Search Results (6,759)

Chemical investigation of the marine sponge-derived Streptomyces xiamenensis 1310KO-148 afforded six polycyclic tetramate macrolactams (PTMs), including three known compounds (1–3) and three previously undescribed chlorohydrin-containing analogues, chlokamycins B–D (4–6). Their planar structures were elucidated by extensive analysis of 1D and 2D NMR spectra and HR-ESIMS data, while the relative configurations were assigned using NOESY correlations. The absolute configurations were further confirmed by electronic circular dichroism (ECD) calculations. Compounds 3–6 exhibited significant cytotoxic activity against 14 human cancer cell lines (GI₅₀ = 2.68–24.92 μM) and antibacterial activity against Staphylococcus aureus (MIC = 16.00–32.00 μg/mL) and Micrococcus luteus (MIC = 4.00–32.00 μg/mL) among six tested bacterial strains. Full article

In the context of the “dual-carbon” targets and the development of green building materials, lightweight mortar has attracted considerable attention, owing to its low density and excellent thermal insulation properties. However, lightweight aggregates, such as vitrified microspheres, while effectively reducing mortar density, exhibit high porosity and weak interfacial bonding, which compromise mechanical performance. To address this issue, this study introduces sugarcane bagasse fiber (SBF) as a reinforcing material, with contents of 0%, 0.4%, 0.8%, 1.2%, and 1.6%. The effects of SBF on physical properties (consistency, density, water absorption) and mechanical properties (compressive strength, flexural strength, and tensile bond strength) were systematically evaluated. Furthermore, low-field nuclear magnetic resonance (LF-NMR) and scanning electron microscopy (SEM) were employed to analyze pore structure and interfacial transition zone (ITZ) characteristics at multiple scales. The results indicate that: (1) at low contents (0.4–0.8%), SBF was uniformly dispersed, improving matrix compactness; (2) compared with the control group, the 28-day compressive, flexural, and tensile bond strengths increased by 7.1%, 13.1%, and 25%, respectively; (3) NMR analysis revealed that the incorporation of SBF significantly increased the proportion of capillary pores, reduced total porosity, and enhanced mortar compactness, thereby improving mechanical strength; (4) fractal dimension analysis showed that contents of 0.4% and 0.8% increased structural complexity while reducing pore connectivity, leading to higher compressive strength; (5) SEM observations further demonstrated that the fibers provided bridging and anchoring effects within the ITZ, promoted the deposition of hydration products, and enhanced interfacial compactness. Full article

Salophen-type Schiff base ligands derived from salicylaldehyde and naphthalene aldehydes were synthesized and coordinated to Ni(II) to obtain three nickel complexes (NiL1–NiL3), which were evaluated as heterogeneous electrocatalysts for the methanol electro-oxidation reaction (MOR) in alkaline media. The ligands and complexes were fully characterized by FT-IR, ¹H NMR, EPR, DART-MS, and elemental analysis, confirming tetradentate coordination through imine nitrogen and phenoxide oxygen donors. Electrochemical studies were carried out using carbon paste electrodes modified with 15 wt % of each complex. Cyclic voltammetry revealed that the electrocatalytic activity is mediated by the Ni(II)/Ni(III) redox couple, with Ni(III) oxohydroxide species acting as the active sites for methanol oxidation. Among the evaluated systems, NiL1@CPE showed superior performance at low methanol concentrations, while NiL2@CPE and NiL3@CPE exhibited higher current densities at elevated methanol concentrations. Scan-rate studies indicated that the oxidation process is diffusion-controlled, and a linear response to methanol concentration was observed over a wide concentration range. The results demonstrate that ligand structure and coordination geometry play a crucial role in modulating the electrocatalytic behavior of Ni(II) Schiff base complexes, highlighting their potential as cost-effective molecular catalysts for alkaline methanol oxidation. Full article

