We report, for the first time, the isolation of taraxerone from an isopropanol extract of chaya (Cnidoscolus aconitifolius), a traditional plant used in Mayan culture. Although this natural product has been previously identified in other plant species, the complete assignment of its NMR data had not been accomplished until now. To achieve this, we employed 2D NMR experiments to assign the H and C chemical shifts of taraxerone. Several approaches were used to determine the spin-spin coupling constants (J), including GIAO calculations, spin simulation, and dihedral angle analysis via a Karplus-type HLA equation. Conformational analysis revealed the presence of two conformations of Ring A: a chair and a twisted boat. To better understand the behavior of these conformers, a variable-temperature H NMR experiment was performed, in which Δδ/°C values for selected protons were monitored. These changes are attributed to stereoelectronic effects, such as the Perlin effect, as evidenced by J values obtained from HSQC nondecoupled experiments. Isotopomeric shifts (ΔC(H)) were also investigated. All findings were further supported by natural bond orbital (NBO) calculations, which helped explain the observed hyperconjugative interactions.

The structure, dynamics, and reaction kinetics exhibited by molecules in the solution state are essentially governed by their interactions with the solvents. Solvents influence solute structure, stability, aggregation, and binding through noncovalent solute-solvent interactions. Hence, understanding solute-solvent interactions is essential for elucidating the molecular behavior in solution. Traditionally, solute-solvent interactions are studied experimentally via solute properties, while theory examines both solute and solvent behavior. Nuclear magnetic resonance (NMR) spectroscopy offers a gamut of experimental methods for probing molecular interactions in condensed phase. Solvent-based NMR methods have become powerful tools to experimentally detect and quantify solute-solvent interactions. The present review highlights the solvent-detected as well as solvent-mediated NMR approaches discussed in literature in the past two decades portraying the dynamicity of solvents in shaping solute behavior-affecting structure, conformational flexibility, and intermolecular interactions. Solvents used in solution NMR experiments offer a plethora of NMR active nuclei both dipolar and quadrupolar in nature that can be efficiently probed to unveil molecular dynamics and interactions. NMR solvent-based methods, from simple to complex systems, are more efficient than other spectroscopic techniques. Solvent relaxation, magnetization transfer, and dynamic nuclear polarization effectively capture subtle solute-solvent interaction changes. These methods are reviewed in specifics to emphasize the potential of solvent-based NMR.

The H, C, N, and O chemical shifts of 91 nitro-1H-pyrazoles, as well as 1-amino-1H-pyrazole, were calculated using the Gauge-Invariant Atomic Orbital/Becke Three-parameter Lee-Yang-Parr [GIAO/B3LYP/6-311++G(d,p)] method. The majority of these compounds are polynitropyrazoles, including substituents such as N-nitro, C-nitro, and N-trinitromethyl groups. The calculated chemical shifts were compared with available experimental data using an empirical equation that relates absolute shieldings to chemical shifts. However, a new equation was required to accurately account for the oxygen atoms in the nitro groups. Additionally, some conformational studies were performed to better understand the chemical shifts, particularly those of the OH and NO substituents at position 1. Different statistical methods were used to analyze the calculated N chemical shifts.

These studies are intended to be a step towards the identification of characteristic markers of relaxation processes in tissues, with the aim of revealing the extent to which they are tissue and/or cancer specific, and thus to consider the potential of NMR relaxometry for diagnostic purposes. H spin-lattice and spin-spin relaxation studies were carried out on 20 samples of endometrial cancer tissue. The spin-lattice relaxation experiments were performed in the frequency range from 10 kHz to 10 MHz and complemented by spin-lattice and spin-spin relaxation measurements at 18.7 MHz. It was shown that the spin-lattice relaxation data can be reproduced in the form of a power-law function with the exponent of about 0.35 over the whole frequency range, while the spin-spin relaxation process was found to be bi-exponential in all cases. The relaxation scenario has been described quantitatively, leading to a number of parameters such as the ratio between the spin-spin relaxation rates and their contributions to the total relaxation process, or the relative decay of the spin-lattice relaxation rates in the low frequency range (from 10 to 100 kHz). As a result of H spin-lattice and spin-spin relaxation studies several characteristic relaxation features of endometrial cancer tissue have been revealed. The relaxation markers include the characteristic values of the relaxation rates, the shapes of the frequency dependencies of the spin-lattice relaxation rates and bi-exponentiality of the relaxation processes. The relaxation features have been compared with those for proteins and polymers.

