Ring Hydroxylation Research Articles

Structural Remodeling Mechanism of the Toxic Amyloid Fibrillary Mediated by Epigallocatechin-3-gallate.

Numerous therapeutic agents and strategies were designed targeting the therapies of Alzheimer's disease, but many have been suspended due to their severe clinical side effects (such as encephalopathy) on patients. The attractiveness for small molecules with good biocompatibility is therefore restarted. Epigallocatechin-3-gallate (EGCG), extracted from green tea, is expected to be a promising small-molecule drug candidate, which can remodel the structure of preformed β-sheet-rich oligomers/fibrils and then effectively interfere with neurodegenerative processes. However, as the structure of non-fibrillary aggregates cannot be directly characterized, the atomic details of the underlying inhibitory and destructive mechanisms still remain elusive to date. Here, all-atom molecular dynamics simulations and experiments were carried out to elucidate the EGCG-induced remodeling mechanism of amyloid β (Aβ) fibrils. We showed that EGCG was indeed an effective Aβ fibril inhibitor. EGCG was capable of mediating conformational rearrangement of Aβ1-42 fibrils (from a β-sheet to a random coil structure) and triggering the disintegration of fibrils in a dose-dependent manner. EGCG redirected the structure of Aβ by breaking the β-sheet structure and hydrogen bonds between peptide chains within the Aβ protofibrils, especially the parallel β-strand (L17VFFAEDVGS26). Moreover, reduced solvent exposure and multisite binding patterns all tended to induce the conformation conversion of Aβ17-42 pentameric protofibrils, destroying pre-formed fibrils and inhibiting continued fibril growth. Detailed data analysis revealed that structural features of EGCG with abundant benzene ring and phenolic hydroxyl moieties preferentially interact with the parallel β-strands to effectually hinder the interaction of the interpeptide chain and the growth of the ordered β-sheet structure. Furthermore, experimental studies confirmed that EGCG was able to disaggregate the preformed fibrils and alter the protein structure. This study will enable a deeper understanding of fundamental principles for design of structural-based inhibitors.

Effect of tea polyphenols on sturgeon myofibrillar protein structure in the in vitro anti-glycation model mediated by low temperature vacuum heating

The binding mechanism between tea polyphenols and sturgeon myofibrillar protein (SMP) in the early stage (0, 2, 4 min), middle stage (6, 10 min) and late stage (15 min) of low temperature vacuum heating (LTVH) in an in vitro anti-glycation model was investigated. The result indicated that the protein cross-linking during LTVH treatment were mainly induced by tea polyphenols. The loss rate of free arginine (Arg) and free lysine (Lys) of SMP at the late stage of LTVH treatment (15 min) was 73.95 % and 83.16 %, respectively. The hydrophobic force and disulfide bond were the main force between tea polyphenols and SMP in the middle and late stage of LTVH treatment. The benzene ring and phenolic hydroxyl group of tea polyphenols can interact with the amino acid residues of SMP, which was exothermic and entropy-increasing. This study provides new insights in the interaction mechanisms between tea polyphenols-protein during heat treatment process.

Density functional theory investigation of Cs, Co and Ag separation by functionalised graphene membrane

This work simulates radionuclides enrichment and separation from radioactive wastewater through functionalised porous graphene oxide (PGO) with a six-membered ring hole structure and hydroxyl (-OH) functional groups, using density functional theory (DFT). Cs, Ag, and Co in particular are selected for theoretical simulations in order to better understand the separation mechanism from the radioactive wastewater. The results demonstrate that, except for Co, the adsorption energy of nuclides on PGO membranes is higher than on perfect graphene membranes, and that the adsorption of Ag shifts from physisorption to chemisorption. Cs has a higher energy barrier than Co or Ag. It cannot permeate the PGO membrane and only concentrates on the surface. The separation of Cs from other nuclides using a PGO membranes is attributed mainly to the strong electronic coupling between hydroxyl functional groups and Cs. It is found, in addition, that the adsorption performance of the PGO membranes for Co and Ag decreases with increasing temperature, but has relatively stable adsorption for Cs. These research results demonstrate that a PGO membrane containing six-membered ring holes can effectively screen Cs from radioactive wastewater.

