2D NMR Research Articles

Sulfated Aeruginosins from Lake Kinneret: Microcystis Bloom, Isolation, Structure Elucidation, and Biological Activity.

Aeruginosins are common metabolites of cyanobacteria. In the course of re-isolation of the known aeruginosins KT608A and KT608B for bioassay studies, we isolated three new sulfated aeruginosins, named aeruginosins KT688 (1), KT718 (2), and KT575 (3), from the extract of a Microcystis cell mass collected during the 2016 spring bloom event in Lake Kinneret, Israel. The structures of the new compounds were established on the basis of analyses of the 1D and 2D NMR, as well as HRESIMS data. Marfey's method, coupled with HR ESI LCMS and chiral HPLC, was used to establish the absolute configuration of the amino acid and hydroxyphenyl lactic acid residues, respectively. Compounds 1-3 were tested for inhibition of the serine protease trypsin, and compounds 1 and 2 were found to exhibit IC50 values of 2.38 and 1.43 µM, respectively.

Stereoselective Oxidation of α-Copaene, a Fire Ant Repellent Sesquiterpene from the Essential Oil of Dipterocarpus turbinatus.

Imported fire ants are significant agricultural pests. Repellents can be used to prevent foraging fire ants from entering sensitive areas, including electrical equipment, nursing homes, and hospitals. Bioassay-guided fractionation of the essential oil extracted from gurjun balsam (Dipterocarpus turbinatus) resulted in the identification of (-)-α-copaene (1) as the repellent constituent with a minimum repellent effective dose (MRED) of 15.6 μg/g against both red imported fire ants (Solenopsis invicta) and hybrid imported fire ants (Solenopsis invicta × Solenopsis richteri). Stereoselective oxidation of 1 via autoxidation and chemical methods produced (-)-5R-hydroperoxy-α-copaene (2), (+)-3S-hydroperoxycopa-4-ene (3), (-)-α-copaene oxide (4), (+)-β-copaen-4α-ol (5), copaenediol (6), and copaene ketol (7). Reduction of 2 and 3 with triphenylphosphine afforded (-)-5R-hydroxy-α-copaene (2a) and (+)-3S-hydroxycopa-4-ene (3a), respectively, which led to the structural revision of copa-3-en-2α-ol and copa-2-en-4-ol as 2a and 3, respectively. The configurational assignment of compound 4 in the literature was also clarified by the detailed analysis of 2D NMR spectroscopic data. Compounds 2-7 showed repellency with MREDs ranging from 3.9 to 15.6 μg/g against hybrid and red imported fire ants, indicating that chemical modification can enhance the repellent effect of (-)-α-copaene.

Urea-lactic acid as efficient lignin solvent and its practical utility in sustainable electrospinning

The development of lignin-based materials presents a promising avenue for advancing green chemistry and mitigating environmental impact. However, the key challenge lies in the processability of lignin, which significantly affects its practical applications. Addressing the issues related to lignin's complex structure, variability, and reactivity is crucial for optimizing its incorporation into high-performance materials. Therefore, in this study we explore the efficacy of a urea-lactic acid-based deep eutectic solvent (ULA) for the dissolution of kraft lignin, aiming to enhance its practical utility in sustainable electrospinning processes, for the first time. Results of elemental analysis, IR and 2D NMR spectroscopy, provide crucial insights into the structural properties of the regenerated material post-DES treatment. The findings confirm a high lignin recovery rate, reaching up to 96.6 % for samples dissolved at 100°C. Additionally, 2D NMR analysis indicates that the process leads to partial esterification of lignin with lactate ions. The ability of the studied DES to effectively solubilize lignin underscores its potential as an efficient lignin solvent and facilitates the fabrication of lignin-based nanofibers via electrospinning. The incorporation of this DES in electrospinning processes promises significant advancements in the development of sustainable, lignin-derived materials and offers a green alternative for production of high-performance nanofibers. Preliminary results of electrochemical impedance spectroscopy and galvanostatic charge/discharge measurements confirm that the EDLC with prepared hydrogel electrolyte demonstrates attractive electrochemical properties (specific capacitance, CSP = 95 F g–1; series resistance RS = 2.2 Ω; charge transfer resistance, RCT = 1.6 Ω), which are comparable with the reference cell based on a commercial glass fibre separator. Hence, the DES-assisted-electrospinned lignin membrane can be viewed as a potential gel electrolyte matrix for practical use in construction of sustainable energy storage devices.

