Recent insight into the advances and prospects of microbial lipases and their potential applications in industry

Enzymes play a crucial role in various industrial sectors. These biocatalysts not only ensure sustainability and safety but also enhance process efficiency through their unique specificity. Lipases possess versatility as biocatalysts and find utilization in diverse bioconversion reactions. Presently, microbial lipases are gaining significant focus owing to the rapid progress in enzyme technology and their widespread implementation in multiple industrial procedures. This updated review presents new knowledge about various origins of microbial lipases, such as fungi, bacteria, and yeast. It highlights both the traditional and modern purification methods, including precipitation and chromatographic separation, the immunopurification technique, the reversed micellar system, the aqueous two-phase system (ATPS), and aqueous two-phase flotation (ATPF), moreover, delves into the diverse applications of microbial lipases across several industries, such as food, vitamin esters, textile, detergent, biodiesel, and bioremediation. Furthermore, the present research unveils the obstacles encountered in employing lipase, the patterns observed in lipase engineering, and the application of CRISPR/Cas genome editing technology for altering the genes responsible for lipase production. Additionally, the immobilization of microorganisms' lipases onto various carriers also contributes to enhancing the effectiveness and efficiencies of lipases in terms of their catalytic activities. This is achieved by boosting their resilience to heat and ionic conditions (such as inorganic solvents, high-level pH, and temperature). The process also facilitates the ease of recycling them and enables a more concentrated deposition of the enzyme onto the supporting material. Consequently, these characteristics have demonstrated their suitability for application as biocatalysts in diverse industries.

Transition metal-free C(sp3)-H selenation of β-ketosulfones

The installation of selenium groups has become an essential step across a number of industries such as agrochemicals, drug discovery, and materials. However, direct C(sp3)-H selenation, which is most atom economical, remains a formidable challenge, and only a few examples have been reported to date. In this article, we introduce the transition metal-free C(sp3)-H selenation with the easily available β-ketosulfones and diselenides as the material source. This benign protocol permits access to a broad spectrum of α-aryl(alkyl) seleno-β-ketosulfones in high yields with outstanding functional group compatibility. Distinct advantages of this protocol over all previous methods encompass the utilization of base and air as an oxidant, room temperature, and enhanced green chemistry matrices.

Introduction of Methyl Group in Substituted Isoselenazolones: Catalytic and Mechanistic Study

Copper-catalyzed direct selenation of substituted 2-bromo-N-phenylbenzamide substrates with elemental selenium powder provided a series of methoxy-substituted isoselenazolones via the C-Se and Se-N bond formations. Phenolic substituted isoselenazolones have been obtained by O-demethylation of the corresponding methoxy-substituted analogues using boron tribromide. Some isoselenazolones have been structurally characterized by X-ray single-crystal analysis. The glutathione peroxidase (GPx)-like antioxidant activity of isoselenazolones has been evaluated both in thiophenol and coupled-reductase assays. All isoselenazolones showed good GPx-like activities in the coupled-reductase assay. The ferric-reducing antioxidant power of phenolic antioxidants has also been evaluated. The best phenolic antioxidants were found to be good ferric-reducing antioxidant power agents. The single electron transfer, hydrogen atom transfer, and proton-coupled electron transfer mechanisms for the antioxidant properties of all catalysts have been supported by density functional theory calculations. The catalytic cycle was proposed for one of the phenolic isoselenazolones involving diselenide, selenenyl sulfide, selenol, and selenenic acid as intermediates using ⁷⁷Se{¹H} NMR spectroscopy.