Bacterial and fungal infections, together with oxidative stress-mediated damage, remain major challenges in human health and in the protection of materials, highlighting the need for new multifunctional molecules that combine antioxidant and antimicrobial properties. In this context, a new chloropyridine-based derivative, N4,N4-bis((6-chloropyridin-3-yl)methyl)-N1,N1-diethylpentane-1,4-diamine (AMZ), was synthesized via a simple, catalyst-free N-alkylation of N1,N1-diethylpentane-1,4-diamine with 2-chloro-4-(chloromethyl)pyridine in acetonitrile at 55 °C, affording a 62% yield. The structure of AMZ was confirmed by melting point determination, ¹H and ¹³C NMR spectroscopy, and EI–MS analysis. Its antioxidant activity was evaluated using DPPH and FRAP assays with BHT as a reference standard, while antibacterial and antifungal activities were assessed via disk diffusion and microdilution methods to determine inhibition zones and MIC/MBC values. In silico investigations included drug-likeness and ADMET predictions, as well as molecular docking on catalase (PDB: 2CAG) and fungal CYP51 (PDB: 1EA1). AMZ exhibited dose-dependent radical scavenging in the DPPH assay, reaching 76.88 ± 3.20% inhibition at 1000 µg/mL, with an EC₅₀ of 26.03 ± 0.21 µg/mL, close to that of BHT (23.65 ± 0.22 µg/mL). In the FRAP assay, AMZ showed a higher reducing power than BHT at a low concentration (OD₅₀ µg/mL 0.177 ± 0.023 vs. 0.134 ± 0.017), although its FRAP EC₅₀ was higher (700.48 ± 22.54 vs. 400.16 ± 8.67 µg/mL). AMZ displayed broad-spectrum antimicrobial activity against Gram-positive and Gram-negative bacteria and fungi, with particularly strong effects on Bacillus subtilis (44.5 ± 0.5 mm; MIC/MBC 0.008 mg/mL) and Aspergillus niger (30 mm; MIC/MBC 0.030 mg/mL), in some cases comparable or superior to streptomycin and fluconazole. In silico analysis indicated that AMZ fulfilled major drug-likeness rules, showed high predicted intestinal absorption (91.14%), and was classified as non-AMES toxic, while docking predicted favorable binding to catalase and CYP51, in agreement with the experimental antioxidant and antifungal activities. These findings highlight the potential of AMZ as a multi-target pyridine-based lead compound that warrants further structural optimization and in vivo evaluation for applications in oxidative-stress-related and infectious conditions. Full article

Phaeodactylum tricornutum was cultivated in a 1000 L photobioreactors using f/2 medium. The resulting algal biomass contained 24.5% lipids, 37.8% protein, 19.4% carbohydrates, and had a gross energy content of 19.8 MJ/kg. These components were sequentially extracted. The ultra-high performance liquid chromatography-high resolution mass spectrometry (UHPLC-HRMS) analysis of lipids revealed 35 triacylglycerols, a wide range of galactolipids and phospholipids including a novel sulfoquinovosyl diacylglycerol (SQDG), namely SQDG(C16:1/C24:0), characterized by mass fragmentation analysis. Additionally, three sulfoquinovosyl monoacylglycerols (SQMGs) with C14:0, C16:0, and C16:1 fatty acyl chain were detected in P. tricornutum for the first time. Fatty acid analysis further confirmed that P. tricornutum is an excellent source of ecosapentaenoic acid, which is predominantly present in triacylglycerol and glycolipid forms. CombiFlash chromatography allowed for the separation of monogalactosyldiacylglycerols, digalactosyldicylglycerols, SQDGs and phosphatidycholines, and their structure were confirmed by NMR spectral analysis. Fucoxanthin was the major carotenoid, and the study showed all essential amino acids required for humans and fish were present in it. A two-phase in vitro gastric/pancreatic digestibility assay showed high protein digestibility for both whole biomass (89%) and protein isolate (77%). Monosaccharide analysis showed that polysaccharides extracted by EtOH precipitation after alkaline extraction and by hot water extraction contained similar monomers with different relative intensities. Protein isolates and polysaccharides exhibited antioxidant properties. Full article