Asperinsuterpenes A-C from the Fungus Aspergillus insuetus BTBU20220155.

Three new meroterpenoids, asperinsuterpenes A-C (1-3), and eight previously reported natural products, namely asnovolin I (4), (2'E,4'E,6'E)-6-(1'-carboxyocta-2',4',6'-triene)-9-hydroxydrim-7-ene-11,12-olide (5), (2'E,4'E,6'E)-6-(1'-carboxyocta-2',4',6'-triene)-11,12-epoxy-9,11-dihydroxydrim-7-ene (6), cinereain (7), carnequinazolines A and B (8 and 9), carnemycin B (10), and stromemycin (11) were isolated from the fungus Aspergillus insuetus, strain BTBU20220155. The structures of the compounds were determined based on spectroscopic techniques, including 1D and 2D NMR, HRESIMS, and ECD experiments. The in vitro antimicrobial evaluation revealed that compounds 5 and 11 exhibited inhibitory activity against Candida albicans, with minimum inhibitory concentration (MIC) values of 12.5 and 25 μg/mL, respectively. These findings suggest that A. insuetus is a promising source of bioactive natural products with potential applications in antifungal therapy.

Detection of Abnormal Blood Flow Region Based on Near Infrared Correlation Spectroscopy

Blood flow measurement of microvessels in human tissues is of vital importance for the diagnosis and treatment of many diseases. In this paper, the detection method of abnormal blood flow regions based on near-infrared correlation spectroscopy is studied. We used the NL-Bregman-TV imaging algorithm to realize Blood flow imaging. However, due to the limitation of the number and distribution of detectors, the pixels obtained from images are extremely low, which cannot meet the practical requirements of the visual and the abnormal blood flow range measurement. In this paper, the bicubic interpolation method is used to improve the resolution of low-pixel blood flow images. The parameter index of the normalized similarity was proposed to help judge the effect of the interpolation method on the resolution of this kind of image. Aiming at the extraction of abnormal regions, a threshold segmentation algorithm based on the histogram difference method and a morphological processing algorithm is proposed to extract the contour of abnormal blood flow. The method proposed in this paper can be used to accurately locate and extract the clear and smooth contour of abnormal blood flow.

Rearrangement of C2-Spirooxindoles: Conversion to the 2-Hydroxyhemi-Indigo and Chromenoindole.

This study demonstrates the rearrangement of C2-spirooxindoles to the 2-hydroxyhemi-indigo and chromenoindole. The N-H-spirooxindole exhibits double proton translocation and its conversion to the (Z)-2-hydroxyhemi-indigo photoswitch with trifluoroacetic acid, while the N-methyl-spirooxindole undergoes structural rearrangement to the chromenoindole. The mechanism of the reactions was proposed, and the structure of the products was confirmed by one-dimensional (1D) and two-dimensional (2D) NMR spectra and X-ray structure analysis. The photoswitching performance of (Z)-2-hydroxyhemi-indigo, which allows the stabilization of the E-switched form by intramolecular hydrogen bonding, has been studied in solvents of different polarities. It was found that in the less polar solvents, the E-switched metastable isomer is characterized by high stability.

Fruits from Rosa roxburghii: A Valuable Bioresource of Potent Radical Scavengers and Novel Ursane-Type Triterpenoids.

