Graphitic carbon nitride and APTES modified advanced electrochemical biosensor for detection of 17β-estradiol in spiked food samples

This work demonstrates a simple and inexpensive electrochemical biosensing pathway for selective and sensitive recognition of 17β-estradiol (E2) in environmental and food samples. The biosensing system is based on graphitic carbon nitride (g-C₃N₄) and a conductive polymer 3-aminopropyltriethoxysilane (APTES). The proposed biosensor shows the ability to detect E2 in attomolar levels within a wide linear logarithm concentration range of 1 × 10⁻⁶ to 1 × 10⁻¹⁸ mol L⁻¹ with a limit of detection (LOD) of 9.9 × 10⁻¹⁹ mol L⁻¹. The selectivity of the developed biosensor was confirmed by conducting the DPV of similarly structured hormones and naturally occurring substances. The proposed biosensor is highly stable and applicable to detect E2 in the presence of spiked food and environmental samples with satisfactory recoveries ranging from 95.1 to 104.8%. So, the designed electrochemical biosensor might be an effective alternative tool for the detection of E2 and other endogenous substances to attain food safety.

This work demonstrates a simple and inexpensive electrochemical biosensing pathway for selective and sensitive recognition of 17β-estradiol (E2) in environmental and food samples.     

Monitoring the heme iron state in horseradish peroxidase to detect ultratrace amounts of hydrogen peroxide in alcohols

Despite the importance of hydrogen peroxide (H₂O₂) in initiating oxidative damage and its connection to various diseases, the detection of low concentrations of H₂O₂ (<10 μM) is still limited using current methods, particularly in non-aqueous systems. One of the most common methods is based on examining the color change of a reducing substrate upon oxidation using UV/Vis spectrophotometry, fluorophotometry and/or paper test strips. In this study, we show that this method encounters low efficiency and sensitivity for detection of ultratrace amounts of H₂O₂ in non-aqueous media. Thus, we have developed a simple, fast, accurate and inexpensive method based on UV/Vis spectrophotometry to detect H₂O₂ in non-aqueous systems, such as alcohols. In this regard, we demonstrate that monitoring the Soret and Q-band regions of high-valent iron-oxo (ferryl heme) intermediates in horseradish peroxidase (HRP) is well suited to detect ultratrace amounts of H₂O₂ impurities in alcohols in the range of 0.001–1000 μM using UV/Vis spectrophotometry. We monitor the optical spectra of HRP solution for the red shift in the Soret and Q-band regions upon the addition of alcohols with H₂O₂ impurity. We also monitor the reversibility of this shift to the original wavelength over time to check the spontaneous decay of ferryl intermediates to the ferric state. Thus, we have found that the ferryl intermediates of HRP can be used for the detection of H₂O₂ in alcohols at μg L⁻¹ levels through via UV/Vis spectrophotometric method.

Despite the importance of hydrogen peroxide (H₂O₂) in initiating oxidative damage and its connection to various diseases, the detection of low concentrations of H₂O₂ (<10 μM) is still limited using current methods, particularly in non-aqueous systems.     

Sweetsop-like α-Fe2O3@CoNi catalyst with superior peroxidase-like activity for sensitive and selective detection of hydroquinone

Hydroquinone (HQ) is poorly degradable in the ecological environment and is highly toxic to human health even at a low concentration. The colorimetric method has the advantages of low cost and fast analysis, which provides the possibility for simple and rapid detection of HQ. In this work, a new colorimetric method has been developed for HQ detection based on a peroxidase-like catalyst, α-Fe₂O₃@CoNi. This sweetsop-like α-Fe₂O₃@CoNi catalyst enables H₂O₂ to produce hydroxyl (˙OH), leading to the oxidization of colorless 3,3′,5,5′-tetramethylbenzidine (TMB) to blue oxTMB. In the presence of HQ, the blue oxTMB is reduced to colorless, which allows for colorimetric detection of HQ in water samples. This method has been validated by detecting HQ in water samples with high selectivity, rapid response, broad detection range (0.50 to 30 μM), and low detection limit (0.16 μM).

