Polyoxygenated dihydropyrano[2,3-c]pyrrole-4,5-dione derivatives from the marine mangrove-derived endophytic fungus Penicillium brocae MA-231 and their antimicrobial activity

A new polyoxygenated dihydropyrano[2,3-c]pyrrole-4,5-dione derivative, pyranonigrin F (1), together with a related known compound, pyranonigrin A (2), were isolated and identified from Penicillium brocae MA-231, an endophytic fungus obtained from the fresh tissue of the marine mangrove plant Avicennia marina. The structures of these metabolites were determined based on comprehensive spectral interpretation and the absolute configuration of compound 1 was established by X-ray crystallographic analysis. Compounds 1, and 2 showed potent activity against a broad spectrum of human-, aqua-, and plant-pathogens.     

Oxidative Addition of Haloheteroarenes to Palladium(0): Concerted versus SNAr‐Type Mechanism

The kinetics of the oxidative additions of haloheteroarenes HetX (X=I, Br, Cl) to [Pd⁰(PPh₃)₂] (generated from [Pd⁰(PPh₃)₄]) have been investigated in THF and DMF and the rate constants have been determined. In contrast to the generally accepted concerted mechanism, Hammett plots obtained for substituted 2‐halopyridines and solvent effects reveal a reaction mechanism dependent on the halide X of HetX: an unprecedented S_NAr‐type mechanism for X=Br or Cl and a classical concerted mechanism for X=I. These results are supported by DFT studies.     

Single-Molecule Sensing of Acidic Catecholamine Metabolites Using a Programmable Nanopore

Acidic catecholamine metabolites, which could serve as diagnostic markers for many diseases, demonstrate an importance of accurate sensing. However, they share a highly similar chemical structure, which is a challenge in the design of sensing strategies. A nanopore may be engineered to sense these metabolites in a single molecule manner. To achieve this, a recently developed programmable nano-reactor for stochastic sensing (PNRSS) technique adapted with a phenylboronic acid (PBA) adaptor was applied. Three acidic catecholamine metabolites, including 3,4-dihydroxyphenylacetic acid (DOPAC), 3,4-dihydroxymandelic acid (DHMA) and 3-methoxy-4-hydroxymandetic acid (VMA) were investigated by PNRSS. Specifically, DHMA, which contains an α-hydroxycarboxylate moiety and an adjacent cis-hydroxyl groups on its benzene ring, reports two binding modes simultaneously resolvable by PNRSS. Assisted with the high resolution of PNRSS, direct regulation of these two binding modes by pH can also be observed. A custom machine learning algorithm was also developed to achieve automatic event classification.     

Low‐Fouling Electrosprayed Hemoglobin Nanoparticles with Antioxidant Protection as Promising Oxygen Carriers

Despite all the attempts to create advanced hemoglobin (Hb)‐based oxygen carriers (HBOCs) employing an encapsulation platform, major challenges including attaining a high Hb loading and long circulation times still need to be overcome. Herein, the fabrication, for the first time, of nanoparticles fully made of Hb (Hb‐NPs) employing the electrospray technique is reported. The Hb‐NPs are then coated by antioxidant and self‐polymerized poly(dopamine) (PDA) to minimize the conversion of Hb into nonfunctional methemoglobin (metHb). The PDA shell is further functionalized with poly(ethylene glycol) (PEG) to achieve stealth properties. The results demonstrate that the as‐prepared Hb‐NPs are hemo‐ and biocompatible while offering antioxidant protection and decreasing the formation of metHb. Additionally, decoration with PEG results in decreased protein adsorption onto the Hb‐NPs surface, suggesting a prolonged retention time within the body. Finally, the Hb‐NPs also preserve the reversible oxygen‐binding and releasing properties of Hb. All in all, within this study, a novel HBOCs with high Hb content is fabricated and its potential as an artificial blood substitute is evaluated.     