CO flooding is commonly employed for enhanced oil recovery in tight reservoirs. However, asphaltene deposition-induced pore blockage occurs during injection. Conventional studies primarily neglect pore-scale impairment mechanisms. To accurately characterize asphaltene precipitation patterns and quantify microscopic pore blockage, this study integrates static miscibility experiments with dynamic flooding tests. The methodology investigates parametric influences on asphaltene precipitation volumes, evaluates deposition dynamics across pore-size distributions, and employs NMR to quantify pore blockage ratios. Experimental results demonstrated that the Chang-8 Block crude oil in the Ordos Basin exhibited a minimum miscibility pressure (MMP) of 18.58 MPa at 60°C, with the system being identified as asphaltene-unstable. Post-CO miscibility, asphaltene precipitation increases progressively with both rising temperature and pressure, reaching maximum escalation rates at pressures approaching the MMP. However, this escalation rate moderated when pressure exceeded the MMP. Formation damage and pore blockage ratios increased progressively with CO injection volumes, reaching 14.27% at 6 PV. Initial blockage occurred preferentially in macropores, followed by concurrent impairment in both macropores and micropores. Elevated displacement temperatures enhanced CO dissolution. Below CO critical conditions (T > 31.6°C, p > 7.38 MPa), limited displacement efficiency resulted in macropore blockage. Upon exceeding the critical temperature, pore blockage escalation intensified, achieving 25.22% at 60°C. This study systematically investigates asphaltene precipitation characteristics within tight reservoir cores during CO flooding, clarifies the precipitation law of asphaltene in the core under the influence of different factors, and provides operational guidelines for enhancing recovery efficiency and optimizing field-scale CO injection strategies in tight reservoirs.

Coumarin and benzimidazole are widely preferred pharmacophores in drug design due to their broad spectrum of biological activities, and hybrid molecules formed by the combination of these two structures are thought to possess improved pharmacokinetic and pharmacodynamic properties. In this study, four coumarin-substituted benzimidazolium salts were synthesized, three of which are reported here for the first time. Structural characterization was performed using NMR spectroscopy, FTIR, and elemental analysis. To assess their acid-base properties, the pK values of all compounds were determined using three complementary approaches: a signal intensity-based NMR method (pK), classical potentiometric titration (pK), and the ERETIC2-assisted quantitative NMR method (pK), which is applied for the first time in the literature for this purpose. Comparison of the obtained pK values showed that the pK method yielded values in the range of 10.7-11.4, the pK method provided values between 10.0 and 11.2, and the pK method resulted in values ranging from 12.1 to 12.8. All compounds displayed intermediate acidity, attributed to the formation of resonance-stabilized anionic species upon deprotonation by tetrabutylammonium hydroxide. The consistency between the acidity rankings obtained by ERETIC2 and potentiometric titration highlights the robustness of combining advanced NMR-based quantification with classical techniques for reliable and comparative pK determination.

NMR spectroscopy has been widely used for the identification and structural elucidation of key components found in essential oils. For many years, the combination of NMR spectroscopy with other analytical techniques, such as gas chromatography (GC) and mass spectrometry (MS), has allowed researchers to identify and quantify a wide variety of terpenes, terpenoids, aldehydes, and other very low-level components present in various essential oils. Importantly, however, whereas GC continues to be the most widely used technique for the quantification of these components, NMR spectroscopy is still mostly reserved for structural elucidation purposes. In this work, we demonstrate how benchtop NMR spectroscopy can also be used for the quantification of key species in various essential oils, increasing accessibility to this technique by decreasing the costs associated with traditional high-field NMR instrumentation and lowering the expertise barriers required for accessing this technique.

Two new sesquiterpenoids, neopinguisane-2β,5β-diol (1) (pinguisane-type) and isoseiricardine B (2) (seiricardine-type), along with two known compounds, pentalenic acid (3) and nakienone C (4), were isolated from the culture broth of Streptomyces argenteolus derived from Pantholops hodgsoni feces. Structures of new compounds 1 and 2 were elucidated through comprehensive analysis of 1D and 2D NMR spectroscopic data. The stereochemistry at C-10 of compound 2 could not be determined due to insufficient sample quantity. This study represents the first reported isolation of both pinguisane-type and seiricardine-type sesquiterpenoids from Streptomyces species. In addition, the antimicrobial activities of all isolated compounds were evaluated.