A sweetsop-like α-Fe₂O₃@CoNi catalyst with superior peroxidase-like activity was synthesized and successfully applied to the detection of hydroquinone (HQ) based on the colorimetric principle.     

Versiquinazolines L–Q,new polycyclic alkaloids from the marine-derived fungus Aspergillus versicolor

Further chemical examination of a coral-associated fungus Aspergillus versicolor LZD-14-1 by the PHLC-DAD detection resulted in the isolation of six new polycyclic alkaloids, namely versiquinazolines L–Q (1–6). Their structures were determined by extensive analyses of spectroscopic data, including quantum ECD calculation and X-ray single crystal diffraction for the assignment of absolute configurations. Versiquinazoline L bearing a d-Ala residue and versiquinazoline M containing an l-serine residue are rarely found in the fumiquinazoline-type alkaloids, while versiquinazoline P displayed an unusual scaffold with a spiro-γ-lactone. Versiquinazolines P and Q exhibited significant inhibition against thioredoxin reductase (TrxR) with IC₅₀ values of 13.6 ± 0.6 and 12.2 ± 0.7 μM, which showed higher activity than the positive control curcumin (IC₅₀ = 25 μM). The weak cytotoxicity and potent inhibition toward TrxR suggested that versiquinazolines P and Q are potential for microenvironmental regulation of tumor progression and metastasis.

Further chemical examination of a coral-associated fungus Aspergillus versicolor LZD-14-1 by the PHLC-DAD detection resulted in the isolation of six new polycyclic alkaloids, namely versiquinazolines L–Q (1–6).     

Aspect ratio-controlled preparation of α-CaSO4·0.5H2O from phosphogypsum in potassium tartrate aqueous solution

In this study, a simple and efficient strategy is developed to synthesize rod-shaped α-CaSO₄·0.5H₂O crystals with tunable aspect ratio from industrial phosphogypsum only in potassium tartrate aqueous solution at a low temperature. Industrial phosphogypsum can be effectively converted into rod-shaped α-CaSO₄·0.5H₂O crystals with the assistance of potassium tartrate, and the aspect ratio of α-CaSO₄·0.5H₂O crystals gradually decreases from 52 : 1 to 1 : 1 with increasing the concentration of potassium tartrate. The formation process of the rod-shaped α-CaSO₄·0.5H₂O crystals in this system involves the dissolution of CaSO₄·2H₂O and nucleation of α-CaSO₄·0.5H₂O crystals. The tartrate ions from potassium tartrate in this system preferentially bind to (001) and (002) facets of α-CaSO₄·0.5H₂O crystals, inhibiting the growth of α-CaSO₄·0.5H₂O crystals along the c-axis and controlling its morphology and aspect ratio.

The conversion of industrial gypsum to rod-shaped α-CaSO₄·0.5H₂O crystals with tunable aspect ratio in a H₂O system is realized with potassium tartrate.     

Facile stabilization of a cyclodextrin metal–organic framework under humid environment via hydrogen sulfide treatment

Increasing resistance to humid environments is a major challenge for the application of γ-CD-K-MOF (a green MOF) in real-world utilisation. γ-CD-K-MOF–H₂S with enhanced moisture tolerance was obtained by simply treating MOF with H₂S gas. XPS, Raman and TGA characterizations indicated that the H₂S molecules coordinated with the metal centers in the framework. H₂S acting as a newly available water adsorption potential well near the potassium centers protects the metal–ligand coordination bond from attack by water molecules and thus improves the moisture stability of MOF. After 7 days exposure in 60% relative humidity, γ-CD-K-MOF–H₂S retained its crystal structure and morphology, while γ-CD-K-MOF had nearly collapsed. In addition, the formaldehyde uptake tests indicated that γ-CD-K-MOF retain their permanent porosity after interaction with H₂S. This simple and facile one-step strategy would open a new avenue for preparation of moisture stable MOFs for practical applications.

The moisture stable γ-CD-K-MOF was obtained by simply treating MOF with H₂S gas. H₂S acting as new water adsorption sites protected the metal–ligand bonds from water attack and thus enhanced the moisture resistance of γ-CD-K-MOF.     

