Search Results (224)

A new bicyclic polyketide, amesilide (1), along with the previously reported metabolites, chamisides A (2), B (3), and E (4), chaetoconvosins B (5) and C (6), and chaetochromins A (7) and B (8), were isolated from the marine fungus Amesia nigricolor MUT6601. The structures of the compounds were determined by extensive spectrometric (HRMS) and spectroscopic (1D and 2D NMR) analyses, as well as specific rotation. Absolute configurations of the stereogenic centers of amesilide (1) were determined by a comparison of its experimental circular dichroism (CD) spectrum with its time-dependent density functional theory (TD-DFT) electronic circular dichroism (ECD) spectra. Among them, chaetochromins A (7) and B (8) showed strong antibacterial activity against Staphylococcus aureus S25 (MBC values of 12.50 µM and MIC values of 6.25 µM) and a moderate cytotoxicity against monocytes (THP-1) and peripheral blood cells (PBMC) (IC₅₀ values of 33.65–40.01 µM). Full article

Background: Transition metal complexes incorporating fluorinated counter anions represent a significant class of compounds with broad applications in industry, pharmaceuticals, and biomedicine. These fluorinated anions are known to enhance the solubility, stability, and reactivity of the complexes, thereby expanding their functional utility in various chemical and biological contexts. Methods: A set of metal(II) complexes of the general formula [MPy₆][B(C₆F₅)₄]₂ where (Py = pyridine, M = Mn (1), Fe (2), Co (3), Ni (4), Cu (5), Zn (6)) have been synthesized by direct reaction of metal halides and pyridine in the presence of Ag[B(C₆F₅)₄]. The complexes were characterized using different techniques to assure their purity, such as elemental analysis (EA), electron paramagnetic resonance (EPR) spectroscopy, thermogravimetric analysis (TGA), ultraviolet–visible (UV–Vis) spectroscopy, ¹¹B-NMR, ¹H-NMR, and FT-IR spectroscopy. The antimicrobial and antifungal properties against different types of bacteria and fungi were studied for all prepared complexes. Results: The synthesized complexes exhibited broad-spectrum antimicrobial activity, demonstrating variable efficacy compared to the reference antibiotic, oxytetracycline (positive control). Notably, complex 6 displayed exceptional antibacterial activity against Streptococcus pyogenes, with a minimum inhibitory concentration (MIC) of 4 µg/mL, outperforming the control (MIC = 8 µg/mL). Complexes 1, 2, and 4 showed promising activity against Shigella flexneri, Klebsiella pneumoniae, and Streptococcus pyogenes, each with MIC values of 8 µg/mL. Conversely, the lowest activity (MIC = 512 µg/mL) was observed for complexes 3, 5, and 6 against Pseudomonas aeruginosa, Escherichia coli, and Klebsiella pneumoniae, respectively. Regarding antifungal properties, complexes 5 and 6 demonstrated the highest activity against Candida albicans, with MIC values of 8 µg/mL, equivalent to that of the positive control, fluconazole. Density functional theory (DFT) calculations confirmed an overall octahedral coordination geometry for all complexes, with tetragonal distortions identified in complexes 3, 4, and 5. Full article

The in situ emulsification synergistic self-profile control system has wide application prospects for efficient development on offshore oil reservoirs. During water flooding in Bohai heavy oil reservoirs, random emulsification occurs with superimposed Jamin effects. Effectively utilizing this phenomenon can enhance the efficient development of offshore oilfields. This study addresses the challenges hindering water flooding development in offshore oilfields by investigating the emulsification mechanism and key influencing factors based on oil–water emulsion characteristics, thereby proposing a novel in situ emulsification flooding method. Based on a fundamental analysis of oil–water properties, key factors affecting emulsion stability were examined. Core flooding experiments clarified the impact of spontaneous oil–water emulsification on water flooding recovery. Two-dimensional T1–T2 NMR spectroscopy was employed to detect pure fluid components, innovating the method for distinguishing oil–water distribution during flooding and revealing the characteristics of in situ emulsification interactions. The results indicate that emulsions formed between crude oil and formation water under varying rheometer rotational speeds (500–2500 r/min), water cuts (30–80%), and emulsification temperatures (40–85 °C) are all water-in-oil (W/O) type. Emulsion viscosity exhibits a positive correlation with shear rate, with droplet sizes primarily ranging between 2 and 7 μm and a viscosity amplification factor up to 25.8. Emulsion stability deteriorates with increasing water cut and temperature. Prolonged shearing initially increases viscosity until stabilization. In low-permeability cores, spontaneous oil–water emulsification occurs, yielding a recovery factor of only 30%. For medium- and high-permeability cores (water cuts of 80% and 50%, respectively), recovery factors increased by 9.7% and 12%. The in situ generation of micron-scale emulsions in porous media achieved a recovery factor of approximately 50%, demonstrating significantly enhanced oil recovery (EOR) potential. During emulsification flooding, the system emulsifies oil at pore walls, intensifying water–wall interactions and stripping wall-adhered oil, leading to increased T2 signal intensity and reduced relaxation time. Oil–wall interactions and collision frequencies are lower than those of water, which appears in high-relaxation regions (T1/T2 > 5). The two-dimensional NMR spectrum clearly distinguishes oil and water distributions. Full article

