C. Eur. J. Org. Chem. 1998, 2275.

2 Azeredo, J. B.; Godoi, M.; Martins, G. M.; Silveira, C. C. and Braga, A. L. J. Org. Chem., 2014, 79, 4126.

³ Vieira, A. A.; Azeredo, J. B.; Godoi, M.; Santi, C.; da Silva Junior, E. N. and Braga A. L. et. al. J. Org. Chem., 2015, 80, 2120.

Pyrazoles are a privileged class of heteroaromatic compounds and they represent the core motif,¹ in heterocyclic chemistry.²

The presence of the pyrazole nucleus in several structures leads to diversified applications in different areas such as technology, medicine and agriculture. In particular, they are described as inhibitors of protein glycation, antibacterial, antifungal, anticancer, antidepressant, anti-inflammatory, anti-tuberculosis, antioxidant as well as antiviral agents.³

Our contribution in the development of pyrazole derivatives synthesis has been to develop a new method of synthesis of the substituted pyrazole skeleton from the sydnone. Sydnones are considered among the most known mesoionic compounds studied for cycloaddition reactions with alkynes. In this work, a methodology for the 3 + 2 cycloaddition between sydnones and symmetric and non-symmetric alkynes has been developed.

References

1. (a) A. W. Brown, J. P. A. Harrity. Tetrahedron. 2017, 73, 3160; (b) A. Ansari, A. Ali, M. Asif. New J. Chem. 2017, 41, 16; (c) C. Lamberth. Heterocycles. 2007, 71, 1467.
2. L. Browne, J. F. Vivat, A. Plant, E. G. Bengoa, J. P. A. Harrity. J. Am. Chem. Soc. 2009, 131, 7762.
3. (a) K. Karrouchi, S. Radi, Y. Ramli, J. Taoufik, Y. N. Mabkhot, F. A. Al-aizari and M. Ansar. Molecules. 2018, 23, 134; (b) S. Fustero, M. S. Roselló, P. Barrio, A. S. Fuentes. Rev. 2011, 111, 6984; (c) A. Ansari, A. Ali, M. Asif. New J. Chem. 2017, 41, 16.

Organocalcogenides, in particular, organoselenium compounds have been widely studied due to the large number of synthetic and biological applications. Among organoselenium compounds, a class of bis-selenide-alkene derivatives has attracted attention. Recently, some studies have been developed to the synthesis of vinyl chalcogen derivatives, since these are also highly valuable intermediates in several synthetic applications. However, the methodologies developed so far have extensive reaction times, use of toxic solvents and heavy metals. Therefore, there is an emerging need to develop protocols for the synthesis of these molecules that are in accordance with the principles of green chemistry. In this work, we developed an alternative synthesis of bis-selenium-alkene derivatives, through an environmentally appropriate methodology. Reaction optimization was evaluated from the diphenylacetylene and diphenyl diselenide, using I₂/DMSO as a catalytic system under microwave irradiation or conventional heating. The variations of these conditions were carried out through different equivalences between the reagents, the amount of catalyst (I₂), temperature, DMSO and the reaction process (MW or conventional). Even now, it was found that the best established condition was using diphenylacetylene, diphenyl diselenide, 30mol% I₂ in DMSO, under conventional heating at 100°C for 10min. In this condition the product was obtained in 82% yield and its characterization was performed using ¹H and ¹³C NMR spectroscopy. Therefore, the methodology that is being developed, in addition to perfectly attending to the principles of green chemistry, will allow to evaluate the reaction scope using different alkenes and diselenides or even disulfides and ditellurides.