The series of new 2-substituted-5,7-di(het)aryl-6-nitro-4,5,6,7-tetrahydroazolo[1,5-a]pyrimidines were synthesized by reaction between imine and 1-substituted 2-nitroethylene derivatives. The structure of the obtained compounds including stereochemical configuration was confirmed by NMR techniques such as H, C, 2D H-H (gNOESY), H-C (gHSQC, gHMBC) 2D H-N gHMBC and XRD method, additionally. For the obtained compounds, the signals of all hydrogen, carbon, and nitrogen nuclei in the NMR spectra were associated using two-dimensional NMR experiments. Based on the analysis of the spin-spin coupling constants (SSCC), it was found that the target compounds were obtained in the form of trans-trans isomers.

A rapid, reagent-free method for the quantification of chitosan in aqueous solutions was developed using H nuclear magnetic resonance (NMR) relaxometry. Transverse relaxation times (T) of chitosan solutions (5-1000 mg/L) were measured with a Carr-Purcell-Meiboom-Gill (CPMG) sequence on a benchtop NMR relaxometer. The data were processed using three approaches: monoexponential fitting (Bruker software), inverse Laplace transformation (CONTIN), and one-component curve fitting (Excel Solver). Calibration curves derived from these models demonstrated high linearity and reproducibility, particularly when concentration intervals were segmented. Among the approaches, the most robust correlation was achieved by plotting the absolute area (AA) of the T distribution obtained from CONTIN analysis versus chitosan concentration, yielding R values of up to 0.9978 for 5-100 mg/L. Comparative analysis at 40°C and 21°C confirmed the method's temperature stability, with improved sensitivity at elevated temperature. Unlike conventional spectrophotometric or chromatographic methods, the proposed protocol requires no chemical derivatization or complex sample preparation. This technique provides a fast, accurate, and non-destructive alternative for chitosan quantification, especially suitable for material science applications where precise concentration monitoring is critical, such as surface modification of nanomaterials.

Spinocerebellar ataxia 12 (SCA12) is a progressive degenerative neurological disorder, primarily characterized by impaired coordination and balance. To investigate the correlation between proton (H) magnetic resonance spectroscopy (MRS) and structural imaging indices in patients with SCA12. T1-weighted MRI, DTI, and single voxel MRS point resolved spectroscopy (PRESS) in the left hemispheric cerebellum were acquired using a 3-T MR scanner in 40 SCA12 patients and 25 healthy controls. Correlations between metabolites, gray and white matter volume of lobules, fractional anisotropy (FA), and clinical, nonclinical, and genetic data were examined. Three machine learning algorithms (KNN, LDA, and SVM) were used to analyze the metabolic feature differences between SCA12 and HC groups. Significant decreases in choline (Cho [GPC (glycerophosphocholine) + PCh (phosphocholine)]) and N-acetyl aspartate (NAA) levels, along with increases in myo-inositol ratios to creatine, FA, and white matter volume values (p < 0.05), were observed in the cerebellum of the SCA12 group compared to healthy controls. Positive correlations were observed between NAA levels and cerebellar lobule volume, the SPM IQ score with the right crus II in the SCA12 group. The International Cooperative Ataxia Rating Scale (ICARS) score showed a negative correlation with white matter and specific cerebellar lobules. Disease duration and cytosine, adenine, and guanine (CAG) repeat length were negatively correlated with right lobule VIIIB, lobule IX, and left lobule X. Machine learning algorithms achieved an accuracy of over 95% in MRS data, and 88.89% in volumetric data. MRS, VBM, and DTI techniques reveal neuronal degeneration in SCA12 compared to healthy individuals.