Modulation of the chain-breaking antioxidant activity of phenolic organochalcogens with various co-antioxidants at various pH values

Phenolic organochalcogen chain-breaking antioxidants, i.e. 6-bromo-8 (hexadecyltellanyl)-3,3-dimethyl-1,5-dihydro-[1,3]dioxepino[5,6-c]pyridin-9-ol and 2-methyl-2,3-dihydrobenzo[b]selenophene-5-ol, have been investigated in a two-phase (chlorobenzene/water) lipid peroxidation model system as potent inhibitors of lipid peroxyl radicals with various co-antioxidants at various pH values. The pH has a significant effect on the chain-breaking antioxidant activities of phenolic organochalcogens. The key chain-breaking mechanism profile was attributed to the first oxygen atom transfer from the lipid peroxyl radicals to the Se/Te atom, followed by hydrogen atom transfer in a solvent cage from the nearby phenolic group to the resulting alkoxyl radical. Finally, regeneration of organochalcogen antioxidants could take place in the presence of aqueous-soluble co-antioxidants. Also, in the presence of aqueous soluble N-acetylcysteine at pH 1-7, both antioxidants behaved as very good inhibitors of lipid peroxyl radicals. The role of aqueous soluble mild co-antioxidants in the regeneration studies of organochalcogen antioxidants has been investigated in a two-phase lipid peroxidation model system. The importance of the phase transfer catalyst has been explored in the inhibition studies of selenium containing antioxidants using an Fe(II) source. The overall pH-dependent antioxidant activities of organochalcogens depend on their hydrogen atom transfer ability, relative stability, and distribution in the aqueous/lipid phase.

Stereoselective Reduction of Alkynes: Synthesis of 4-Organoselenyl Quinolines

This study describes the reaction of 2-amino arylalkynyl ketones with organoselenolates to form (Z)-vinyl selenides, which lead to 4-organoselenyl quinolines via an intramolecular condensation. Using the optimized reaction conditions, the generality of this cyclization was studied with various arylalkynyl ketones and diorganyl diselenides. The study of the reaction mechanisms led to the isolation and identification of a vinyl selenide, which was the key intermediate for this cyclization. To expand the structural diversity and to demonstrate the applicability of the 4-organoselenyl quinolines prepared, we studied their application as substrates in the cleavage of the carbon-selenium bond using n-butyllithium followed by the capture of the lithium intermediate by electrophiles and Suzuki and Sonogashira cross-coupling reactions.

Recent Advances in Lipases and Their Applications in the Food and Nutraceutical Industry

Lipases are efficient enzymes with promising applications in the nutraceutical and food industry, as they can offer high yields, pure products under achievable reaction conditions, and are an environmentally friendly option. This review addresses the production of high-value-added compounds such as fatty acid esters, with the potential to be used as flavoring agents or antioxidant and antimicrobial agents, as well as structured lipids that offer specific functional properties that do not exist in nature, with important applications in different food products, and pharmaceuticals. In addition, the most recent successful cases of reactions with lipases to produce modified compounds for food and nutraceuticals are reported.

Selenium as an emerging versatile player in heterocycles and natural products modification

The diverse pharmacological activities of organoselenium compounds are closely correlated to their ability to scavenge and induce reactive oxygen species (ROS), their intrinsic oxidative properties, and their Se(0) release property. The incorporation of selenium into small molecules, and particularly into heterocycles and natural products, has shown great potential in altering the potency and selectivity of these molecules. Therefore, selenium will play an important role in drug discovery in the near future. We summarize how different organoselenium species affect cellular oxidative stress levels, and try to correlate the structural properties of selenium-containing heterocycles and natural product derivatives to their biological activities and therapeutic applications. We also provide some information to guide the rational design of selenium-containing drugs.

Incorporating Selenium into Heterocycles and Natural Products─From Chemical Properties to Pharmacological Activities

Selenium (Se)-containing compounds have emerged as potential therapeutic agents for the treatment of a range of diseases. Through tremendous effort, considerable knowledge has been acquired to understand the complex chemical properties and biological activities of selenium, especially after its incorporation into bioactive molecules. From this perspective, we compiled extensive literature evidence to summarize and critically discuss the relationship between the pharmacological activities and chemical properties of selenium compounds and the strategic incorporation of selenium into organic molecules, especially bioactive heterocycles and natural products. We also provide perspectives regarding the challenges in selenium-based medicinal chemistry and future research directions.