MOF-derived N-Co/Fe-PC composite as heterogeneous electro-Fenton catalysis combined with electrocoagulation process for enhanced degradation of Cu-CIP complexes from wastewater

Recently, heavy metal-antibiotic complexes have been frequently detected in wastewater, posing a serious threat to the human health. In this study, a novel combination of heterogeneous electro-Fenton (hetero-EF) and electrocoagulation process was developed for efficient removal of Cu-ciprofloxacin complexes (Cu-CIP). As hetero-EF cathode catalyst, N doped porous carbon loaded with Co/Fe sites (N-Co/Fe-PC) was innovatively synthesized, and Fe/CoNC structure was formed. The homogeneous mixing of Fe3C and Co3Fe7 resulted in the electron transfer and accumulation on Fe3C, which optimized the active substance and facilitated the oxygen reduction reaction. The effects of current, electrolyte type, pH, and concentration were comprehensively investigated, and the optimum removal efficiency of Cu, CIP, and TOC were 99.69 %, 96.40 %, and 83.62 %, respectively. Besides, it revealed that ·O2– was the dominant contributor to the Cu-CIP degradation. As a result, Cu-CIP complexes were degraded into small molecules and released Cu2+ with the ring-opening demethylation of the piperazine ring, cleavage and demethylation of carboxyl group, hydroxylation of the piperazine ring, and β-cleavage reactions of cyclopropyl group. Meanwhile, they were also adsorbed by aluminum hydroxide/hydroxyl oxides especially γ-AlOOH generated from the anode and finally coprecipitated. This study will provide a novel technology and theoretical basis for enhanced degradation of heavy metal-antibiotic complexes from wastewater.

Alkali-catalyzed hydrothermal oxidation treatment of triclosan in soil: Mechanism, degradation pathway and toxicity evaluation

The continuous accumulation of chlorinated organic pollutants in soil poses a potential threat to ecosystems and human health alike. Alkali-catalyzed hydrothermal oxidation (HTO) can successfully remove chlorinated organic pollutants from water, but it is rarely applied to soil remediation. In this work, we assessed this technique to degrade and detoxify triclosan (TCS) in soil and we determined the underlying mechanisms. The results showed a dechlorination efficiency of TCS (100 mg per kg soil) of 49.03 % after 120 min reaction (H2O2/soil ratio 25 mL·g−1, reaction temperature 180 °C in presence of 1 g·L−1 NaOH). It was found that soil organic constituents (humic acid, HA) and inorganic minerals (SiO2, Al2O3, and CaCO3) suppressed the dechlorination degradation of TCS, with HA having the strongest inhibitory effect. During alkali-catalyzed HTO, the TCS molecules were effectively destroyed and humic acid-like or fulvic acid-like organics with oxygen functional groups were generated. Fluorescence spectroscopy analysis showed that hydroxyl radicals (OH) were the dominant reactive species of TCS degradation in soil. On the basis of the Fukui function and the degradation intermediates, two degradation pathways were proposed. One started with cleavage of the ether bond between the benzene rings of TCS, followed by dechlorination and the opening of benzene via oxidation. The other pathway started with direct hydroxylation of the benzene rings of TCS, after which they were opened and dechlorinated through oxidation. Analysis of the soil structure before and after treatment revealed that the soil surface changed from rough to smooth without affecting soil surface elements. Finally, biotoxicity tests proved that alkali-catalyzed HTO effectively reduced the toxicity of TCS-contaminated soil. This study suggests that alkali-catalyzed hydrothermal oxidation provides an environmentally friendly approach for the treatment of soil contaminated with chlorinated organics such as TCS.

Degradation of oxytetracycline and doxycycline by ozonation: Degradation pathways and toxicity assessment