The molecular dynamics of ionic liquids (ILs) can be probed using fast field cycling (FFC) NMR relaxometry. Conventionally, such studies focus on ILs where only one ionic species carries NMR-active nuclei or on systems combining H nuclei on the cations with F nuclei on the anions. This way, the dynamics of cations and anions can be resolved individually. However, the situation becomes considerably more complex in fully protonated systems where both ions contain protons, because the various relaxation pathways can no longer be disentangled. Here we report the first FFC NMR investigation of such a case, using the IL triethylammonium methanesulfonate ([TEA][OMs]). Our strategy exploits selective partial deuteration of the ionic species, which enables the separate evaluation of cation and anion dynamics. We demonstrate for the first time that, from the known partial relaxation rates together with the determined interionic distances and self-diffusion coefficients, the relaxation contribution arising from cation-anion interactions can be quantified. Remarkably, this approach even allows reconstruction of the total relaxation rate observed experimentally for the fully protonated IL. This methodology provides a fundamentally new route to overcoming the limited spectral resolution of FFC NMR relaxometry at low fields. More broadly, it establishes a framework for disentangling relaxation processes in complex multicomponent systems, thereby extending the applicability of FFC NMR to more challenging classes of ILs and related materials.

The spin Hamiltonian parameters (SHPs) (g factors g and g and hyperfine structure constants A and A) and their concentration (x) dependences for Cu in xNaI·(30-x)·NaO·70BO (5 ≤ x ≤ 25) glasses are theoretically investigated in a consistent way. The [CuO] complexes are subject to the Jahn-Teller effect, leading to the relative elongations of about 7%. The concentration dependences of the SHPs are suitably attributed to the nonmonotonic piecewise relationships of cubic field parameter, covalency factor, relative tetragonal elongation ratio, and core polarization constant with NaI concentration x due to the modifications of local crystal fields and electron cloud distribution around impurity Cu. The calculated cubic field splittings E, g factors, and A at various concentrations x agree well with the measured results, and the values of corresponding A are also predicted. The properties of optical and EPR spectra are discussed, and the microscopic mechanisms of the concentration dependences of the related quantities are also analyzed.

Compositions containing bitumen emulsions and solids have many applications, such as soil stabilization, cold mix asphalt preparation, dust binding, surface dressing and slurry sealing. Therefore, the interaction of bitumen with minerals is of great interest in science and applications. In the interaction of bitumen emulsion with a mineral surface, one of the processes that influence the properties of the bitumen-mineral composition is the formation of interface layers. Nuclear magnetic resonance can provide insights into the interactions of bitumen and minerals at the molecular level. However, the presence of magnetic constituents in most solids as well as the background magnetic field gradients at the interface does not allow the use of NMR to its full potential. In this work, we describe a H NMR approach to study the interface layer formed by a specified bitumen emulsion in the presence of non-magnetic as well as magnetic minerals. This approach is based on the consecutive flushing off of "bulky" components of the bitumen emulsion and the following extraction of the surface layer material, which can then be analyzed by NMR spectroscopy. As a proof of concept, this technique was tested on samples prepared using a bitumen emulsion and four different silicate minerals. The H NMR study showed that interfacial layers may accumulate asphaltenes adsorbed to mineral surfaces to a different extent depending on the specific elemental composition of minerals. More asphaltenes were detected in the interfacial layers on surfaces of studied minerals with a higher content of calcium.

The hydroethanolic extract obtained from the seeds of Annona diversifolia Saff (Annonaceae) fruits was analyzed to obtain a new cycloheptapeptide, called papaucin (1) or cyclo(-Pro-Val-Ile-Thr-Asn-Leu-Gly-). Its molecular structure was determined using 1D and 2D NMR spectroscopic techniques (H, C, HSQC, COSY, HMBC, and TOCSY) and MALDI-TOF mass spectrometry. Additionally, the antiprotozoal activity was evaluated. Papaucin (1) showed moderate positive activity compared with in vitro assays of Entamoeba histolytica and Giardia lamblia, with IC values of 63.07 and 67.62 μg mL respectively. On the other hand, in silico studies revealed a higher affinity of papaucin for the PFOR enzyme compared with metronidazole, as evidenced by a greater number of polar interactions. Regarding the ALR enzyme, papaucin also showed affinity, although at a binding site different from the main catalytic site. These results suggest that papaucin could exert its antiprotozoal effect through multiple mechanisms.

A chemical investigation of the 95% EtOH extract of Dendrobium nobile Lindl. led to the isolation of one new sesquiterpene component (1), together with one known compound (2). Its structure was completely and unambiguously assigned by 1D and 2D NMR spectra (H NMR, C NMR, HSQC, HMBC, COSY, and NOESY), and HR-ESI-MS spectroscopic analysis and the absolute configuration was confirmed by ECD calculation.