Date palm (Phoenix dactylifera L.) by-products from bioethanol production represent an underutilized resource rich in bioactive molecules. This study aims to their valorization through characterization of polysaccharides and phenolic compounds from the Medjool variety, both before and after yeast fermentation for bioethanol production. Three sequential types of by-products were analyzed—Ext1 (post hot-extraction), Ext2 (post fermentation), and Ext3 (post distillation)—and compared with Dat-Me. High Performance Liquid Chromatograp-Diode Array Detector-Mass Spectrometry (HPLC-DAD-MS) analysis allowed identifying 22 phenolic compounds, primarily cinnamic acid derivatives and glycosylated flavones such as luteolin and chrysoeriol. Fermentation increased total phenolic content from dry weight, while leading to an improved polysaccharide recovery (i.e., from 14.2% to 42.1% dry weight). Two polysaccharide fractions (F1 and F2) were isolated and characterized by ¹H-NMR and Dynamic Light Scattering (DLS). F1 is a pectic polysaccharide, with a galacturonic acid content ranging from 24.2% (Ext3) to 52.2% (Dat-Me), a degree of methylation (DM) between 34.4 and 50.6%, and a degree of acetylation (DA) of 23.6–42.2%. F2 consists of a non-pectic polysaccharide, characterized by a low galacturonic acid content (5.6–6.8%) and a DM of 12.6–47.1%, but it is highly acetylated, with a DA ranging from 90.1 to 93.3%. DLS analysis confirmed fermentation-induced depolymerization, with molecular weights ranging from 6.6 × 10⁴ to 8.5 × 10⁵ KDa for both the fractions. Overall, Medjool date by-products obtained after bioethanol production represent a sustainable source of high-value phenolic antioxidants and polysaccharides with different structures suitable for future applications in food, pharmaceutical, and cosmetic formulations. Full article

To reveal the energy transfer mechanism of water injection and the dynamic response characteristics of pore pressure in tight sandstone reservoirs, and to clarify the influence of lithology, injection pressure, and injection method on the energy enhancement effect of water injection, a high-pressure energy injection and response testing system and nuclear magnetic resonance (NMR) testing technology were used to conduct systematic water injection energy enhancement experiments on three rock types: mudstone, sandstone, and naturally fractured sandstone. Combined with pressure dynamic monitoring and pore structure evolution analysis, the pressure response characteristics and energy enhancement mechanism of rock samples under different experimental conditions were explored. The experimental results showed that the NMR T₂ distribution of the three rock samples exhibited bimodal characteristics, corresponding to small pores (pore size < 1000 nm) and large pores/microcracks (pore size > 1000 nm), respectively. There were significant lithological differences in the evolution of pore structure during water injection, with a cumulative decrease of 7.2% in the proportion of large pores in mudstone and an increase of 9.3% in the proportion of large pores in sandstone with natural fracture development. There is a positive correlation between injection pressure and the energy enhancement effect. Under an injection pressure of 40 MPa, the pressure increment at the outlet end of sandstone with natural fracture development reaches 8.06 MPa, and the energy enhancement effect is 24% higher than that under the 30 MPa working condition, while the mudstone only increases by 15%. The energy enhancement effect of intermittent water injection is significantly better than that of depleted water injection, and the energy enhancement effects of the three rock samples are increased by 18.6%, 12.0%, and 6.9%, respectively. Overall, sandstone with natural fractures has the best energy enhancement effect, followed by sandstone, and mudstone has the worst. The connectivity of pores and the degree of fracture development are the core factors that dominate the water injection energy enhancement effect and pressure transmission efficiency. The research results can provide reliable experimental basis and theoretical support for optimizing water injection development plans, improving energy efficiency, and dynamically regulating stress fields in tight sandstone reservoirs. Full article

To address the critical challenge of drilling fluid invasion in deep coalbed methane (CBM) reservoirs, this study provides novel insight into the micro-scale sealing mechanism and pore structure evolution by leveraging Low-Field Nuclear Magnetic Resonance (LF-NMR) as a quantitative probe. Unlike traditional macroscopic evaluations, we utilized dynamic NMR T₂ spectral analysis to decipher the synergistic behavior of a proposed “Bridging–Filling–Densifying” ternary sealing system, which integrates a nano-plugging agent, micro-fillers, and size-matched skeletal agents. The results demonstrate a significant improvement in sealing efficiency. The optimized hierarchical architecture reduced the NMR signal intensity of the invaded cores by over 99.8% under a differential pressure of 10 MPa, effectively eliminating fluid invasion channels. Crucially, the study reveals that while multi-scale particle size matching is the precondition for sealing, the mechanical rigidity of the skeletal particles is the determinant for maintaining filter cake integrity against high-pressure deformation. These findings elucidate the transition from a “macropore-dominated” structure to a “zero-detectable” sealed state, establishing a robust theoretical framework for designing non-damaging drilling fluids tailored to the complex geomechanics of deep CBM exploration. Full article