Control of the stereochemistry of C14 hydroxyl during the total synthesis of withanolide E and physachenolide C

The stereochemical outcome of the epoxidation of Δ_14–15 cholestanes with mCPBA is controlled by the steric bulk of a C17 substituent. When the C17 is in the β configuration, the epoxide is formed in the α face, whereas if the C17 is trigonal (flat) or the substituent is in the α configuration, the epoxide is formed in the β face. The presence of a hydroxyl substituent at C20 does not influence the stereochemical outcome of the epoxidation.

The epoxide configuration in oxidation of C14–C15 alkenes is determined by the configuration of the C17 substituent.     

Copper-catalyzed synthesis of α-ketoamides using water and dioxygen as the oxygen source

The reaction employing H₂O and O₂ as the co-oxygen source in the catalytic synthesis of α-ketoamides is described. This copper-catalyzed reaction is carried out in a tandem manner constituted by the hydroamination of alkyne, hydration of vinyl–Cu complex and subsequent oxidation. Isotope labeling and radical capture experiments reveal that the oxygen atom of α-ketone at α-ketoamides derives from O₂ and the oxygen atom of amide group originates from H₂O.

The reaction employing H₂O and O₂ as the co-oxygen source in the catalytic synthesis of α-ketoamides is described. This Cu-catalyzed reaction is carried out in a tandem manner constituted by hydroamination of alkyne, hydration of vinyl–Cu complex and subsequent oxidation.     

Microbial transformation of mestanolone by Macrophomina phaseolina and Cunninghamella blakesleeana and anticancer activities of the transformed products

The microbial transformation of anabolic androgenic steroid mestanolone (1) with Macrophomina phaseolina and Cunninghamella blakesleeana has afforded seven metabolites. The structures of these metabolites were characterized as 17β-hydroxy-17α-methyl-5α-androsta-1-ene-3,11-dione (2), 14α,17β-dihydroxy-17α-methyl-5α-androstan-3,11-dione (3), 17β-hydroxy-17α-methyl-5α-androstan-1,14-diene-3,11-dione (4), 17β-hydroxy-17α-methyl-5α-androstan-3,11-dione (5), 11β,17β-dihydroxy-17α-methyl-5α-androstan-1-ene-3-one (6), 9α,11β,17β-trihydroxy-17α-methyl-5α-androstan-3-one (7), and 1β,11α,17β-trihydroxy-17α-methyl-5α-androstan-3-one (8). All the metabolites, except 5 and 6, were identified as new compounds. Substrate 1 (IC₅₀ = 27.6 ± 1.1 μM), and its metabolites 2 (IC₅₀ = 19.2 ± 2.9 μM) and 6 (IC₅₀ = 12.8 ± 0.6 μM) exhibited moderate cytotoxicity against the HeLa cancer cell line (human cervical carcinoma). All metabolites were noncytotoxic to 3T3 (mouse fibroblast) and H460 (human lung carcinoma) cell lines. The metabolites were also evaluated for immunomodulatory activity, and all were found to be inactive.

The microbial transformation of anabolic androgenic steroid mestanolone (1) with Macrophomina phaseolina and Cunninghamella blakesleeana has afforded seven metabolites. Some of them have exhibited moderate cytotoxicity against HeLa cancer cell line.     

Decarboxylative aldol reaction of α,α-difluoro-β-ketocarboxylate salt: a facile method for generation of difluoroenolate

We developed a decarboxylative aldol reaction using α,α-difluoro-β-ketocarboxylate salt, carbonyl compounds, and ZnCl₂/N,N,N′,N′-tetramethylethylenediamine. The generation of difluoroenolate proceeded smoothly under mild heating to provide α,α-difluoro-β-hydroxy ketones in good to excellent yield (up to 99%). The α,α-difluoro-β-ketocarboxylate salt was bench stable and easy to handle under air, which realizes a convenient and environmentally friendly methodology for synthesis of difluoromethylene compounds.

A ZnCl₂/N,N,N′,N′-tetramethylethylenediamine complex promoted decarboxylative aldol reaction of α,α-difluoro-β-ketocarboxylate salt with carbonyl compounds has been developed.     