In order to investigate bioactive natural products derived from the endophytic fungus Penicillium ochrochloron SWUKD4.1850, a comprehensive study focusing on secondary metabolites was conducted. This research led to the isolation of twenty distinct compounds, including a novel nortriterpenoid (compound 20), alongside nineteen compounds that had been previously characterized (compounds 1–19). The chemical structures of these compounds were elucidated using spectroscopic techniques and nuclear magnetic resonance (NMR) analyses. Compounds 1–17 were isolated for the first time as metabolites of P. ochrochloron. Except for compounds 1–14, significant structural similarity was discerned between the metabolites of the endophytic fungus and those of the host plant. Compound 20 is noted as the inaugural instance of a naturally occurring 27-nor-3,4-secocycloartane schinortriterpenoid, while compound 17 was identified in fungi for the first time. An antifungal assay showed that compound 10 displayed a broader antifungal spectrum and a stronger inhibitory effect towards four important plant pathogens, at inhibitory rates of 74.9 to 85.3%. The in vitro radical scavenging activities of compounds 1, 3, 8, 15, and 16 showed higher antioxidant activity than vitamin C. Moreover, a cytotoxic assay revealed that compound 20 had moderate cytotoxicity against the HL-60, SMMC-7721, and MCF-7 cell lines (IC₅₀ 6.5–17.8 μM). Collectively, these findings indicate that P. ochrochloron has abundant secondary metabolite synthesis ability in microbial metabolism and that these metabolites have good biological activity and have the potential to enhance plant disease resistance. Full article

The development and application of antimicrobial coatings has become increasingly important in both medical and industrial settings due to the rising threat of microbial contamination and antibiotic resistance. This paper focuses on the formulation, characterization, and investigation of coatings based on quaternized polysulfone, which are designed to encapsulate two broad-spectrum antimicrobial drugs with complementary activity, amphotericin B (AmB) and norfloxacin (NFX), with the primary aim of inhibiting pathogen colonization on surgical instruments. Structural characterization using FTIR, ¹H-NMR, and UV-Vis spectroscopy, along with supramolecular analysis via X-ray diffraction and polarized optical microscopy (POM), revealed strong physical interactions between the drugs and the quaternized polysulfone matrix. Scanning electron microscopy (SEM) confirmed a uniform distribution of the antimicrobial agents within the polymeric matrix. Surface wettability, assessed through water contact angle measurements, indicated moderate hydrophilicity (70–90°). The coatings also exhibited notable antioxidant activity, showing a 12-fold increase in DPPH radical inhibition compared to the control. Furthermore, all formulations demonstrated strong antimicrobial efficacy against three reference strains frequently associated with hospital-acquired infections, S. aureus, E. coli, and C. albicans, with inhibition zones ranging from 32 to 39.67 mm for bacterial strains and 13.86 to 20.86 mm for C. albicans. These data points indicate that these materials may be useful as antimicrobial coatings. Full article