A modular synthetic route has been developed to prepare a new series of cationic ruthenium(II) complexes with electron-withdrawing 1,2-diacylcyclopentadienyl ligands. The 2-acyl-6-hydroxyfulvenes were synthesized from cyclopentadienide and acyl chlorides and converted to Tl(I) cyclopentadienyl salts using Tl₂SO₄/KOH. Transmetalation with [Ru(η⁶-p-cymene)(μ-Cl)Cl]₂ followed by PF₆⁻ metathesis gives the complexes [Ru{η⁵-1,2-C₅H₃(CO–R)₂}(η⁶-p-cymene)][PF₆] (R = t-Bu, p-Tol, p-ClC₆H₄, p-IC₆H₄) in moderate to high yields. The new compounds were characterized by NMR and IR spectroscopy; mass spectrometry and elemental analysis were performed where applicable. X-ray analysis of one of the complexes confirms that electron-deficient Cp ligands retain η⁵-coordination and structural planarity within Ru(II)–arene sandwich architectures, highlighting their potential utility in electronically tunable organometallic frameworks. Full article

Three new cyclic tetrapeptides (nectriatidels A-C, 1–3), two new curvularin analogs (6 and 7), and four known compounds (4 and 5, 8 and 9) were isolated from the marine-derived fungal-bacterial symbiont Aspergillus spelaeus GXIMD 04541/Sphingomonas echinoides GXIMD 04532, which was obtained from Mauritia arabica in shallow coastal waters. Their structures were elucidated through NMR spectroscopy and HRESIMS, and their absolute configurations were determined by Marfey’s method and quantum chemical calculations. Compounds 1–5 showed moderate amphotericin B (AmB)-potentiating activity against Candida albicans. Compounds 7 and 8 exhibited significant activities against Mycobacterium tuberculosis, with MIC values of 32 and 16 μg/mL, respectively. Additionally, compounds 7 and 8 exhibited moderate cytotoxicity against human colorectal cancer cell lines DLD-1 and SW480, with IC₅₀ values of 25~36 μM. Whole-genome sequencing of A. spelaeus revealed a 35.91 Mb assembly encoding 106 biosynthetic gene clusters (BGCs). antiSMASH analysis revealed that 79 of these BGCs (74.5%) displayed no significant similarity to known pathways in the MIBiG database, which is dominated by hybrid clusters, terpene, T1PKS, NRPS, and NRPS-like types. Genomic analysis identified the putative biosynthetic gene clusters for these metabolites and confirmed the fungal host as the predominant producer. Full article

The genus Psiadia (Asteraceae), widely distributed in Madagascar and the Mascarene Islands (Mauritius, La Réunion, Rodrigues), is traditionally used to treat bronchitis, asthma, colds, abdominal pain, and other inflammatory disorders. However, few studies have scientifically validated these traditional medicinal uses. To assess P. dentata as a valuable source of bioactive natural products, a combined ¹H NMR-based metabolomic, molecular networking, and phytochemical study was conducted. Multivariate analysis (PLS-DA) of crude extracts from Psiadia species collected on Reunion Island enabled rapid discrimination of active extracts from P. dentata and revealed two methoxylated flavonoids and one coumarin as metabolites correlated with its antiplasmodial and anti-inflammatory activities. Additionally, UHPLC-DAD-ESI-QTOF-MS/MS molecular networking approach enabled detailed chemical profiling of this species, allowing the annotation of 25 compounds (1–25) in this species. Subsequent phytochemical investigation of P. dentata leaves led to the isolation and identification of 25 metabolites, including nine new diterpenes (26–34), one new coumarin (35), and 15 known compounds (1–8, 11, 18, 19 and 36–39) from the diterpenoid, flavonoid, and coumarin families. The structures of the new compounds were elucidated using spectroscopic methods, including extensive 1D and 2D NMR and HRESIMS analyses. Biological evaluation of the isolated compounds showed that compounds 1, 7, 26 and 27 showed antiplasmodial activity against Plasmodium falciparum (3D7 strain, IC₅₀ = 7.25–13.46 μM). Compounds 7, 26, 27, 31 and 32 inhibited nitric oxide production (IC₅₀ = 0.87–27.71 μM), indicating potential anti-inflammatory effects. Only compound 1 displayed moderate cytotoxicity against HepG2 and HT29 cancer cell lines (IC₅₀ = 25.67 and 18.35 μM, respectively). Full article