Four new ursane-type triterpenoids named rosaroxine A-D and 21 known compounds were identified from Rosa roxburghii fruits. The structures of all compounds were established by 1D and 2D NMR spectroscopy and mass spectrometry. The phenolics catechin (EC50 13.4 μM), quercetin (13.1 μM), gallic acid (10.0 μM), and protocatechuic acid (15.2 μM) were identified as powerful in vitro antioxidants with EC50 values lower than ascorbic acid (31.3 μM). The triterpenoids rosaroxine C (EC50 37.4; 40.3 μM) and 2-oxo-pomolic acid (16.6; 28.2) and the phenolics catechin (53.3; 29.0), quercetin (18.8; 33.1), and gallic acid (26.3; 40.0) exerted partly higher activities in the cyclo-oxygenase (COX 1/2) assay than the positive control acetaminophen (EC50 45.0; >100 μM). The triterpenoids rosaroxine C and 2-oxo-pomolic acid also performed well in the anti-aging assay using HaCaT cells. Quantification of the bioactive compounds by LC-MS revealed concentrations of 3.08 mg kg-1 rosaroxine C, 17.40 mg kg-1 2-oxo-pomolic acid, 76.29 mg kg-1 catechin, and 5.58 mg kg-1 protocatechuic acid in the dried fruits. Overall, this work provides detailed phytochemical information, and the results from the accomplished bioassay point toward health promoting properties of these fruits.

Parkinsonia praecox bark as a new source of antibacterial and anticancer compounds

IntroductionParkinsonia praecox is used in traditional medicine to treat various diseases; however, the antibacterial and anticancer properties from its bark have not been reported. Thus, this study aimed to evaluate the antibacterial activity, cytotoxicity and chemical study of methanolic extract of Parkinsonia praecox bark (PpBM). MethodsThe PpBM antibacterial activity was determined against pathogen strains using the broth microdilution method, the cytotoxic effect was assessed on cancerous (HepG2, SKOV-3 and HeLa) and non-cancerous (J774A.1 and HaCaT) cells using the crystal violet assay, the in vitro hemotoxicity was evaluated using the hemolysis assay on human erythrocytes and the identification of major compounds derived from PpBM was performed by 1H and 13C NMR and 2D NMR experiments. ResultsPpBM (2000 µg/mL) demonstrated antibacterial activity against Listeria monocytogenes, a potential breakthrough in the fight against this pathogen. PpBM decreased cell viability of HepG2 liver cancer cells (IC50, 104.56 µg/mL) with a selectivity index of 1.38 regarding J774A.1 macrophages and 2.04 to HaCaT keratinocytes, suggesting a selective anticancer potential. On the other hand, PpBM did not cause hemolysis to high concentrations (1000 µg/mL) or alterations in the morphology of human erythrocytes at doses lower than 200 µg/mL. For the first time, lupenone, germanicone, 3-oxo-oleanane-18-en-28-ol, and combretol were identified in P. praecox. PpBM showed antibacterial, selective anticancer, and non-hemotoxic properties. These activities may be related to the major compounds, such as lupenone. ConclusionP. praecox bark is a new option for obtaining bioactive compounds, further in vitro and in vivo studies are required to confirm their efficacy and safety.

Modified Beer-Lambert algorithm to measure pulsatile blood flow, critical closing pressure, and intracranial hypertension.

We introduce a frequency-domain modified Beer-Lambert algorithm for diffuse correlation spectroscopy to non-invasively measure flow pulsatility and thus critical closing pressure (CrCP). Using the same optical measurements, CrCP was obtained with the new algorithm and with traditional nonlinear diffusion fitting. Results were compared to invasive determination of intracranial pressure (ICP) in piglets (n = 18). The new algorithm better predicted ICP elevations; the area under curve (AUC) from logistic regression analysis was 0.85 for ICP ≥ 20 mmHg. The corresponding AUC for traditional analysis was 0.60. Improved diagnostic performance likely results from better filtering of extra-cerebral tissue contamination and measurement noise.

Minor Humulane and Eremophilane Sesquiterpenoids from Syringa pinnatifolia and Their Protective Effect Against Oxidative Injuries in H9c2 Cells.

As a part of systematic research, an ongoing phytochemical investigation of the sesquiterpenoid-containing fraction led to the isolation of five new sesquiterpenoids from the peeled stems of Syringa pinnatifolia, including two pairs of enantiomeric humulane-type (±)-alashanoids A1 and B1 (1 and 2) and one eremophilane-type alashanoid C1 (3). These structures were elucidated by the analysis of extensive spectroscopic data, including ESI-MS and 1D and 2D NMR, and the absolute configuration was determined by comparing its experimental and calculated electronic circular dichroism and calculated NMR. These isolates exhibited moderate in vitro cardioprotective effects against oxidative injuries in H9c2 cells.