Selenocarbamates as a novel prodrug-based approach towards Carbonic Anhydrase inhibition

A study on the activity of selenocarbamates as a novel chemotype acting as carbonic anhydrase (CA, EC 4.2.1.1) inhibitors is reported. Undergoing CA‐mediated hydrolysis, selenocarbamates release selenolates behaving as zinc binding groups and effectively inhibiting CAs. A series of selenocarbamates characterised by high molecular diversity and complexity have been studied against different human CA isoforms such as hCA I, II, IX and XII. Selenocarbamates behave as masked selenols with potential biological applications as prodrugs for CAs inhibition‐based strategies. X‐ray studies provided insights into the binding mode of this novel class of CA inhibitors.

Synthesis of Nitroarenes by Oxidation of Aryl Amines

Nitro compounds are an important class of organic molecules with broad application in organic synthesis, medicinal chemistry, and materials science. Among the variety of methodologies available for their synthesis, the direct oxidation of primary amines represents an attractive alternative route. Efforts towards the development of oxidative procedures for the synthesis of nitro derivatives have spanned over the past decades, leading to a wide variety of protocols for the selective oxidative conversion of amines to nitro derivatives. Methods for the synthesis of nitroarenes via oxidation of aryl amines, with particular emphasis on recent advances in the field, are summarised in this review.

The Role of Selenium in Pathologies: An Updated Review

Selenium is an essential microelement required for a number of biological functions. Selenium—and more specifically the amino acid selenocysteine—is present in at least 25 human selenoproteins involved in a wide variety of essential biological functions, ranging from the regulation of reactive oxygen species (ROS) concentration to the biosynthesis of hormones. These processes also play a central role in preventing and modulating the clinical outcome of several diseases, including cancer, diabetes, Alzheimer’s disease, mental disorders, cardiovascular disorders, fertility impairments, inflammation, and infections (including SARS-CoV-2). Over the past years, a number of studies focusing on the relationship between selenium and such pathologies have been reported. Generally, an adequate selenium nutritional state—and in some cases selenium supplementation—have been related to improved prognostic outcome and reduced risk of developing several diseases. On the other hand, supra-nutritional levels might have adverse effects. The results of recent studies focusing on these topics are summarized and discussed in this review, with particular emphasis on advances achieved in the last decade.

Electrochemical oxidative cyclization of alkenes, boronic acids, and dichalcogenides to access chalcogenated boronic esters and 1,3-diols

A sustainable, environmentally benign electrochemical oxidative three-component cyclization of allylic alcohols, boronic acids, and dichalcogenides under metal-free and oxidant-free conditions has been developed.

Chalcogenides-incorporating carbonic anhydrase inhibitors concomitantly reverted oxaliplatin-induced neuropathy and enhanced antiproliferative action

Platinum-based chemotherapy is widely used for the treatment of different tumors but is associated with serious side effects, among which neuropathic pain. Carbonic anhydrase (CA, EC 4.2.1.1) inhibitors have recently been validated as therapeutic agents in neuropathic pain and as antitumor agents. We report the synthesis of new organochalcogenides bearing the benzensulfonamide moiety acting as potent inhibitors of several human CA isoforms and, in particular, against hCA II and VII endowed with potent neuropathic pain attenuating effects. Moreover, in combination with cisplatin or doxorubicin, some of the new CA inhibitors enhanced the effects of the anticancer drugs capability in counteracting breast cancer MCF7 cell viability. The concomitant anti-neuropathic pain and antiproliferative effects of the new chalcogenide-based CA inhibitors represent an innovative approach for the counteraction and management of side effects associated with clinically platinum drugs as antitumor agents.