2-Aryl-3-(arylideneamino)-1,2-dihydroquinazoline-4(3H)-ones as inhibitors of cholinesterases and self-induced β-amyloid (Aβ) aggregation: biological evaluations and mechanistic insights from molecular dynamics simulations

A series of 2-aryl-3-(arylideneamino)-1,2-dihydroquinazoline-4(3H)-ones were evaluated as inhibitors of acetylcholinesterase (AChE), butyrylcholinesterase (BuChE) and self-induced β-amyloid (Aβ) aggregation. All the compounds were found to inhibit both forms of cholinesterase (IC₅₀ in the range 4–32 μM) with some selectivity for BuChE. Most of the compounds also showed self-induced Aβ aggregation inhibitory activities, which were comparable or higher than those obtained for reference compounds, curcumin and myricetin. Docking and molecular dynamics (MD) simulation experiments suggested that the compounds are able to disrupt the dimer form of Aβ.

A series of 2-aryl-3-(arylideneamino)-1,2-dihydroquinazoline-4(3H)-ones were evaluated as inhibitors of acetylcholinesterase (AChE), butyrylcholinesterase (BuChE) and self-induced β-amyloid (Aβ) aggregation.     

A nano-sized Cu-MOF with high peroxidase-like activity and its potential application in colorimetric detection of H2O2 and glucose

Peroxidase widely exists in nature and can be applied for the diagnosis and detection of H₂O₂, glucose, ascorbic acid and other aspects. However, the natural peroxidase has low stability and its catalytic efficiency is easily affected by external conditions. In this work, a copper-based metal–organic framework (Cu-MOF) was prepared by hydrothermal method, and characterized by means of XRD, SEM, FT-IR and EDS. The synthesized Cu-MOF material showed high peroxidase-like activity and could be utilized to catalyze the oxidation of o-phenylenediamine (OPDA) and 3,3′,5,5′-tetramethylbenzidine (TMB) in the presence of H₂O₂. The steady-state kinetics experiments of the oxidation of OPDA and TMB catalyzed by Cu-MOF were performed, and the kinetic parameters were obtained by linear least-squares fitting to Lineweaver–Burk plot. The results indicated that the affinity of Cu-MOF towards TMB and OPDA was close to that of the natural horseradish peroxidase (HRP). The as-prepared Cu-MOF can be applied for colorimetric detection of H₂O₂ and glucose with wide linear ranges of 5 to 300 μM and 50 to 500 μM for H₂O₂ and glucose, respectively. Furthermore, the specificity of detection of glucose was compared with other sugar species interference such as sucrose, lactose and maltose. In addition, the detection of ascorbic acid and sodium thiosulfate was also performed upon the inhibition of TMB oxidation. Based on the high catalytic activity, affinity and wide linear range, the as-prepared Cu-MOF may be used for artificial enzyme mimics in the fields of catalysis, biosensors, medicines and food industry.

A Cu-MOF with high peroxidase-like activity was prepared and could be used for colorimetric detection of H₂O₂ and glucose with high selectivity and good linear range (50–500 μM).     

A highly selective and sensitive H2S sensor at low temperatures based on Cr-doped α-Fe2O3 nanoparticles

Cr-doped α-Fe₂O₃ nanoparticles were synthesized by a low-cost and environmentally friendly hydrothermal route. Their gas sensing properties were investigated and the sensor showed high sensitivity and selectivity to H₂S gas. Different Cr doping levels from 0 to 8.0 wt% were studied, and the sensor of 4.0 wt% Cr-doped α-Fe₂O₃ showed the largest response, with a response of 213 to 50 ppm H₂S at 100 °C. The incorporation of Cr ions within α-Fe₂O₃ nanocrystals increases the specific surface area, and promotes the oxidation of H₂S and oxygen adsorption in the air. Thus, the doping of Cr into α-Fe₂O₃ nanostructures would be a promising method for designing and fabricating high performance H₂S gas sensors.

Cr-doped α-Fe₂O₃ nanoparticles were synthesized by one-step hydrothermal reaction and showed high sensitivity and selectivity to H₂S at low temperature.     