The spatiotemporal heterogeneity of moisture distribution causes the coal pillar dams in underground water reservoirs to undergo long-term dry–wet cycles (DWCs) under varying moisture content increments (MCIs). Accurately measuring the pore damage and fractal dimensions (D_f) of coal rock by different MCIs under DWCs is a prerequisite for in-depth disclosure of the strength deterioration mechanism of underground reservoir coal pillar dams. This study employed low-field nuclear magnetic resonance (LF-NMR) to quantitatively characterize the pore structural evolution and fractal dimension with different MCI variations (Δw = 4%, 6%, 8%) after one to five DWCs. The results indicate that increasing MCIs at constant DWC numbers (N_DWC) induces significant increases in pore spectrum area, adsorption pore area, and seepage pore area. MRI visualization demonstrates a progressive migration of NMR signals from sample peripheries to internal regions, reflecting enhanced moisture infiltration with higher MCIs. Total porosity increases monotonically with MCIs across all tested cycles. Permeability, T₂ cutoff (T_2C), and D_f of free pores exhibit distinct response patterns. A porosity-based damage model further reveals that the promoting effect of cycle numbers on pore development and expansion outweighs that of MCIs at N_DWC = 5. This pore-scale analysis provides essential insights into the strength degradation mechanisms of coal pillar dams under hydro-mechanical coupling conditions. Full article

This study presents a methodology for developing a cyclodextrin-based delivery system for ceftobiprole, a poorly water-soluble and amphoteric drug, chemically stable in acidic conditions. Ceftobiprole is a broad-spectrum cephalosporin antibiotic administered clinically as its water-soluble prodrug, ceftobiprole medocaril, due to limited aqueous solubility of the parent compound. Solubility enhancement was achieved through complexation with anionic sulfobutylether-β-cyclodextrin (SBE-β-CD). At a pH below 3, ceftobiprole is protonated and cationic, which facilitates electrostatic interactions with the anionic cyclodextrin. An optimised high-performance liquid chromatography (HPLC) method was used to assess solubility, the impurity profile, and long-term chemical stability. X-ray powder diffraction (XRPD) confirmed the amorphous nature of the system and the absence of recrystallization. Nuclear magnetic resonance (NMR) and attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy supported the formation of a host–guest complex. The freeze-dried system prepared from 0.1 M formic acid solution contained negligible residual acid due to nearly complete sublimation. The most promising formulation was a ternary system of ceftobiprole, maleic acid, and SBE-β-CD (1:25:4 molar ratio), showing ~300-fold solubility improvement, low levels of degradation products, and stability after eight months at −20 °C. After pH adjustment to a parenterally acceptable level, the formulation demonstrated solubility and a pH comparable to the marketed drug product. Full article

Triazoles are important fragments in the development of fungicidal compounds. Fungi have gradually developed drug resistance against traditional fungicides due to long-term overuse. Therefore, there is an urgent need to discover new candidate compounds. A series of 1,2,4-triazole derivatives containing amino acid fragments were designed and synthesized based on mefentrifluconazole. All the target compounds were characterized by ¹H-NMR, ¹³C-NMR, and HRMS techniques. Their antifungal activities against five kinds of phytopathogenic fungi were evaluated in vitro. The results revealed that most compounds had broad-spectrum fungicidal activities at 50 μg/mL and four compounds exhibited better antifungal activity than the control drug mefentrifluconazole. Interestingly, the synthesized compounds 8d and 8k exhibited exceptional antifungal activity against Physalospora piricola, with EC₅₀ values of 10.808 µg/mL and 10.126 µg/mL, respectively. Molecular docking studies demonstrate that the 1,2,4-triazole derivatives 8d and 8k, which incorporate amino acid groups, exhibit strong binding affinity to 14α-demethylase (CYP51). These findings highlight the potential of these compounds as effective antifungal agents. Full article

Background/Objectives: Cannabis sativa has been utilized for medical purposes for thousands of years. It continues to be recognized as a plant with an extensive variety of medicinal and nutraceutical uses today. In this study, a chemical investigation of the flowers of C. sativa isolated by using a variety of chromatographic techniques led to the isolation of eleven compounds. These purified compounds were evaluated for antitumor activity against SK-N-SH neuroblastoma cells. Methods: The compounds were isolated by using chromatographic techniques. Their structures were identified by the examination of spectroscopic methods, including 1D (¹H, ¹³C, and DEPT) and 2D (COSY, HSQC, HMBC, and NOESY) nuclear magnetic resonance (NMR) spectra and mass spectrum, together with the comparison to those reported previously in the literature. The evaluation of toxicity on SK-N-SH cells was performed by the MTT method. Results: Eleven compounds were isolated from the flowers of C. sativa, including two new compounds, namely cannabielsoxa (1), 13²-hydroxypheophorbide c ethyl ester (2), and six known cannabinoids (6–11), together with the first isolation of chlorin-type compounds: pyropheophorbide A (3), 13²-hydroxypheophorbide b ethyl ester (4), and ligulariaphytin A (5) from this plant. The results also demonstrated that cannabinoid compounds had stronger inhibitory effects on neuroblastoma cells than chlorin-type compounds. Conclusions: The evaluation of the biological activities of compounds showed that compounds 4–10 could be considered as the potential compounds for antitumor effects against neuroblastomas. This is also highlighted by using docking analysis. Additionally, the results of this study also suggest that these compounds have the potential to be developed into antineuroblastoma products. Full article