Tellurides bearing benzensulfonamide as carbonic anhydrase inhibitors with potent antitumor activity

We evaluated in vitro a series of telluride containing compounds bearing the benzenesulfonamide group, as effective inhibitors of the physiologically relevant human (h) expressed Carbonic Anhydrase (CA; EC 4.2.1.1) enzymes I, II, IV VII and IX. The potent effects of such compounds against the tumor-associated hCA IX being low nanomolar inhibitors (K_I 2.2 to 2.9 nM) and with good selectivity over the ubiquitous hCA II, gave the possibility to evaluate their lethal effect in vitro against a breast cancer cell line (MDA-MB-231). Among the series, both compounds 3a and 3g induced significant toxic effects against tumor cells after 48 h incubation. Under normoxic condition 3a showed high efficacy killing over 94% of tumor cells at 1 µM, and derivative 3g reached the tumor cell viability under the 5% at 10 µM. In hypoxic condition, these two compounds showed less effective although retained excellent cancer cell killer. These unusual features make them interesting lead compounds acting as antitumor agents also in tumor types not dependent from hCA IX overexpression.

Synthesis of functionalised organochalcogenides and in vitro evaluation of their antioxidant activity

Differently substituted β-hydroxy- and β-amino dialkyl and alkyl-aryl tellurides and selenides have been prepared through ring-opening reactions of epoxides and aziridines with selenium- or tellurium-centered nucleophiles. The antioxidant properties and the cytotoxicity of such compounds have been investigated on normal human dermal fibroblasts. Most of the studied compounds exhibited a low cytotoxicity and a number of them proved to be non-toxic, not showing any effect on cell viability even at the highest concentration used (100 μM). The obtained results showed a significant antioxidant potential of the selected organotellurium compounds, particularly evident under conditions of exogenously induced oxidative stress. The antioxidant activity of selenium-containing analogues of active tellurides has also been evaluated on cells, highlighting that the replacement of Se with Te brought about a significant increase in the peroxidase activity.

Heterotellurium-containing macrocycles towards degradable tellurium-functionalized polymers

We first disclose a facile strategy to synthesize a heterotellurium-containing macrocycle series, and then well-defined degradable poly(telluride-carbonate)s were obtained by ring-opening polymerization.

Unexpected Ethyltellurenylation of Epoxides with Elemental Tellurium under Lithium Triethylborohydride Conditions

The one-pot multistep ethyltellurenylation reaction of epoxides with elemental tellurium and lithium triethylborohydride is described. The reaction mechanism was experimentally investigated. Dilithium ditelluride and triethyl borane, formed from elemental tellurium and lithium triethylborohydride, were shown to be the key species involved in the reaction mechanism. Epoxides undergo ring-opening reaction with dilithium ditelluride to afford β-hydroxy ditellurides, which are sequentially converted into the corresponding β-hydroxy-alkyl ethyl tellurides by transmetalation with triethyl borane, reasonably proceeding through the SH2 mechanism.

Regio- and stereoselective synthesis of new ensembles of diversely functionalized 1,3-thiaselenol-2-ylmethyl selenides by a double rearrangement reaction

The reaction of 2-(bromomethyl)-1,3-thiaselenole with potassium selenocyanate proceeded via a rearrangement with ring expansion, leading to a six-membered 2,3-dihydro-1,4-thiaselenin-2-yl selenocyanate (kinetic product) which in turn underwent rearrangement with ring contraction to a 1,3-thiaselenol-2-ylmethyl selenocyanate (thermodynamic product). These rearrangements occurred by a nucleophilic attack of the selenocyanate anion at two different carbon atoms of the seleniranium intermediate. The efficient regioselective synthesis of alkyl, allyl, 2-propynyl, benzyl, 4-fluorobenzyl, and 2-pyridinylmethyl 1,3-thiaselenol-2-ylmethyl selenides was developed based on the generation of sodium 1,3-thiaselenol-2-ylmethylselenolate from 1,3-thiaselenol-2-ylmethyl selenocyanate or bis(1,3-thiaselenol-2-ylmethyl) diselenide followed by nucleophilic substitution reactions. Sodium 1,3-thiaselenol-2-ylmethylselenolate underwent nucleophilic addition to alkyl propiolates in a regio- and stereoselective manner affording 1,3-thiaselenol-2-ylmethyl vinyl selenides in high yields predominantly with Z-configuration. Not a single representative of the 1,3-thiaselenol-2-ylmethyl selenide scaffold has been previously described in the literature.

