Search Results (1,886)

Five new oligophenalenone dimers, talarostipins A–E (1–5), including four N-containing derivatives, together with sixteen known duclauxin analogues (6–21), were isolated from the soil fungus Talaromyces stipitatus, and their structures were identified by a combination of NMR spectroscopic analyses, HRESIMS and ECD spectra. Anti-neuroinflammatory activity evaluation indicated that duclauxamide C (8) significantly inhibited NO generation in lipopolysaccharide (LPS)-induced BV-2 microglial cells with an IC₅₀ value of 5.0 ± 0.7 μM. Transcriptome sequencing analysis indicated that 8 probably suppressed neuroinflammation by targeting the NF-κB signaling pathway. Further verification was conducted by Western blot analysis, which indicated that 8 exerted its anti-neuroinflammatory effect by downregulating the expression of pro-inflammatory proteins, including inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2) and p65. Full article

We report here a thorough study concerning the acylation reaction products of 8-hydroxyquinoline with 2-chloroacyl chloride, with new insights and clarifications in respect to the obtained products brought by NMR and X-ray studies. According to the reaction conditions we employed, three compounds could be obtained: 1-(2-chloro-2-oxoethyl)pyridin-1-ium chloride 10, 8-hydroxyquinoline hydrochloride 11, and the acylated product 8-(2-chloroacetoxy)quinolin-1-ium chloride 12. A certain influence of the catalyst and the used solvent was observed, and feasible explanations for product formations were furnished. The structure of the compounds was proved by using ¹H- and ¹³C-NMR spectra as well as single-crystal X-ray diffraction studies for compounds 12 and 11. According to X-ray crystallography, compounds 11 and 12 have a planar structure and exhibit an ionic crystal structure crystallized as a hydrochloride salt of the corresponding organic base. The crystal structures of both compounds are stabilized by intermolecular hydrogen bonds and π-π stacking interactions. In the crystals of compounds 11 and 12, the structural components are interconnected by a system of intermolecular hydrogen bonding, and a similar one-dimensional array is formed via hydrogen bonding and π-π stacking. The further assembling of the structure for 12 and 11 occurs with the formation of a three-dimensional supramolecular network. Full article

Lophatherum gracile Brongn. (L. gracile) has been utilized as a food or medicinal plant for a long time. A series of chemical and spectroscopic methods was used to characterize the extracted and purified L. gracile polysaccharide (LGP). Its in vivo antitumor activity in the H22 tumor-bearing mice model was studied. LGP has a molecular weight of 1.42 × 10⁶ Da and is mainly composed of arabinose (Ara), galactose (Gal), xylose (Xyl), and other monosaccharides. NMR spectra suggest that LGP may be composed of 1,3-β-Galp and 1,3,6-β-Galp main chains, and a side chain formed by a 1,5-α-Araf short chain. The termini are composed of T-α-Araf, while [→4) -α-GalpA-(1→2)-α-Rhap-(1→] are attached to the backbone as short side chains, and the other monosaccharides are an arabinogalactan composed of the termini. SEM and AFM revealed that LGP presents a lamellar morphology with smooth surfaces and notable molecular aggregation. The Congo red assay, CD spectroscopy, and XRD collectively indicated the absence of a triple helix conformation and an overall amorphous structure in LGP. Compared with the model group, LGP treatment improved body responses, immune organs, and SOD and MDA levels. The tumor cell apoptosis rate in the high-dose LGP group was 50.0%. In the distribution of the tumor cell cycle, the proportions of the S phase were 29.1% and 41.1% in the low-dose LGP and high-dose LGP groups, respectively, compared with 12.2% in the model group. These results suggest that LGP exhibits preliminary antitumor activity, indicating its potential as a candidate for further cancer research. Full article

1-Phenyl-4-p-tolyl-[1,2,3]triazole was obtained via a CuAAC reaction involving phenyl azide and 1-ethynyl-4-methylbenzene. The NMR spectra of the compound are discussed, and its crystal structure was studied by X-ray analysis. According to the latter analysis and a Hirshfeld surface analysis, the predominant intermolecular C-H⋅⋅⋅N and C-H⋅⋅⋅π interactions in this molecule are responsible for crystal packing. Full article