Characterization of Antibiotic Actinomycin D Isolated from Streptomyces parvulus Collected from Marine Sponge of Barrang Lompo Island, Makassar, Indonesia.

Microorganisms associated with sea sponges have proven to be good natural product resources that are biologically active and pharmaceutically important. This research aimed to identify actinomycetes related to a sponge from Bar-ranglompo Island Makassar and the antibacterial compounds. Identification of actinomycetes was based on molecular characterization of sequence gen16S rRNA. The antibacterial compound was separated using vacuum liquid chromatog-raphy and preparative Thin Layer Chromatography (TLC). The structure determination was done based on spectroscopy 1H-NMR, 13C-NMR, 2D NMR, and mass spectra. Molecular characterization showed that actinomycetes strain BLP 20 had the closest relationship with Streptomyces parvulus and Uncultured Streptomyces sp. with a similarity value of 83%. The results obtained from the characterization of antibacterial compounds based on spectroscopic data indicate that these compounds lead to Actinomycin D. Characterization and identification of Strain 20 / BLP by molecular phylogenetic analysis of 16S rRNA sequences revealed the closest relationship with Uncultured Streptomy-ces sp and S. parvulus with a similarity value of 83 %, which indicated a new species. The structure of the active compound isolated from actinomycetes strain 20 / BLP leads to Actino-mycin D.

Prediction of the response to antiangiogenic sunitinib therapy by non-invasive hybrid diffuse optics in renal cell carcinoma.

In this work, broadband diffuse reflectance spectroscopy (DRS) and diffuse correlation spectroscopy (DCS) were used to quantify deep tissue hemodynamics in a patient-derived orthotopic xenograft mouse model of clear cell renal cancer undergoing antiangiogenic treatment. A cohort of twenty-two mice were treated with sunitinib and compared to thirteen control untreated mice, and monitored by DRS/DCS. A reduction in total hemoglobin concentration (THC, p = 0.03), oxygen saturation (SO2, p = 0.03) and blood flow index (BFI, p = 0.02) was observed over the treatment course. Early changes in tumor microvascular blood flow and total hemoglobin concentration were correlated with the final microvessel density (p = 0.014) and tumor weight (p = 0.024), respectively. Higher pre-treatment tumor microvascular blood flow was observed in non-responder mice with respect to responder mice, which was statistically predictive of the tumor intrinsic resistance (p = 0.01). This hybrid diffuse optical technique provides a method for predicting tumor intrinsic resistance to antiangiogenic therapy and could be used as predictive biomarker of response to antiangiogenic therapies in pre-clinical models.

Experimental visualization of optical spatial sensitivity through combination of diffuse correlation spectroscopy and acoustic radiation force

In field of diffuse optics for biomedical applications, the spatial sensitivity (SS) is a key parameter to evaluate or optimize the adopted modalities, such as penetration depth, signal-to-noise ratio as well as sensor distribution. Nevertheless, SS is usually estimated via computer simulations (e.g., photon Monte Carlo simulation), rather than being quantified experimentally, due to the technical difficulty. In this study, we report the experimental measurement and visualization of optical SS through combination of acoustic radiation force (ARF) and the scanning diffuse correlation spectroscopy (DCS). By spatially varying the location of ARF focal spot within liquid phantom, the enhanced particle flow, which represents the most spatial sensitive location, was identified by DCS. The experimental outcomes were cross-validated with the photon Monte Carlo simulation, thus demonstrating its accuracy, feasibility, and potential for guiding clinical usage.