Selenolesterase enzyme activity of carbonic anhydrases

Carbonic anhydrases (CAs, E.C. 4.2.1.1) are metalloenzymes expressed on a variety of cell types. Their overexpression leads to serious pathologies, including cancer. The discovery of a series of selenolesters with high structural diversity as novel CA inhibitors is reported here. These compounds show remarkable in vitro inhibition against a panel of human CA isoforms such as hCA I, II, IX and XII. We observed that they undergo a CA mediated hydrolysis, releasing different active selenol fragments, which act as CA inhibitors. Notably, to the best of our knowledge, this is the first example of an enzyme with selenolesterase activity. In addition, X-ray crystallographic data support the proposed mechanism, proving selenolesters as novel pro-drug inhibitors with potential pharmacological applications.

Evaluation of Thio- and Seleno-Acetamides Bearing Benzenesulfonamide as Inhibitor of Carbonic Anhydrases from Different Pathogenic Bacteria

A series of 2-thio- and 2-seleno-acetamides bearing the benzenesulfonamide moiety were evaluated as Carbonic Anhydrase (CA, EC 4.2.1.1) inhibitors against different pathogenic bacteria such as the Vibrio cholerae (VchCA-α and VchCA-β), Burkholderia pseudomallei (BpsCA-β and BpsCA-γ), Mycobacterium tuberculosis (Rv3723-β) and the Salmonella enterica serovar Typhimurium (StCA2-β). The molecules represent interesting leads worth developing as innovative antibacterial agents since they possess new mechanism of action and isoform selectivity preferentially against the bacterial expressed CAs. The identification of potent and selective inhibitors of bacterial CAs may lead to tools also useful for deciphering the physiological role(s) of such proteins.

Electrochemical regioselective selenylation/oxidation of N-alkylisoquinolinium salts via double C(sp2)–H bond functionalization

An efficient and environmentally friendly electrochemical regioselective selenylation/oxidation of N-alkylisoquinolinium salts via double C(sp²)–H bond functionalization has been developed.

Electrochemical diselenylation of indolizines via intermolecular C-Se formation with 2-methylpyridines, α-bromoketones and diselenides

An efficient electrochemical system for the construction of diselenytlated indolizines from available pyridines, ketones and diselenides under undivided electrolytic conditions was developed. No external oxidants and transition-metal catalysts are needed for achieving this three-component tandem reaction realizing C-C, C-N and C-Se bond formations.

Synthesis of novel tellurides bearing benzensulfonamide moiety as carbonic anhydrase inhibitors with antitumor activity

We have synthetized a novel series of β-hydroxy tellurides bearing the benzenesulfonamide group as potent inhibitors of carbonic anhydrase enzymes. In a one pot procedure, we discovered both the ring opening reaction of the three-membered ring and the cleavage of the sulfonamide protecting moiety at the same time. Moreover, the first X-ray co-crystallographic structure of a β-hydroxy telluride derivative with hCA II is reported. The potent effects of these compounds against the tumor-associated hCA IX with low nanomolar constant inhibition values give the possibility to evaluate their activity in vitro using a breast cancer cell line (MDA-MB-231). Compounds 7e and 7g induced significant toxic effects against tumor cells after 48 h incubation in normoxic conditions killing over 50% of tumor cells at 3 μM, but their efficacy decreased in hypoxic conditions reaching the 50% of the tumor cell viability only at 30 μM. These unusual features make them interesting lead compounds to act as antitumor agents, not only as Carbonic Anhydrase IX inhibitors, but reasonably in different pathways, where hCA IX is not overexpressed.

Ring opening reactions of heterocycles with selenium and tellurium nucleophiles

An overview of the preparation and synthetic potentialities of functionalized organoselenium and organotellurium compounds is presented.

Free radical induced selenoxide formation in isomeric organoselenium compounds: the effect of chemical structures on antioxidant activity

Formation of selenoxides improves the antioxidant activity of organoselenium compounds and should be considered as an important marker in the design of new selenium based antioxidants.