Facile synthesis of inorganic–organic Fe2W18Fe4@NiO@CTS hybrid nanocatalyst induced efficient performance in oxidative desulfurization of real fuel

In this work, a new nanocatalyst, Fe₂W₁₈Fe₄@NiO@CTS, was synthesized by the reaction of sandwich‐type polyoxometalate (Fe₂W₁₈Fe₄), nickel oxide (NiO), and chitosan (CTS) via sol–gel method. The assembled nanocatalyst was systematically characterized by FT‐IR, UV–vis, XRD, SEM, and EDX analysis. The catalytic activity of Fe₂W₁₈Fe₄@NiO@CTS was tested on oxidative desulfurization (ODS) of real gasoline and model fuels. The experimental results revealed that the levels of sulfur content and mercaptan compounds of gasoline were lowered with 97% efficiency. Also, the Fe₂W₁₈Fe₄@NiO@CTS nanocatalyst demonstrated an outstanding catalytic performance for the oxidation of dibenzothiophene (DBT) in the model fuel. The major factors that influence the desulfurization efficiency and the kinetic study of the ODS reactions were fully detailed and discussed. The probable ODS pathway was proposed via the electrophilic mechanism on the basis of the electrophilic characteristic of the metal‐oxo‐peroxo intermediates. The prepared nanocatalyst could be reused for 5 successive runs without any appreciable loss in its catalytic activity. As a result, the current study suggested the potential application of the Fe₂W₁₈Fe₄@NiO@CTS hybrid nanocatalyst as an ideal candidate for removal of sulfur compounds from fuel.     

Cu(II) immobilized on Fe3O4–diethylenetriamine: A new magnetically recoverable catalyst for the synthesis of 2,3‐dihydroquinazolin‐4(1H)‐ones and oxidative coupling of thiols

Cu(II) immobilized on Fe₃O₄–diethylenetriamine was designed as a new, inexpensive and efficient heterogeneous catalyst for the synthesis of 2,3‐dihydroquinazolin‐4(1H )‐ones and the oxidative coupling of thiols. The structure of the nanomagnetic catalyst was comprehensively characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, vibrating sample magnetometry, thermogravimetric analysis, X‐ray diffraction and atomic absorption spectroscopy. Simple preparation of the catalyst from commercially available materials, high catalytic activity, simple operation, high yields, use of green solvents, easy magnetic separation and reusability of the catalyst with unaltered activity make our protocol a green and feasible synthetic strategy.     

金属氧化物对十氯联苯的降解研究

分别以市售的Fe2O3、MgO和CaO为催化剂,对十氯联苯(CB209)进行了催化降解研究.结果表明,MgO对CB209的降解具有较高的活性.在反应温度为300℃,反应时间为60 min时,MgO对CB209的降解效率达到98.9%.进一步研究表明,MgO催化降解CB209的动力学符合准一级动力学反应.通过GC-MS和GC-ECD,并结合衍生化实验,检测到九氯联苯、五氯苯和四氯苯、五氯苯酚、四氯苯酚和三氯苯酚等降解产物,进而推测出MgO催化降解CB209的过程中存在相互竞争的反应路径:氧化反应、碳碳桥键断裂和加氢脱氯.     

Protective activity of an anthocyanin-rich extract from bilberries and blackcurrants on acute acetaminophen-induced hepatotoxicity in rats

Acetaminophen (N-acetyl-p-aminophenol, APAP) overdosage can produce fatal centrilobular hepatic necrosis in humans. The present study attempted to investigate the protective effect of an anthocyanin-rich extract from bilberries and blackcurrants (AE) against APAP-induced acute hepatic damage in rats. Treatment with AE normalised blood activities of glutamate oxaloacetate and glutamate pyruvate transaminase and prevented APAP-induced plasmatic and tissutal alterations in biomarkers of oxidative stress, probably due to various bioproperties of the components of the extract.     

Carbon-13 NMR Characterization of an O-Alkylated Derivative of the Theophylline Metabolite 1,3-Dimethyluric Acid

Abstract

The structure of the derivative formed during the reaction of 1,3-dimethyluric acid, the major metabolite of theophylline in humans, with iodopropane was elucidated. GC-MS analysis indicated the presence of a single dipropylated product even though three positional isomers are possible. The stability of the product was lower than anticipated since one of the alkyl groups added was readily removed by acid hydrolysis. Carbon-13 NMR proved to be the most useful technique for establishing the positions of alkylation. Assignment of carbon-13 resonances were consistent with placement of propyl groups on N-7 and on the oxygen at C-8. The structure of the product was assigned as 1,3-dimethyl-7-(1-propyl)-8-(1-propyloxy)xanthine. This O-alkylated structure is unusual since most heterocycles that can exist as lactim-lactam tautomers alkylate primarily on ring nitrogens.