Klebsiella oxytoca bacilli co-form the human intestinal microbiota, but in favorable conditions, they may also affect immunocompromised individuals, causing urinary tract infections, bacteremia, or antibiotic-associated hemorrhagic colitis. The growing numbers of clinical outbreaks of K. oxytoca infections make these bacteria an emerging pathogen, which is still masked by the predominant K. pneumoniae isolates. Thus, it is very important to advance knowledge on K. oxytoca pathogenicity. This work aims to characterize a urine isolate, K. oxytoca 0.062, from central Poland, which appears to present a multidrug-resistant and extended-spectrum β-lactamases-positive phenotype. The structural experiments include sugar and methylation analyses, mass spectrometry, and ¹H and ¹³C Nuclear Magnetic Resonance (NMR) spectroscopy. Additionally, ¹H,¹H ROESY, and ¹H,¹³C HMBC experiments were carried out on the high-molecular-weight O polysaccharide fraction of K. oxytoca lipopolysaccharides (LPSs). These analyses led to the detection of two polysaccharide antigens: one neutral, containing a linear trisaccharide unit called mannan, and one acidic, which is built up of a branched tetrasaccharide unit containing two mannopyranose (α-Manp) residues, one galactopyranose (β-Galp) residue, and one galacturonic acid (α-GalpA) residue. The GalpA residue seems to be a potential minor epitope, recognized by the selected Proteus antisera in the serological studies. Full article

In the present work, the epoxidation of fatty acid methyl esters (biodiesel or FAMEs) with an iodine number of 96.4 g/100 g and containing approximately 11% palmitic acid, 4% stearic acid, 51% oleic acid, 25% linoleic acid, and 5% linolenic acid was studied with an aqueous H₂O₂ solution and different quaternary phosphonium salts (QPSs) combined with the phosphotungstic heteropolyacid (HPA) H₃PW₁₂O₄₀ in a biphasic system. The effect of the molar ratio of H₂O₂:C=C on the epoxidation of FAMEs was investigated. The effect of the molar ratio of H₂O₂:C=C on the epoxy number (EN) and iodine number (IN) was measured. Multiple regression analysis methods were used to determine the regression model describing the influence of the various independent variables. In the results obtained, it was found that the highest yields were obtained for [P6][Phosf]. The optimum conditions for the epoxidation process with the systems used were a time range of 30 ± 4 min and a H₂O₂/double bond molar ratio in the range of 1.8 ± 0.2. The formation of epoxidised fatty acid methyl esters (E-FAMEs) was confirmed by FT-IR, ¹H NMR and ¹³C NMR analyses. In the FT-IR spectrum of the E-FAMEs, epoxy ring vibration signals were identified at 826 cm⁻¹. In the ¹H NMR spectrum, signals appeared in the range of 3.25–3.00 ppm, corresponding to epoxy ring formation in biodiesel, and in the range of 60–55 ppm in the ¹³C NMR spectrum. Full article

Sulfation of arabinogalactan (AG) from larch wood (Larix sibirica Ledeb.) in the melt of a sulfamic acid–urea mixture has been first examined. The impact of the AG sulfation temperature on the AG sulfate yield and the sulfur content has been established. The high sulfur content (11.3–11.6%) in sulfated AG has been obtained in the temperature range of 115–120 °C for a sulfation time of 0.5 h. The process effectively prevents molecular degradation under these conditions. The incorporation of sulfate groups into the arabinogalactan structure has been confirmed by the appearance of absorption bands in the FTIR spectrum that are typical of sulfate group vibrations. The ¹³C NMR spectroscopy study has proven that the AG sulfation in the melt of a sulfamic acid–urea mixture leads to the substitution of some free hydroxyl groups for C6, C4, and C2 carbon atoms of the AG β-D-galactopyranose units. The advantage of the proposed AG sulfation method is that the reaction occurs without solvent, and the reaction time is only 0.5 h. The kinetics of the thermal decomposition of the initial AG and sulfated AG samples have been studied. It has been found that the sulfated AG samples have a lower thermal resistance than the initial AG. The kinetic analysis has revealed a decrease in the activation energy of the thermal degradation of the sulfated samples as compared to the initial AG. Full article