The development of machine learning approaches in two-dimensional NMR data interpretation for metabolomics applications

Metabolomics has been widely applied in human diseases and environmental science to study the systematic changes of metabolites over diverse types of stimuli. NMR-based metabolomics has been widely used, but the peak overlap problems in the one-dimensional (1D) NMR spectrum could limit the accuracy of quantitative analysis for metabolomics applications. Two-dimensional (2D) NMR has been applied to solve the 1D NMR overlap problem, but the data processing is still challenging. In this study, we built an automatic approach to process the 2D NMR data for quantitative applications using machine learning approaches. Partial least square discriminant analysis (PLS-DA), artificial neural network classification (ANN-DA), gradient boosted trees classification (XGBoost-DA), and artificial deep learning neural network classification (ANNDL-DA) were applied in combination with an automatic peak selection approach. Standard mixtures, sea anemone extracts, and mouse fecal samples were tested to demonstrate the approach. Our results showed that ANN-DA and ANNDL-DA have high accuracy in selecting 2D NMR peaks (around 90 %), which have a high potential application in 2D NMR-based metabolomics quantitively study, while PLS-DA and XGBoost-DA showed limitations in either data variation or overfitting. Our study built an automatic approach to applying 2D NMR data to routine quantitative analysis in metabolomics.

In Vitro and In Silico Analysis of PTP1B Inhibitors from Cleistocalyx operculatus Leaves and Their Effect on Glucose Uptake.

As part of our ongoing research on new anti-diabetic compounds from ethnopharmacologically consumed plants, two previously undescribed lupane-type triterpenoids (1 and 2) with dicarboxylic groups, an undescribed nor-taraxastane-type triterpenoid (3), and 14 known compounds (4-17) were isolated from the leaves of Cleistocalyx operculatus. Extensive spectroscopic analysis (IR, HRESIMS, 1D, and 2D NMR) was used for structure elucidation, while the known compounds were compared to reference data reported in the scientific literature. All the isolates (1-17) were evaluated for their inhibitory effects on the protein tyrosine phosphatase 1B (PTP1B) enzyme. Compounds 6, 9, and 17 showed strong PTP1B inhibitory activities. The mechanism of PTP1B inhibition was studied through enzyme kinetic experiments. A non-competitive mechanism of inhibition was determined using Lineweaver-Burk plots for compounds 6, 9, and 17. Additionally, Dixon plots were employed to determine the inhibition constant. Further insights were gained through a structure-activity relationship study and molecular docking analysis of isolated compounds with the PTP1B crystal structure. Moreover, all isolates (1-17) were tested for their stimulatory effects on the uptake of 2-deoxy-2-[(7-nitro-2,1,3-benzoxadiazol-4-yl) amino]-D-glucose (2-NBDG) in differentiated 3T3-L1 adipocyte cells. Compounds 6, 13, and 17 exhibited strong glucose absorption stimulation activity in a dose-dependent manner.

Targeted isolation of dimeric sesquiterpene lactones and sesquiterpene derivatives from the roots of Inula helenium

LC-HRMS/MS-based molecular networking was applied to investigate the bioactive sesquiterpene lactones and their analogs contained in Inula helenium, enabling the isolation of four undescribed eudesmane-eudesmane sesquiterpene dimers (1–4), a sesquiterpene-amino acid adduct (5), and 17 known sesquiterpenes (6–22). The structures were determined based on 1D, 2D NMR, and HRESIMS data analysis, as well as DP4+ probability analyses and ECD calculations. The biosynthetic pathway of the sesquiterpene dimers is postulated to proceed via the Diels-Alder reaction as the key step. The inhibitory activity of all isolates on LPS-induced nitric oxide (NO) production in RAW 264.7 macrophages was evaluated. Compounds 4, 17, and 20 exhibited significant inhibitory activity against NO production, with IC50 values of 8.4, 5.5, and 9.1 μM, respectively.

Dynamics of metal formation upon radiation-chemical reduction of Cd2+ ions in aqueous solutions: Morphology of cadmium precipitate

The dynamics of metal formation upon radiation-chemical reduction of Cd2+ ions in aqueous solutions in the presence of НCOONa and morphology of cadmium precipitate were studied. The dynamics process and the morphology were characterized by dynamic light scattering, photon correlation spectroscopy, scanning electron microscopy, and turbidimetry. The formation of aqueous dispersions of the metal with the initial particle size of approximately 0.20 ± 0.05 μm was demonstrated. The metal particles undergo agglomeration with time; as a result, their size increases to 2–3 μm. The process completes with the formation of the precipitate. A feature of the sediment morphology is the developed structure of its surface and high porosity. The pores (from 0.5 μm to several microns) make up 80–90% of its volume. The aggregation is accelerated with an increase in the absorbed dose (amount of reduced metal) and in the concentration of salts in the solution.