Tetracyclines are one of the antibiotics widely employed worldwide and frequently detected in surface waters because of incomplete removal from wastewater treatment. Various advanced oxidation processes have been investigated for tetracyclines degradation and their transformation products (TPs) have recently gained more attention. Studies on ozonation are however seldom for the degradation of oxytetracycline (OTC) and doxycycline (DTC). In the present study, a lower O3 inlet gas concentration (4.67 ± 0.13 mg/L), supplied at a flow rate of 0.27 L/min, was shown to be more effective at removing OTC than the same dose of ozone applied at higher inlet gas concentration (up to 6.29 mg/L) over a shorter time at the same flow rate. The use of pCBA and t-BuOH indicated that ozone plays a more important role in the degradation of OTC than HO•. The DTC degradation was less efficient than for OTC, with 99 % removal requiring twice the amount of ozone. OTC had almost no inhibition of Vibrio fischeri, however, the inhibition ratio was increased to 37 % (5-min) and 46 % (15-min) within 1 min of ozonation. Contrastly, DTC had toxic effects on V. fischeri (inhibition rate5min of 84 %) and sustained toxicity in samples treated for up to 40-min. The observed toxicities after treatment could be explained by the identified TPs (26 TPs for OTC and 23 for DTC, some identified for the first time) and their quantitative structure-activity relationship analysis data. Several TPs showed toxic or extremely toxic predicted effects on fish, daphnid, and green algae, corresponding with the V. fischeri inhibition results. Among the possible degradation pathways, aromatic ring hydroxylation and ring-opening pathways could lead to the formation of TPs less harmful to the environment.

Computational molecular interaction between SARS-CoV-2 main protease and theaflavin digallate using free energy perturbation and molecular dynamics

Our objective was to identify the molecule which can inhibit SARS-CoV-2 main protease and can be easily procured. Natural products may provide such molecules and can supplement the current custom chemical synthesis-based drug discovery for this objective. A combination of docking approaches, scoring functions, classical molecular dynamic simulation, binding pose metadynamics, and free energy perturbation calculations have been employed in this study. Theaflavin digallate has been observed in top-scoring compounds after the three independent virtual screening simulations of 598435 compounds (unique 27256 chemical entities). The main protease-theaflavin digallate complex interacts with critical active site residues of the main protease in molecular dynamics simulation independent of the explored computational framework, simulation time, initial structure, and force field used. Theaflavin digallate forms approximately three hydrogen bonds with Glutamate166 of main protease, primarily through hydroxyl groups in the benzene ring of benzo(7)annulen-6-one, along with other critical residues. Glu166 is the most critical amino acid for main protease dimerization, which is necessary for catalytic activity. The estimated binding free energy, calculated by Amber and Schrodinger MMGBSA module, reflects a high binding free energy between theaflavin digallate and main protease. Binding pose metadynamics simulation shows the highly persistent H-bond and a stable pose for the theaflavin digallate-main protease complex. Using method control, experimental controls, and test set, alchemical transformation studies confirm high relative binding free energy of theaflavin digallate with the main protease. Computational molecular interaction suggests that theaflavin digallate can inhibit the main protease of SARS-CoV-2.

Photocatalytic degradation of ketamine using a reusable TiO2/SiO2@Fe3O4 magnetic photocatalyst under simulated solar light

TiO2 heterogeneous photocatalytic processes can carry out efficient abatement of various organic pollutants; however, the difficult recyclability of catalysts largely hinders their application. This study aims to develop a TiO2/SiO2@Fe3O4 core-shell structure magnetic photocatalyst for the degradation of ketamine, a recalcitrant pharmaceutical pollutant commonly found in aquatic environments. The structure and morphology of the TiO2/SiO2@Fe3O4 photocatalyst were comprehensively characterized. Compared with commercial P25 TiO2, the fabricated TiO2/SiO2@Fe3O4 photocatalyst exhibited a higher ketamine degradation efficiency under simulated solar irradiation, with a pseudo-first-order rate constant of 0.1768 min–1 (conditions: [ketamine]0 = 0.3 μM, [TiO2/SiO2@Fe3O4] = 100 mg/L and pH = 7). Additionally, the magnetic TiO2/SiO2@Fe3O4 was easily recovered and showed stable performance, with the ketamine degradation rate only slightly decreasing from 100% to 91% within six cycles of use. The mechanistic investigation demonstrated the participation of •OH, h+ and •O2– in ketamine photocatalytic degradation, with •O2– playing the dominant role. During the photocatalytic pathways of ring opening, oxygen addition, N-demethylation and hydroxylation, ketamine was decomposed into byproducts and further achieved efficient mineralization and detoxification (performed by the Microtox® acute toxicity test), showing the promising potential of TiO2/SiO2@Fe3O4 for use in water purification.