This study explored the feasibility of near-infrared (NIR) spectroscopy for detecting total water, free water and bound water in carrot slices during freeze-drying, with low-field nuclear magnetic resonance (LF-NMR) characterizing water state distribution and oven-drying determining moisture content (MC). NIR spectra (10,000–4000 cm⁻¹) were processed via optimized sample partitioning, preprocessing and feature extraction; partial least squares regression (PLSR), support vector regression (SVR), back-propagation artificial neural network (BPANN), extreme gradient boosting (XGBoost) and particle swarm optimization–random forest (PSO-RF) models were established and evaluated. Results showed that SVR and BPANN performed robustly, with CARS being the optimal feature extraction method. The full-moisture system achieved high total/free water prediction accuracy ($R_p^2$ = 0.9902/0.9740), while the low-moisture system improved bound water prediction ($R_p^2$ = 0.9709). The established NIR models exhibited excellent fitting and generalization ability, enabling rapid and non-destructive quantitative prediction of moisture content during carrot freeze-drying. Full article

This study reports the synthesis, spectroscopic characterization, and biological evaluation of a novel moxifloxacin hydrazide derivative (MOX-H) and its metal complexes with Co(II), Ni(II), Cu(II), VO(IV), and Gd(III). The ligand was synthesized by hydrazinolysis of moxifloxacin hydrochloride, and the resulting hydrazide was subsequently complexed with the respective metal salts. The interaction between MOX-H and the metal ions yielded the corresponding complexes, formulated as [Co(H₂O)Cl(MOX-H)₂]Cl·2.5H₂O, [Ni(H₂O)Cl(MOX-H)₂]Cl.4.5H₂O, [VO(MOX-H)₂]SO₄.3.5H₂O, [Gd (H₂O)(MOX-H)₂(NO₃)₂]NO₃.2H₂O, and [Cu(MOX-H)₂(H₂O)Cl]Cl·xH₂O (where x = 2, 2.5, 0.5, for products synthesized via template, microwave-assisted, and hydrothermal methods, respectively). The synthesized analogues were characterized by elemental analysis (CHN), FT-IR, UV-visible, and ¹H NMR spectroscopy, and mass spectrometry, as well as thermogravimetric (TG/DTG) and magnetic measurements. FT-IR spectra confirmed coordination through the hydrazide carbonyl and amine groups, while UV–visible and magnetic data indicated predominantly octahedral geometries. The thermal behavior exhibited multistep decomposition with activation parameters supporting exothermic processes. When compared to the free ligand, the metal complexes showed increased antimicrobial activity against both Gram-positive and Gram-negative bacteria and fungus species, particularly for the Co(II) and Cu(II) complexes, which showed the largest inhibition zones. The Cu(II)–MOX-H complex exhibited the lowest MIC values (4.88–9.76 µg/mL) among all tested compounds, confirming its outstanding antibacterial potency and high sensitivity compared to the free ligand and standard drug. Cytotoxicity assays demonstrated selective anticancer activity, with the Cu(II)–MOX-H complex showing the highest potency (IC₅₀ ≈ 2.95 µM against MCF-7 and IC₅₀ ≈ 0.98 µM against HepG-2), while maintaining minimal toxicity toward normal cells. These findings were corroborated by molecular docking investigations, which showed that the MOX-H complexes had substantial binding affinities (−9 to −10 kcal/mol) toward DNA topoisomerase II, consistent with their observed biological effects. Full article