Thiopyrimidines represent one of the most active classes of compounds, possessing a wide spectrum of biological activities. Herein, we report the synthesis of 2-(heptylthio)pyrimidine-4,6-diamine (HPDA) via S-alkylation. The structure of HPDA was elucidated using ¹H and ¹³C nuclear magnetic resonance (NMR), heteronuclear multiple bond correlation (HMBC), high resolution mass (HRMS), and infrared (IR) spectroscopies. Full article

Vacancy defect graphitic carbon nitride (g-C₃N₄) and conjugated polyimide (PI) polymer photocatalysts have become increasingly recognized as metal-free photocatalysts featuring an appropriate bandgap. The narrow absorption spectrum of visible light and the rapid recombination rate of the photoexcited charge carriers in PI polymers and g-C₃N₄ impede its photocatalytic performance. The presence of oxygen vacancies (OVs) in PI polymer photocatalysts, as well as nitrogen vacancies (NVs) and carbon vacancies (CVs) in g-C₃N₄, can significantly enhance the migration of photogenerated electrons. Adding vacancies to improve the electronic structure and band gap width can greatly enhance the photocatalytic efficiency of PI polymers and g-C₃N₄. Defect engineering is important for increasing the photocatalytic ability of PI-polymer and g-C₃N₄. There remains a notable absence of thorough review papers covering the synthesis, characterization, and applications of vacancy-rich PI-polymer and g-C₃N₄ in photocatalysis. This review paper examines the roles of OVs in PI-polymer, NVs, and CVs in g-C₃N₄ and thoroughly summarizes the preparation approaches employed before and after, as well as during polymerization. This review scrutinizes spectroscopic characterization techniques, such as EPR, XPS, PAS, XRD, FTIR, and NMR, for vacancy defect analysis. We also reviewed the role of vacancies, which include light absorption, photogenerated charge carrier separation, and transfer dynamics. This review could serve as a comprehensive understanding, a vacancy-engineered design framework, and a practical guide for synthesizing and characterizing. Full article

Background: Thieno[2,3-c]pyridines and their analogs are not well explored for their anticancer properties. Hence, our research aimed to establish the anticancer potential of thieno[2,3-c]pyridines through cell-based assays and in silico evaluations. Methods: Thieno[2,3-c]pyridine derivatives 6(a–k) were synthesized and characterized using FT-IR, ¹H-NMR, ¹³C-NMR, and HRMS. All the synthesized compounds were screened initially for their anticancer activity against MCF7 and T47D (breast cancer), HSC3 (head and neck cancer), and RKO (colorectal cancer) cell lines using MTT assay. Apoptosis and cell cycle analyses were conducted using Annexin V/propidium iodide (PI) double staining for apoptosis assessment and PI staining for cell cycle analysis to investigate the mechanisms underlying the reduced cell viability. In silico molecular docking was accomplished for the synthesized compounds against the Hsp90 and determined pharmacokinetics properties. Results: From the screening assay, compounds 6a and 6i were identified as potential inhibitors and were further subjected to IC₅₀ determination. The compound 6i showed potent inhibition against HSC3 (IC₅₀ = 10.8 µM), T47D (IC₅₀ = 11.7 µM), and RKO (IC₅₀ = 12.4 µM) cell lines, all of which indicated a broad spectrum of anticancer activity. Notably, 6i was found to induce G2 phase arrest, thereby inhibiting cell cycle progression. Molecular docking results indicated crucial molecular interactions of the synthesized ligands against the target Hsp90. Conclusion: The compound 6i induced cell death via mechanisms that are different from apoptosis. Thus, the synthesized thieno[2,3-c]pyridine derivatives can be suitable lead compounds to be optimized to obtain potent anticancer agents through Hsp90 inhibition. Full article