Effect of hapten structures on development of novel antibody against capsaicin and dihydrocapsaicin

• Three novel capsaicinoids haptens were synthesized, and the antibody-eliciting properties of four hapten-protein conjugations were investigated. • Novel polyclonal antibodies against capsaicinoids were prepared, and the important role of molecular structure and electrostatic potential in producing specific antibodies was verified. • A competitive indirect ELISA (icELISA) was established for capsaicinoids detection in spicy foods. Capsaicinoids content as a basis for the evaluation of spicy taste has attracted much attention. Antibody, as an important component of immunoassay, plays an important role in the detection of capsaicinoids levels. The molecular structure of the hapten is the key factor affecting the quality of small molecule antibodies. In our study, six capsaicinoids haptens were selected with different junction arm of length and structure to analyzed immune effect by geometric structure and electrostatic potential (ESP). Among them, three haptens were capsaicinoids structural analogues, and others were designed and synthesized. The results showed that the retention of amide bond (–NH–CO–) and hydroxyl group in the benzene ring of capsaicinoids hapten as well as rigid spacer arm that linked proteins to hapten had a positive effect on the affinity of the antibody. It provided a theoretical basis for rapid screening of small molecular substance haptens. To test our hypothesis, four kinds of haptens were used to synthesize antigens and immunize animals. Comparing 28 antiserum/coating conjugates combinations tested by indirect competitive enzyme-linked immunosorbent assay (icELISA) method for capsaicinoids (i.e., capsaicin and dihydrocapsaicin), the homologous combination of Pa-B2/OVA-hapten B had been shown to be most suitable for the determination of capsaicin and dihydrocapsaicin, which was consistent with the ESP analysis. In short, ESP analysis can speed up haptens screening and reduce the workload while producing high-quality antibodies. Thus, an icELISA based on hapten B polyclonal antibody was developed with IC 50 value of 0.36 μg mL −1 and the limit of detections (LODs) of 20 µg kg −1 in spicy food samples. Moreover, these results were also validated by high performance liquid chromatography (HPLC), and showed good agreements.

Virenscarotins A–M, thirteen undescribed carotane sesquiterpenes from the fungus Trichoderma virens

A document investigation on the fungus Trichoderma virens led to the isolation of thirteen undescribed carotane sesquiterpenes and homologous. All structures were elucidated on the basis of NMR and HRESIMS data, and their absolute configurations were assigned by ECD calculation. Especially, virenscarotins A and B were first ramifications forged by aldol condensation of 4-hydroxy-3-isopentenyl-benzaldehyde with two hydroxyl groups in ring A of traditional carotane sesquiterpenes. Ring rearrangement/expansion and oxidative cleavage of normal carotane sesquiterpenes lead to the six-membered ring A of compound virenscarotin C and the ring A cleavage of compound virenscarotin D. All compounds were evaluated for cytotoxic, anti-inflammatory, and seed germination inhibitory activities.

Metabolism of the synthetic cathinone alpha-pyrrolidinoisohexanophenone in humans using UHPLC-MS-QToF