Catalyst-free chemoselective α-sulfenylation/β-thiolation for α,β-unsaturated carbonyl compounds

A novel, efficient, catalyst-free and product-controllable strategy has been developed for the chemoselective α-sulfenylation/β-thiolation of α,β-unsaturated carbonyl compounds. An aromatic sulfur group could be chemoselectively introduced at α- or β-position of carbonyls with different sulfur reagents under slightly changed reaction conditions. A series of desired products were obtained in moderate to excellent yields. Mechanistic studies revealed that B₂pin₂ played the key role in activating the transformation towards the β-thiolation of α,β-unsaturated carbonyl compounds. This transition-metal-catalyst-free method provides a convenient and efficient tool for the highly chemoselective preparation of α-thiolation or β-sulfenylation products of α,β-unsaturated carbonyl compounds.

This catalyst-free method provides a useful and efficient tool for the highly chemoselective preparation of α-thiolation or β-sulfenylation products of α,β-unsaturated carbonyl compounds.     

Synthesis of hierarchical nanocrystalline β zeolite as efficient catalyst for alkylation of benzene with benzyl alcohol

To develop an efficient solid acid catalysts for the Friedel–Crafts alkylation reaction, especially for involving bulky molecules, the direct synthesis of hierarchical nanocrystalline β zeolites were achieved by using amphiphilic organosilane ([(CH₃O)₃SiC₃H₆N(CH₃)₂C₁₈H₃₇]Cl, TPOAC) as collaborative structure-directing agent (SDA). The growth evolution of β crystals and the influence of TPOAC/SiO₂ molar ratio on the mesoporous structure, crystal size, and acidic properties of β zeolites were investigated and discussed in detail. The characterization results reveal that intracrystalline mesopores and intercrystalline mesopores/macropores via the stacking of β nanocrystals were generated over the hierarchical β zeolites. Moreover, most of the strong acid sites were well remained compared with the conventional microporous β zeolite. Consequently, the hierarchical nanocrystalline β zeolite synthesized under the optimized synthesis conditions shows improved specific catalytic activity of acid sites (turnover number, TON) in alkylation of benzene with benzyl alcohol, which can be attributed to the integrated balance of considerable mesoporosity, accessibility of the acid sites, and well-remained strong acid sites in the hierarchical β zeolite.

Hierarchical β zeolite with enhanced transport and specific catalytic activity of acid sites in Friedel–Crafts alkylation was achieved by using amphiphilic organosilane surfactant as mesopores-directing agent and crystal growth inhibitor.     

A practical method for the aziridination of α,β-unsaturated carbonyl compounds with a simple carbamate utilizing sodium hypochlorite pentahydrate

The efficient formation of tert-butyl N-chloro-N-sodio-carbamate by the reaction of simple tert-butyl carbamate with sodium hypochlorite pentahydrate (NaOCl·5H₂O) would be a practical and green method for the aziridination of α,β-unsaturated carbonyl compounds. The process described herein is transition-metal free, all of the materials are commercially available, the byproducts (NaCl and H₂O) are environmentally benign and the reaction is stereoselective. The resulting aziridines are potential precursors of amino acids.

The efficient formation of tert-butyl N-chloro-N-sodio-carbamate by the reaction of simple tert-butyl carbamate with sodium hypochlorite pentahydrate would be a practical and green method for the aziridination of α,β-unsaturated carbonyl compounds.     

A H2O2/HBr system – several directions but one choice: oxidation–bromination of secondary alcohols into mono- or dibromo ketones

In this work we found that a H₂O₂–HBr(aq) system allows synthesis of α-monobromo ketones and α,α′-dibromo ketones from aliphatic and secondary benzylic alcohols with yields up to 91%. It is possible to selectively direct the process toward the formation of mono- or dibromo ketones by varying the amount of hydrogen peroxide and hydrobromic acid. The convenience of application, simple equipment, multifaceted reactivity, and compliance with green chemistry principles make the application of the H₂O₂–HBr(aq) system very attractive in laboratories and industry. The proposed oxidation–bromination process is selective in spite of known properties of ketones to be oxidized by the Baeyer–Villiger reaction or peroxidated with the formation of compounds with the O–O moiety in the presence of hydrogen peroxide and Bronsted acids.