In this Short Note type article, we report the synthesis of a new hybrid molecule, N-(3,4-dimethoxyphenethyl)-2-propylpentanamide, using a solvent-minimized mechanochemical method that provides a simple and efficient synthetic approach. The process achieved high yield. The compound was confirmed by melting-point analysis, ¹H and ¹³C NMR, IR spectroscopy, and mass spectrometry. Full article

The preparation of the novel optically active sulfoxides (-)-(S)-1,1,1,3,3,3-hexafluoro-2-[o-(p-tolylsulfinyl)phenyl]propan-2-ol 1, (-)-(S)-1,1,1,3,3,3-hexafluoro-2-[o-(methylsulfinyl)phenyl]propan-2-ol 2 and (-)-(S)-1,1,1,3,3,3-hexafluoro-2-[o-(t-butyl-sulfinyl)phenyl]propan-2-ol 3 according to the Andersen methodology and their spectroscopic characterization is presented. The NMR and CD spectroscopic evidence of the existence of the equilibrium between sulfoxide and hypervalent sulfurane forms of these compounds in solution and attempts at the isolation of corresponding sulfuranes are shown. For compound 3, the unprecedented subsequent irreversible transformation in solution into corresponding cyclic sulfinate ester–sultine 17 was established on the basis of NMR spectroscopy measurements. The mechanism of this transformation was investigated by means of GC-MS analysis and confirmed on the basis of synthesized long alkyl chain analog 23 transformation in solution. Moreover, the oxidation properties of obtained sulfoxides 2 and 3 for the selected compounds are described. Full article

Metabolomic profiling of the leaves, floral buds, flowers, and fruits of Ternstroemia lineata was conducted across the dry and rainy seasons in Mexico. The presence of katsumadin was determined and its antibacterial activity was evaluated. Multivariate data analysis was performed using proton nuclear magnetic resonance (¹H NMR) and Principal Component Analysis (PCA). Katsumadin was identified by ¹H NMR and, quantified by HPLC, and its antibacterial activity was assessed using a microdilution assay. The results revealed conserved ¹H NMR signals among leaf, flower buds, flowers and fruits, as well as signals that were either organ-specific or time-dependent. The spatial and temporal distribution of katsumadin was monitored over a nine-month period. During the dry season, katsumadin reached 1.5 mg/g DW in the leaves, whereas it was not detected during the rainy season. Higher katsumadin contents were observed in floral buds, fruits, and flowers (6.09 ± 0.10, 3.0 ± 0.79, and 3.4 ± 0.42 mg/g DW, respectively). In addition, katsumadin was evaluated against Salmonella Typhi and Pseudomonas aeruginosa, exhibiting a minimum inhibitory concentration and bactericidal effect at 0.5 mg/mL. Full article

In our previous study, a taste sensor employing a lipid/polymer membrane modified with 2,6-dihydroxyterephthalic acid (2,6-DHTPA) enabled the detection of the umami substances monosodium glutamate (MSG) and inosinate monophosphate (IMP). The taste sensor was also able to evaluate the synergistic effect, an umami enhancement phenomenon that occurs between MSG and IMP. However, the structural requirements for modifiers capable of detecting IMP have not yet been clarified. In the present study, to elucidate these requirements, nine different modifiers were prepared, and taste sensor measurements for IMP were conducted in combination with ¹H-NMR analysis. As a result, three distinct patterns were observed: (1) modifiers that exhibited chemical shift changes and generated a potential response in the positive direction (i.e., a positive potential response); (2) modifiers that showed chemical shift changes but produced either an almost zero or a negative potential response; and (3) modifiers that exhibited neither chemical shift changes nor any potential response. For receptor membranes that did not exhibit a positive response, the corresponding modifiers either lacked two carboxyl groups or did not possess intramolecular hydrogen bonding involving hydroxyl groups. From these results, it was clarified that the essential conditions for obtaining a positive potential response to IMP are that the modifier (1) contains two carboxyl groups and (2) possesses intramolecular hydrogen bonding. Full article