Alpha-pyrrolidinoisohexanophenone (α-PHiP/α-PiHP) is a synthetic drug structurally related to cathine, a natural psychoactive alkaloid isolated from khat plant. α-PiHP is a structural isomer of α-PHP. α-PHP and α-PiHP may be considered as an analogue of α-PVP, a Schedule I drug under the Convention on Psychotropic Substances by the United Nations. This α-pyrrolidinophenone was first reported to EMCDDA by Slovenia in December 2016. In Hungary it appeared in August 2016 but before 2021 it had been detected in seizures only two times and it had never been identified in biological samples. However, in 2021 its consumption became prevalent in Hungary. α-PiHP was detected in one blood sample and twenty-one urine samples collected during the last two months of 2021 and submitted to our laboratory for forensic toxicological analysis. It means that about 5% of our cases were confirmed positive for α-PiHP during these months. Until February 2022 α-PiHP has been identified in one fatal intoxication case in Poland. This study aims to investigate and rank the in vivo urinary metabolites of α-PiHP. Urinary metabolites of α-PiHP have been investigated by analysing pooled human liver microsome (pHLM) and pooled S9 fraction (pS9) samples in vitro, blank urine samples as negative controls and in vivo urine samples from users ( n = 4) as positive controls using a Waters Xevo G2-XS UHPLC-MS-QToF. The analysis was performed in MSe mode and Unify software was applied to search for metabolites and localize the metabolic transformation according to the fragment ions of the spectra resulted from high energy collisions. Phase I and Phase II metabolites were investigated and ranked according to their relative abundance. In this metabolism study ten in vivo urinary metabolites of α-PiHP were tentatively identified. The identifications were confirmed by use of in vitro metabolites detected in pHLM and pS9 samples. Eight of them were Phase I metabolites and two of them were Phase II metabolites. According to the metabolite ranking study five metabolites were more abundant in urine than the parent compound. For α-PiHP, the two major metabolites via reduction of the keto moiety (M01) and via hydroxylation of the pyrrolidine ring combined with the oxidation of the isoalkyl chain (M06) were identified. The metabolites via the combination of keto reduction and oxidation of the isoalkyl chain (M04), via a ring-opening followed by a caboxylation (M09) and via the glucuronidation of the keto reduced metabolite (M07) were also dominant. The minor metabolites were one Phase II metabolite (M08), two metabolites via oxidation of the isoalkyl chain (M02, M03), one metabolite via the combination of keto reduction and hydroxylation of the pyrrolidine ring (M05) and one metabolite via oxidation of the pyrrolidine ring (M10). As a result of this present study for the urinary metabolites of α-PiHP, its proposed metabolic pathways in humans include reduction of the keto group, oxidation of the isoalkyl chain, oxidation of the pyrrolidine ring to the oxo moiety or ring opening followed by carboxylation, and the combination of these pathways. Finally, it should be pointed out that the detection of relevant metabolites in addition to the parent drug is important for indisputably proving ingestion of the drug. It is especially important in differentiating similar compounds having identical ESI+ fragmentation pattern and very similar retention time but being concerned by different legislation control. Besides, according to the present study the relative abundance for the major metabolites of α-PiHP is much higher than for the parent compound. To sum up, the relevant metabolites are key components in screening and confirmatory methods developed for sensitively and selectively detecting α-PiHP consumption.

Enhancing SDS-PAGE Detection of Dilute Extracellular Polystyrene Degrading Enzymes Expressed by Bacillus megaterium Strain via Centrifugal Freeze Concentration Method

This study aims to enhance the sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) detection and visualization of extracellular polystyrene degrading enzyme expressed by Bacillus megaterium as a result of utilizing polystyrene as a sole carbon source. Dilute polystyrene degrading enzyme expressed in the culture supernatant could not be directly visualized from SDS-PAGE stained with colloidal Coomassie blue stain as it falls below its sensitivity or detection limit level. To overcome this problem, the crude enzyme extract was concentrated via the centrifugal freeze concentration method (cryoconcentration). The extracellular enzyme profiles were determined by SDS-PAGE. The SDS-PAGE analysis of the concentrated enzyme extract revealed 6 visible protein bands ranging in size from 10 to 60 kDa. Three distinct protein bands at approximately 20, 45 and 60 kDa were observed to be highly expressed in the culture supernatant. Polystyrene degrading enzyme extracted from the culture supernatant was closely related to several polymer degrading enzymes which suggest that the extracted enzyme from Bacillus megaterium also belongs to the hydrolase’s enzyme family. GC-MS analysis of the extracted samples significantly contains benzene derivatives due to the breaking down of the long-chain aromatic hydrocarbon polymer. Hydroxylation of the aromatic ring formed phenolic substrate took place which suggests being facilitated by intracellular enzyme hydroxylases. Hence, the biodegradation of polystyrene by Bacillus megaterium was believed to incorporate both intracellular and extracellular enzymes.
 HIGHLIGHTS
 
 Bacillus megaterium strain was first reported to contribute to polystyrene biodegradation
 Polystyrene degrading enzyme expressed by Bacillus megaterium was detected through SDS-PAGE
 Cryoconcentration enhanced SDS-PAGE protein detection
 The protein bands were most distinct visualized at approximately 20, 45 and 60 kDa by SDS-PAGE
 GC-MS analysis detected benzene derivatives which confirmed enzymatic degradation activity
 