The utilization and chemical transformation of carbon dioxide remains a pressing problem in modern chemistry. Numerous experimental and theoretical studies have focused on the interaction of CO₂ with amines. In this work, quantum chemical density functional theory (DFT) calculations of equilibrium geometries, energies, electronic and vibrational characteristics of CO₂-sensitive mono-, di-, tris-hydroxyamidines and their associates were carried out by the B3LYP/6-31G(d, p) method. The harmonic vibrational frequencies were scaled and compared with the experimental FTIR spectra for supporting wavenumber assignments. Natural bond orbital (NBO) analysis of the atomic charges and charge delocalization was employed to investigate the nature of hydrogen bonding in hydroxyamidine associates. We also used the intrinsically polarizable continuum model (IEFPCM), and the DFT-D3 method was applied to account for dispersion effects during associate formation. Using the 6-311+G(2d, p) basis set for tris-hydroxyamidine, and its adducts, a comparative analysis of the experimental and calculated ¹H NMR spectra was performed. Here, we considered non-trivial sites of carbon dioxide absorption and hydroxyamidine protonation, which, to our knowledge, have hardly been considered by other authors. Present DFT results agree rather well with the experimental data and support new insight into the formation of the PIL structure. Full article

Background/Objectives: Sea urchin gonads (“roe”) are a valuable seafood product and a chemically complex matrix whose composition varies with physiology and environment. We present a biphasic extraction and ¹H NMR workflow to build a reusable reference inventory of polar metabolites and apolar lipid features in Paracentrotus lividus. Methods: Gonads from 37 adults (23 males, 14 females) collected at two sites (Alicante and Jávea–Dénia, Spain; October 2024) were lyophilized, extracted with methanol/chloroform/water, and analyzed by 400 MHz ¹H NMR in buffered aqueous solution (polar) and CDCl₃ (apolar). Polar metabolite identification combined 1D patterns with database matching and ¹H–¹³C HSQC confirmation on representative samples, yielding 71 annotated resonances corresponding to 37 metabolites spanning amino acids, osmolytes/quaternary amines, carbohydrates/aminosugars, and nucleoside/purine-related compounds. Results: Polar fingerprints enabled supervised modelling: PLS-LDA separated sexes with low cross-validated error, and SPA/COSS ranking highlighted glycine, alanine, creatine and osmolyte-associated signals as key discriminants; pathway mapping supported the enrichment of amino-acid and one-carbon/purine networks. Apolar spectra were annotated at the motif level and used for lipid-index estimation, indicating substantial unsaturation but low docosahexaenoic acid (DHA) and modest sex effects. Conclusions: The curated peak lists and reporting framework facilitate reproducible NMR annotation and future comparative studies of P. lividus gonads. Full article

Prolonged water injection in unconsolidated sandstone reservoirs can induce pore rearrangement and modify flow pathways, thereby affecting reservoir performance. However, quantitative characterization of pore evolution in both temporal and spatial dimensions remains limited. This study investigates the mechanisms of pore-structure evolution during extended injection through a series of multi-scale experiments. Scanning electron microscopy and X-ray diffraction analyses were employed to compare mineral composition and microstructural characteristics before and after injection, while in situ nuclear magnetic resonance (NMR) monitoring captured the dynamic evolution process, enabling pore-size classification from T₂ spectra and fractal assessment of structural complexity. Segmented NMR measurements at different distances further resolved spatial heterogeneity. The results show that prolonged water injection reduced permeability by 10.4–32.1%, whereas porosity exhibited only minor variation, indicating that the decline in flow capacity is primarily controlled by pore–throat structural adjustment rather than pore volume loss. Mineralogical redistribution and fine-particle migration decreased the median pore radius by 21.5–51.8% and the micropore fractal dimension by 23.8–76.5%, with stronger responses observed at higher permeabilities, while meso- and macropore fractal dimensions remained nearly unchanged, indicating preferential modification of micropores with preservation of the main connected flow framework. Consistently, NMR responses reveal pronounced spatial heterogeneity along the flow direction. The NMR signal changes at the injection end were 11.2–18.4% and 7.7–21.7% during the early and intermediate stages, respectively, both exceeding those at the distal end (2.9–12.4% and 1.9–17.1%). These results indicate a downstream-attenuating structural modification gradient. The findings provide new insights into pore-structure evolution during prolonged water injection and offer a scientific basis for optimizing water-injection strategies in unconsolidated sandstone reservoirs. Full article