Convenience of application, multifaceted reactivity, and compliance with green chemistry principles: H₂O₂–HBr(aq) system for preparation of bromo ketones with yields up to 91%.     

Simultaneous determination of methadone and morphine at a modified electrode with 3D β-MnO2 nanoflowers: application for pharmaceutical sample analysis

The present research synthesized manganese dioxide nano-flowers (β-MnO₂-NF) via a simplified technique for electro-catalytic utilization. Moreover, morphological characteristics and X-ray analyses showed Mn in the oxide form with β-type crystallographic structure. In addition, the research proposed a new efficient electro-chemical sensor to detect methadone at the modified glassy carbon electrode (β-MnO₂-NF/GCE). It has been found that oxidizing methadone is irreversible and shows a diffusion controlled procedure at the β-MnO₂-NF/GCE. Moreover, β-MnO₂-NF/GCE was considerably enhanced in the anodic peak current of methadone related to the separation of morphine and methadone overlapping voltammetric responses with probable difference of 510 mV. In addition, a linear increase has been observed between the catalytic peak currents gained by the differential pulse voltammetry (DPV) of morphine and methadone and their concentrations in the range between 0.1–200.0 μM and 0.1–250.0 μM, respectively. Furthermore, the limits of detection (LOD) for methadone and morphine were found to be 5.6 nM and 8.3 nM, respectively. It has been found that our electrode could have a successful application for detecting methadone and morphine in the drug dose form, urine, and saliva samples. Thus, this condition demonstrated that β-MnO₂-NF/GCE displays good analytical performances for the detection of methadone.

Electrochemical sensor based on β-MnO₂ nanoflower-modified glassy carbon electrode for the simultaneous detection of methadone and morphine was fabricated.     

Lanthanide complexes combined with chiral salen ligands: application in the enantioselective epoxidation reaction of α,β-unsaturated ketones

Readily available lanthanide amides Ln[N(SiMe₃)₂]₃ (Ln = Nd (1), Sm (2), Eu (3), Yb (4), La (5)), combined with chiral salen ligands H₂L^a ((S,S)-N,N′-di-(3,5-disubstituted-salicylidene)-1,2-cyclohexanediamine) and H₂L^b ((S,S)-N,N′-di-(3,5-disubstituted-salicylidene)-1,2-diphenyl-1,2-ethanediamine) were employed in the enantioselective epoxidation of α,β-unsaturated ketones. It was found that the salen–La complex shows the highest efficiency and enantioselectivity. A relatively broad scope of α,β-unsaturated ketones was investigated, and excellent yields (up to 99%) and moderate to good enantioselectivities (37–87%) of the target molecules were achieved.

The enantioselective epoxidation of α,β-unsaturated ketones was catalysed by readily available lanthanide amides La[N(SiMe₃)₂]₃ combined with chiral salen ligands.     

A novel MnO–CrN nanocomposite based non-enzymatic hydrogen peroxide sensor

A MnO–CrN composite was obtained via the ammonolysis of the low-cost nitride precursors Cr(NO₃)₃·9H₂O and Mn(NO₃)₂·4H₂O at 800 °C for 8 h using a sol–gel method. The specific surface area of the synthesized powder was measured via BET analysis and it was found to be 262 m² g⁻¹. Regarding its application, the electrochemical sensing performance toward hydrogen peroxide (H₂O₂) was studied via applying cyclic voltammetry (CV) and amperometry (i–t) analysis. The linear response range was 0.33–15 000 μM with a correlation coefficient (R²) value of 0.995. Excellent performance toward H₂O₂ was observed with a limit of detection of 0.059 μM, a limit of quantification of 0.199 μM, and sensitivity of 2156.25 μA mM⁻¹ cm⁻². A short response time of within 2 s was achieved. Hence, we develop and offer an efficient approach for synthesizing a new cost-efficient material for H₂O₂ sensing.

A MnO–CrN composite was obtained via the ammonolysis of the low-cost nitride precursors Cr(NO₃)₃·9H₂O and Mn(NO₃)₂·4H₂O at 800 °C for 8 h using a sol–gel method.