 GRAPHICAL ABSTRACT

Hollow C, N-TiO2@C surface molecularly imprinted microspheres with visible light photocatalytic regeneration availability for targeted degradation of sulfadiazine

Novel hollow C, N-TiO2@C surface molecularly imprinted microspheres (HCNTC-SMIPs) with hydrophilicity, reusability, and selectivity were synthesized. The core–shell hollow structure yields large specific surface areas, high surface-to-volume ratios and effective diffusion rate on both inner and outer exposed surfaces. The C, N-TiO2 shell possesses high photo-catalytic decomposition capacity toward the specific pollutants. Moreover, TiO2 acts not only as a photocatalyst but also as a double cross-linker agent of molecularly imprinted to significantly reduce the molar ratio of formaldehyde. The hydrophilic surface imprinted layer provides the recognition sites and specific pore structures. The results showed that HCNTC-SMIPs possessed a high specific surface area of 305.10 m2 g−1 and a good visible light harvesting property with a bandgap of 1.67 eV. This could efficiently suppress the photoelectron-hole recombination, and thereby heightening the photocatalytic degradation of sulfadiazine (SDZ). The photodegradation efficiency of HCNTC-SMIPs can reach 99.25 % within 140 min and 90.00 % after 6 cycles. The HCNTC-SMIPs had a higher kinetic constant (0.01815 min−1) than those of HCNTC (0.00964 min−1) and TiO2 (0.00548 min−1). HCNTC-SMIPs can achieve targeted and efficient SDZ removal, as well as in-situ regeneration. The possible degradation pathways of SDZ primarily includes smiles-type rearrangement, SO2 extrusion, ring hydroxylation, direct oxidation and SN bond cleavage processes based on LC-MS analysis.

Enhancing deep mineralization of refractory benzotriazole via carbon nanotubes-intercalated cobalt copper bimetallic oxide nanosheets activated peroxymonosulfate process: Mechanism, degradation pathway and toxicity

Peroxymonosulfate-based advanced oxidation processes (PMS-AOPs) are effective methods for the degradation of highly toxic and refractory nitrogen-containing heteroatomic pollutants such as benzotriazole (BTA). The construction of catalytic materials with multiple active centers is the key to generating abundant reactive oxygen species (ROS) and achieving high mineralization efficiency in PMS-AOPs. Herein, carbon nanotubes-intercalated cobalt copper bimetallic oxide nanosheets catalyst (CoCuNS@CNTs) was obtained by pyrolysis of two-dimensional (2D) MOF precursor. The degradation rate constant of BTA in CoCuNS@CNTs/PMS system was 4 times higher than that of metal oxide nanosheets catalyst without CNTs, while exhibiting high cycling stability and mineralization efficiency. Serial characterizations demonstrated that CoCu nanosheets was formed by CNTs-induced the directional assembly of metal oxide nanoparticles, which had high graphitization and abundant oxygen vacancies and could greatly facilitated the adsorption and electron transfer between the catalyst, PMS and BTA. Moreover, the doping of Cu species significantly improved PMS utilization and accelerated the Co(III)/Co(II) redox cycle. Both radicals (SO4–• and •OH) and non-radicals (1O2) played a role in CuCoNS@CNTs/PMS system and the contributions of ROS were 72.2%, 11.1% and 16.7%, respectively. Meanwhile, the concentration of key ROS (SO4–•) production increased from 4.76 μM to 8.56 μM compared with cobalt oxide nanosheets (CoNS). Three degradation pathways of BTA were proposed: benzene ring opening, benzene ring hydroxylation and triazole ring dimerization. Finally, the toxicity changes during the degradation process were measured and the toxicity of eleven intermediates was evaluated. This study may provide new insights into the degradation of persistent organic pollutants.