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

Nine new mycophenolic acid derivatives, penicacids O–W (1–9), two first-time reported natural products (10, 11), and five known compounds (12–16), were isolated from a marine-derived fungus Penicillium senticosum RCDB005 found in a South China Sea sediment sample. Their structures were determined using NMR, HRESIMS, and optical rotatory dispersion (ORD) spectra, electronic circular dichroism (ECD) calculations, X-ray crystallography, and modified Mosher’s methods. Eight of these compounds were evaluated for anti-proliferative effects against nine human cancer cell lines and the IC₅₀ values ranged from nM to μM levels. Compounds 5, 7–9 showed potent inhibition activity against MOLM-13 acute myeloid leukemia cells with IC₅₀ values between 0.13 and 1.13 μM. Full article

Tight sandstone reservoirs are characterized by highly heterogeneous pore structures, in which multiscale pore–throat systems jointly control the shapes of capillary pressure curves and relative permeability, thereby exerting a fundamental influence on water production behavior and the overall development performance of gas reservoirs. The Ordos Basin is generally characterized by the development of tight sandstone. The tight sandstones exhibit porosities of 2–13% and permeabilities of 0.01–10 × 10⁻³ μm². To quantitatively elucidate the controlling mechanisms of multiscale pore structure on capillary pressure curve morphology and relative permeability, this study systematically investigates the fractal and multifractal characteristics of pore structures in tight sandstones based on high-pressure mercury intrusion (MICP) and nuclear magnetic resonance (NMR) experimental data, and establishes a quantitative relationship between fractal parameters and the capillary pressure curve shape parameter λ. First, capillary pressure curves were fitted using the Brooks–Corey model within the effective saturation interval to extract the shape parameter λ, which characterizes the concentration degree of pore-size distribution and the drainage behavior. Subsequently, based on NMR T₂ spectra, the small-pore fractal dimension D₁, large-pore fractal dimension D₂, and the multifractal singularity spectrum width Δα were extracted to quantitatively describe the geometric complexity of pore structures at different scales. On this basis, the correlations between λ and D₁, D₂, and Δα were systematically analyzed, and the predictive performance of λ under different parameter combinations was compared. The results indicate that: (1) the pore structures of tight sandstones exhibit pronounced fractal and multifractal characteristics at the NMR T₂ scale, with significant differences among samples; (2) λ shows an overall negative correlation with fractal parameters, among which the correlations with the large-pore fractal dimension D₂ and the multifractal spectrum width Δα are the most significant; (3) compared with models using a single fractal dimension, the multiparameter model incorporating Δα provides a more comprehensive characterization of multiscale pore heterogeneity, leading to a substantial improvement in the accuracy and stability of λ prediction; and (4) λ exerts a clear control on the shape of relative permeability curves, where a larger λ corresponds to earlier initiation and forward-shifted rising segments of water-phase flow, while a smaller λ results in overall flatter relative permeability curves. From the perspectives of fractal and multifractal theory, this study establishes an intrinsic linkage among pore structure, capillary pressure curve shape parameters, and relative permeability, providing a novel quantitative framework for constraining relative permeability curve morphology in tight sandstones under conditions where systematic relative permeability experiments are unavailable. Full article