Spectroscopic and solution properties characterization of quaternary ammonium ion containing polycations complexed with fluorescent rhodamine sulfonic acid dyes

Based on the growing range of applications for polycations in research and commercial materials, a continuing need exists to advance the fundamental knowledge and understanding of this class of materials. Spectroscopic and solution properties characterizations of noncovalently labeled, fluorescent Alexa Fluor® dye complexes of two commercial polycations, poly(2-(trimethylamino) ethyl methacrylate) monocation and poly[bis[2-chloroethyl] ether-alt-1,3-bis[3-(dimethylamino) propyl] urea] dication are reported to help address this need. A variety of fluorescence spectroscopic methods are used with a special emphasis on fluorescence correlation spectroscopy (FCS) which is applied to characterize the Stokes radius (RS) and equilibrium dissociation constants (Kd) of dye-polycation complexes at nanomolar dye concentrations. Resulting RS values indicate dye binding to individual polycation chains. Measured Kd values in the sub-micromolar range are consistent with strong dye binding. Increasing solution ionic strength with sodium chloride addition inhibits dye binding and decreases the RS of dye-polycation complexes due to size collapse of polycation chains. The complexes differ in their solution stability to ionic strength changes suggesting that both electrostatic and hydrophobic binding interactions influence dye binding. This study establishes the viability of noncovalent dye-polycation complexation in concert with FCS characterization as a general approach for investigating the properties of quaternary ammonium ion containing polycations in aqueous solution.

Comparative analysis of Cr(VI) oxyanions adsorption on aged polyamide microplastics: Evaluating UV irradiation versus chemical aging

Microplastics (MPs) commonly undergo aging in various environmental media, affecting both their environmental behavior and Trojan-horse effect for contaminants. However, the mechanisms underlying the different impact of various aging processes on the Trojan-horse effect of polyamide (PA) MPs towards metal oxyanions remain unclear. This study explored how chemical aging and UV irradiation impact the structural characteristics and Cr(VI) adsorption of PA MPs under various influencing factors. Results showed that both aging processes enhanced the negative surface charge, surface oxygen content, and roughness of PA MPs, with FTIR correlation spectroscopy confirming an increase in O-containing functional groups. Cr(VI) adsorption onto aged PA sharply increased by 17.4 % (14 days of UV irradiation), 39.4 % (42 days of UV irradiation), and 21.7 % (chemical aging) compared to original PA. Salinity and natural organic matter had adverse effects on Cr(VI) adsorption. Spectroscopic analyses highlighted the crucial role of hydrophilic amide groups in controlling Cr(VI) adsorption onto aged PA, involving hydrogen bonding, electrostatic interactions, and reduction. Aged PA exhibited higher adsorption capacities but also greater desorption under simulated seawater and intestinal fluid, suggesting increased migration potential for Cr(VI). This study provides helpful insights into assessing the environmental risk of co-existing PA MPs and metal oxyanions, particularly considering the effect of aging processes.

Room-Temperature Solution Fluorescence Excitation Correlation Spectroscopy.

Single-molecule fluorescence spectroscopy is a powerful tool for investigating the physical properties of individual molecules, yet elucidating the fast fluctuation dynamics of freely diffusing single molecules in solution at room temperature, where a variety of chemical and biological processes occur, remains challenging. In this study, we report on fluorescence excitation correlation spectroscopy of room-temperature solutions, which enables the study of spontaneous fluctuation of the excitation spectrum with microsecond time resolution. By employing Fourier transform spectroscopy with broadband femtosecond pulses and time-correlated single-photon counting, we achieved fluorescence excitation spectroscopy of a room-temperature solution at the single-molecule level. Building upon this single-molecule measurement, we obtained an excitation wavelength-resolved fluorescence autocorrelation function in the microsecond to millisecond range, demonstrating the potential of this method to elucidate fast, spontaneous, time-dependent changes of excitation spectra in statistically equilibrated systems. With further development, this method will allow the study of spectral exchange associated with transitions between sub-ensembles of solution-phase molecules with unprecedented time resolution.