A boric acid functional multi-emission metal organic frameworks-based fluorescence sensing platform for visualization of gallic acid

Gallic acid (GA) is widely applied as antioxidant in food, beverages, health-care products, as well as medicines, quantification detection of GA is essential for human health and quality control in food, drugs and health-care products. Herein, we designed a portable sensing platform by utilizing multi-emission Europium Metal-Organic Frameworks (Eu-MOFs) fluorophore which constructed by the coordination polymerization of europium ions (Eu3+) with 3,5-Dicarboxybenzeneboronic acid (BBDC) for the visual detection of GA. The Eu-MOFs fluorophore displayed red fluorescence with the emission peaks at 454 nm and 615 nm under 270 nm excitation. With the addition of GA, the special covalent structure of the borate ester formed between the phenolic hydroxyl group of benzene ring with the hydroxyl group of the boric acid. The red emission at 615 nm decreased, while the blue emission at 454 nm increased gradually. The highly colorimetric fluorescence provides a significant color change from red to blue and furtherly improves the detection precision, resulting in a visual and rapid detection of GA with a limit of detection (LOD) of 22.0 nM. Furthermore, the Eu-MOFs fluorescent probe applied for visual and quantitative detection of GA combined with smartphone color recognizer in tea and fruit juice samples with the recovery range of 88.34–101.16 %, and the detection results were consistent with high performance liquid chromatography (HPLC) results, which suggest an effective strategy to monitor the food additives for food safety and health guarantee.

QSAR analysis of the partitioning of terpenes and terpenoids into human milk

AbstractStudies have shown that olfactory experience during breastfeeding plays an important role in the later development of certain food preferences in life. Thus, the aim of this study was to predict partitioning of odorous terpenes and terpenoids into breast milk from a predictive QSAR model for drug transfer. A large heterogenous data set based on drugs and their active metabolites that were used to build a QSAR was collected from the literature. Due to the vast structural diversity of these compounds and possibly different mechanisms involved in M/P partitioning, a non‐linear artificial neural network (ANN) model was used to develop a predictive QSAR model. The value of the correlation coefficient of predicted versus experimentally measured M/P values for the final model (14‐2‐1) was high (R = .82). The descriptors selected in the final model (14‐2‐1) belong to 3 main categories: (a) solubility/permeability descriptors (dipole moment, polar surface area, aromatic ring count and hydroxyl group count), (b) reactivity descriptors (i.e. HOMO energy) and (c) shape descriptors (different ring size counts, counts of methyl groups and molecular depth). Results of this study predict that many volatile terpenes from the essential oils are transferred into breast milk selectively. The highest M/P values (>3.5) were predicted for β‐caryophyllene, aromadendrene, alloaromadendrene, and 1,4‐ and 1,8‐cineole, high values for carvacrol (M/P = 3.2), eugenol (M/P = 3.0) and thymol (M/P = 3.6), and moderate values for α‐pinene (M/P = 2.3) and low values (M/P = 0.4) for phellandrene and limonene. Our model helps to explain and expand on the current knowledge of volatile compounds in breast milk by predicting that a variety of volatile terpenoids can be found in breast milk.

Highly sensitive and group-targeting detection of steroid estrogens in water environment using a valid oligonucleotide class-specific editing technique

Steroid environmental estrogens (SEEs) are often coexist in water, require complex analytical techniques for separation and monitoring. However, aptamer-based chemical detection often only recognizes one of them, and the detection of SEEs is still a huge challenge. Herein, a group-targeting aptamer with the ability to recognize SEEs was constructed using efficient oligonucleotide class-specific editing technology, and a photoelectrochemical aptasensor capable of detecting the class of SEEs was established. A quantitative analysis of highly toxic SEEs in the environment and carrying similar core carbon skeleton, including 17β-estradiol, esterone, estriol and ethinylestradiol, was performed. The detection limit was as low as 0.1 nM with a response time of only 15 min. Specifically, this method exhibited high anti-interference with different complex media existing. Combining the theoretical calculations with a variety of spectral experiments, the Π-Π stacking and hydrogen bond synergistic interactions between the photoelectric interface and the three ring structures on SEEs and the hydroxyl group of ring 1 were analyzed in depth. Besides, the conformational changes of loose base helix structure and the free rotation limitation of oligonucleotides after the recognition of SEEs at the molecular level were also elucidated, facilitating the transfer of electrons on the surface of the photoelectrode.

Mechanism of Bonding Reactive Dyes with Copolymer (chloromethyl)oxirane-1H-imidazole cationised Cellulose.