Osteoarthritis (OA) is a highly common chronic disease that decreases functional capacity and can cause disability. The early detection of the disease could help to develop treatments that may reduce the progression if not cure the disease. Proteoglycan depletion is known to occur at an early state of OA and the delayed gadolinium-enhanced magnetic resonance imaging (MRI) of cartilage (dGEMRIC) is currently considered as one of the most accurate methods for analyzing the depletion in articular cartilage (AC) despite the toxicity-related issues with gadolinium contrast agents. The aim of this study was to investigate the usability of amorphous manganese oxide (MnOx) for assessing the proteoglycan content in AC. The relaxation times of MnOx were determined at various fields and compared with the effect of gadolinium-diethylene triamine pentaacetic acid (Gd-DTPA) at 7.1 T. The diffusion of MnOx and Gd-DTPA into AC was analyzed ex vivo and followed for 24 h. Cartilage degeneration was evaluated with two histological scoring systems (OARSI and Mankin) to assess the relationship between OA severity and MnOx concentration. Relaxivity of MnOx was high and diffusion to the AC was faster than that of Gd-DTPA at 7.1 T. Using MnOx, T followed histological optical density (OD) of stained proteoglycans and correspondingly the concentration profiles followed in reverse the OD profiles in each human sample in a similar manner to Gd-DTPA in dGEMRIC. This pilot study showed some preliminary superiority in relaxation and diffusion into AC of MnOx in relation to Gd-DTPA.

NMR spectroscopy under magic angle spinning (MAS) conditions can be employed to study the freezing of aqueous solutions and gel-like systems without the need for specialized equipment. This is attractive as one sample can be studied in its liquid and solid form without changing the experimental setup. There are multiple areas that benefit from such an analysis. Here, we will thoroughly study the freezing process of various aqueous systems containing multiple NMR-active nuclei (H, B, C, Na, and Br) to gain detailed insights into what the prerequisites are, what problems one must be aware of and what limitations arise, how reproducible the measurements are, and what additional information can be gained from them for different sample types. As a further aspect it will be shown how the described setup can be used for the study of aqueous systems in solution at subfreezing conditions.

The local structures and the electron paramagnetic resonance (EPR) g factors of Cu centers in GdBaCuO and LaGdBaCuO are theoretically studied by using the perturbation formulas of the g factors for an orthorhombically elongated octahedral 3d cluster. In these formulas, the crystal-field parameters (CFPs) are determined from the superposition model and the local distortions due to the Jahn-Teller (JT) effect. Based on the calculations, the Cu-O bond lengths are found to experience the axial elongations δz (≈0.052 and 0.055 Å) along the c-axis and the planar bond length variations δr (≈0.061 and 0.128 Å) in the perpendicular (ab) plane for the orthorhombic Cu centers in GdBaCuO and LaGdBaCuO, respectively. The calculated g factors are in good agreement with the experimental data. The local structures of both Cu centers are discussed.

Peptide-based supramolecular hydrogels are well known for their biocompatibility and the various range of applications in biotechnologies. The grafting of nucleobases along with the multicomponent approach allows a fine tuning of the hydrogel properties to match new uses. Such adjustments rely on a precise understanding of the material at the atomic level, and nuclear magnetic resonance (NMR) spectroscopy is a tool of choice for soft matter study. High-resolution NMR and fast-field cycling NMR relaxation can be used to investigate the hydrogel gelation process through the study of the gelator signal and the water dynamical behavior along the gelation time. NMR dispersion profiles can also bring insights into the presence of different water pools and their mobility inside the hydrogel matrix by modeling dispersion curves and extracting correlation times. Measurements were performed at two different temperatures, 295 K and 313 K. Examining the effect of temperature provides insight into the mechanism underlying the transition from solution to gel. This approach highlights not only how an increase in temperature influences the gelation process but also how it affects solvent dynamics within the gelator structure.

For the structure elucidation of biflavones in which the subunits are linked by an ether bridge, two NMR spectroscopic approaches are shown to determine the position of the ether bridge, without derivatization of the compound. We show that the structures of the biflavones loniflavone and methylloniflavone, isolated from the leaves of Lonicera japonica Thunb. (Caprifoliaceae), have to be revised to ochnaflavone and methylochnaflavone, respectively.