Reservoir quality in shallow lacustrine-mixed siliciclastic–carbonate systems is commonly governed by mineral assemblages and diagenetic modification. Here we investigate the Neogene Youshashan Formation (Oil Groups III–V) in the Nanyishan area, western Qaidam Basin, to quantify mineralogical and diagenetic controls on pore systems and flow. We integrate whole-rock XRD and log-derived mineral profiles with thin-section/SEM petrography, NMR T2 spectra, mercury injection capillary pressure (MICP), and a water-drop test. Dissolution-related pores and dolomitization-related intercrystalline pores dominate the pore space, whereas cementation and clay-related filling/coating locally restrict pore throats and connectivity. Algal limestones (average porosity 23.17% and permeability 54.3 mD; MICP r50 = 0.085 μm) show better reservoir quality than dolomitic rocks (average porosity 17.24% and permeability 15.13 mD; MICP r50 = 0.039 μm), consistent with more effective pore throat networks. In Oil Group III (Well NQ2-6-2), higher dolomite content is generally associated with higher porosity but shows no systematic relationship with permeability, highlighting the primacy of connected pore throats. Water-drop behaviors (beading, semi-beading, infiltration) provide a rapid, semi-quantitative screening indicator when interpreted together with pore throat metrics, and support a four-class reservoir-typing scheme (Types I–III and non-reservoir) for sweet-spot identification in mixed lacustrine reservoirs. Full article

Microalgae are rich in protein and phenolics, thereby having great potential for production of functional foods and nutraceuticals. However, despite featuring high nutritional value, these compounds often suffer from low stability and bioaccessibility. In this study, phenolics and protein extracted from Chlorella vulgaris were conjugated at different ratios (2.5–10%) and the structure and bioactivity of the conjugates were comprehensively characterized. The fluorescence intensity of protein decreased from 340 to 130–98 a.u. after conjugation and the UV-vis absorbance dropped from 1.6 to 0.5 a.u., which confirms the alteration of the chromophore area. The FTIR spectra revealed shifts in the C=O, N-H, and C-N bands, and the ¹H NMR spectra showed the broadening of signals and appearance of new peaks, indicating covalent bond formation through the Schiff base and Michael addition reactions. Conjugation significantly increased the antioxidant activities, in terms of ABTS inhibition by 644%, 257%, and 97%, as well as the ACE inhibitory activity, by 13.5%, 17.5%, and 19.7% for the 2.5%, 5% and 10% conjugates, respectively. The 2.5% conjugate showed the highest bioaccessibility (144%), which was 2.5 times that of free phenolics. Overall, this study proves that conjugation is an effective approach to enhancing the bioactivity and bioaccessibility of microalgae-derived compounds and unravel the structure–activity relationship of conjugates. The findings can promote the valorization of microalgae for product development in the food and nutraceutical industries. Full article

Quantifying the heterogeneity of pore-throat structure and evaluating reservoir quality are of great significance in the exploration and development of tight sandstone oil and gas reservoirs. This study focused on 10 samples of tight sandstone from the Benxi Formation in the Ordos Basin of China. Based on nuclear magnetic resonance (NMR) and combined with the theory of multifractal analysis to calculate multifractal parameters, the pore structure and fractal characteristics of tight sandstone reservoirs were characterized. The results showed that the dominant minerals are quartz, clay minerals, rock fragments and calcite, while feldspar content is relatively minor. The NMR T₂ spectra all exhibited bimodal characteristics. The pore size distribution of the reservoir has multifractal characteristics. The multifractal parameters D_min-D_max range from 2.02 to 2.88, D_min/D_max ranges from 3.69 to 5.11, and △α ranges from 2.441 to 3.316. Different mineral components had different effects on the fractal characteristics. The increase in quartz content retained more primary intergranular pores, affecting the fractal dimension of large pores, and weakening the heterogeneity of the pores. The increase in calcite and clay minerals corresponded to the enhancement of micropores and mesopores, increasing the heterogeneity of the pore structure. Based on the reservoir classification using multifractal parameters, the evolution of pore heterogeneity in tight sandstone rocks can be quantified, thereby effectively evaluating reservoir quality. Overall, reservoirs with larger D_min-D_max and D_min/D_max values, smaller △α, weaker porosity heterogeneity, and better connectivity are favorable areas for hydrocarbon exploration and development. The comprehensive fractal characterization of tight sandstone reservoirs demonstrates the applicability of multifractal dimensions in characterizing the heterogeneity of pore structures in tight sandstones, and is a key factor in improving the exploration effectiveness and development benefits of tight sandstone oil and gas reservoirs. Full article