Introducing the cellulose chain cationic groups in the modification process completely changes the charge on the cotton surface from negative to partially or totally positive. That allows the electrostatic attraction and simultaneous exhaustion and fixation of reactive dyes. This reaction can be carried out without salt and alkali at room temperature. Similarly, the reaction between reactive dye and an alone copolymer ([IME]+Cl−) with TLC chromatography was confirmed. The analysis with the use of particle optimisation with MM+ molecular mechanics and quantum-chemical calculations PM3 by the method of all valence orbitals confirmed the experimental results of the high activity of the nucleophile formed on the hydroxyl group in the chain of a modifier. It was found and experimentally confirmed that the reactive dyes during the dyeing process of the cotton cationised with copolymer (chloromethyl)oxirane -1H-imidazole ([IME]+Cl−) create covalent bonds due to a reaction with the hydroxyl group located in the modification agent instead of with the hydroxyl group in the glucopiranose ring. Although the dyeing takes place in very mild conditions, a high degree of setting is achieved, comparable to conventional methods.

Commercially Available Flavonols Are Better SARS-CoV-2 Inhibitors than Isoflavone and Flavones.

Despite the fast development of vaccines, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is still circulating and generating variants of concern (VoC) that escape the humoral immune response. In this context, the search for anti-SARS-CoV-2 compounds is still essential. A class of natural polyphenols known as flavonoids, frequently available in fruits and vegetables, is widely explored in the treatment of different diseases and used as a scaffold for the design of novel drugs. Therefore, herein we evaluate seven flavonoids divided into three subclasses, isoflavone (genistein), flavone (apigenin and luteolin) and flavonol (fisetin, kaempferol, myricetin, and quercetin), for COVID-19 treatment using cell-based assays and in silico calculations validated with experimental enzymatic data. The flavonols were better SARS-CoV-2 inhibitors than isoflavone and flavones. The increasing number of hydroxyl groups in ring B of the flavonols kaempferol, quercetin, and myricetin decreased the 50% effective concentration (EC50) value due to their impact on the orientation of the compounds inside the target. Myricetin and fisetin appear to be preferred candidates; they are both anti-inflammatory (decreasing TNF-α levels) and inhibit SARS-CoV-2 mainly by targeting the processability of the main protease (Mpro) in a non-competitive manner, with a potency comparable to the repurposed drug atazanavir. However, fisetin and myricetin might also be considered hits that are amenable to synthetic modification to improve their anti-SARS-CoV-2 profile by inhibiting not only Mpro, but also the 3′–5′ exonuclease (ExoN).

Oxidation of diclofenac by permanganate: Kinetics, products and effect of inorganic reductants

The large consumption and discharge of diclofenac (DCF) lead to its frequent detection in surface water and groundwater, posing great threats to humans and ecosystems. This study explored the oxidation kinetics of DCF by permanganate (Mn(VII)), and expounded the underlying reason for the unusual pH-dependency that was unclear in previous studies. The kinetics of DCF analogues (i.e., aromatic secondary amines) by Mn(VII) oxidation were comparatively investigated. Then, a tentative kinetic model involving the formation of an intermediate between Mn(VII) and DCF or its analogues was proposed to fit the pH-rate profile. Since DCF contained two chloro groups, and a carboxyl group which could be ionized by negative electrospray ionization, a precursor ionization scanning approach was used for the first time for detection of N-containing chlorinated oxidation products. New degradation pathways of DCF containing ring opening, carboxylation, carbonylation, electrophilic addition, hydroxylation and dehydrogenation were proposed based on the identified oxidation products. Moreover, it was demonstrated that the introduction of various reducing agents such as Mn(II), Fe(II) and bisulfite significantly improved the oxidation kinetics of DCF by Mn(VII). The positive effects of Mn(II) and Fe(II) were mainly attributed to the accelerated formation of MnO2 that acted as a catalyst or co-oxidizer contributing to DCF degradation. The presence of bisulfite caused two-stage kinetics, where a sharp drop of DCF concentration followed by a slowdown of DCF removal. In the first stage, potent reactive manganese species (e.g., Mn(III), Mn(V), and Mn(VI)) and sulfate radical were generated during reaction of bisulfite with Mn(VII), whereas bisulfite was depleted fast due to excess Mn(VII) concentrations and the system became the Mn(VII)/MnO2 system in the second stage. These results provide new insight into reaction mechanism of DCF with Mn(VII) as well as propose a feasible strategy for enhancing the treatment of DCF contaminated water by Mn(VII).