Proton NMR Spectra Research Articles

Assessment of Conjugation Pathways in N-Methylporphyrins that Are Fused to Acenaphthylene, Phenanthrene, or Pyrene: Evidence for the Presence of Alternative Aromatic Circuits.

Acenaphtho-, phenanthro-, and pyrenopyrrole esters, readily available from Barton-Zard reactions of ethyl isocyanoacetate with nitroarenes, were reacted with methyl iodide and KOH in DMSO to give N-methylpyrroles and subsequent cleavage of the ester moieties was accomplished with KOH in ethylene glycol at 200 °C. Condensation with two equiv of an acetoxymethylpyrrole in refluxing acetic acid-2-propanol afforded a series of annulated tripyrranes. Cleavage of the terminal tert-butyl ester groups with trifluoroacetic acid, followed by condensation with a diformylpyrrole and oxidation with FeCl3, gave N-methyl acenaphtho-, phenanthro-, and pyrenoporphyrins. The N-methyl substituent effectively freezes the tautomeric equilibria to maximize interactions between the porphyrin nucleus and the fused aromatic substructures. Analysis of the proton NMR spectra provides evidence of the presence of extended aromatic circuits within these structures. Anisotropy of induced ring current (AICD) plots clearly shows the presence of 30π electron pathways in phenanthro- and pyrenoporphyrins that run around the exterior of the benzenoid fragments. These results demonstrate that N-alkylation can be used to relocate aromatic pathways in porphyrinoid systems.

Neural net analysis of NMR spectra from strongly-coupled spin systems

Extracting parameters such as chemical shifts and coupling constants from proton NMR spectra is often a first step in using spectra for compound identification and structure determination. This can become challenging when scalar couplings between protons are comparable in size to chemical shift differences (strongly coupled), as is often the case with low-field (bench top) spectrometers. Here we explore the potential utility of AI methods, in particular neural networks, for extracting parameters from low-field spectra. Rather than seeking large experimental sets of spectra for training a network, we chose quantum mechanical simulation of sets, something that is possible with modern software packages and computer resources. We show that application of a network trained on 2-D J-resolved spectra and applied to a spectrum of iduronic acid, shows some promise, but also meets with some obstacles. We suggest that these may be overcome with improved pulse sequences and more extensive simulations.

Preparation of trimethoprim/methyl β-cyclodextrin complexes, in vitro and in vivo pharmacokinetic study, and evaluation of antibacterial activity in combination with the complex of sulfamethoxazole/methyl β-cyclodextrin

Through cyclodextrin selection from phase solubility study, complexation method screening, and complexation condition optimization by using single and orthogonal strategy, the complexes of trimethoprim with methyl β-cyclodextrin, HP β-cyclodextrin and HP-γ-cyclodextrin with the best solubility increasing so far were prepared and confirmed by FTIR, DSC and proton NMR spectra. The in vitro pharmacokinetic study showed that trimethoprim was 80 %–90 % released in three complexes in 20 min., and in their dog's in vivo pharmacokinetic study, the Cmax was increased from 0.22 µg/mL to 0.85 µg/mL, 0.7 µg/mL and 0.72 µg/mL, the AUC0∼40 was increased from 2.35 µg*h/mL to 3.94 µg*h/mL, 5.06 µg*h/mL and 6.73 µg*h/mL, the LC was shorten from 2.17 L/kg/h to 0.89 L/kg/h, 0.56 L/kg/h and 1.07 L/kg/h for the complexes with methyl β-cyclodextrin, HP β-cyclodextrin and HP-γ-cyclodextrin respectively. After combination with sulfamethoxazole cyclodextrin complex, the antibacterial activity of the complex of trimethoprim with methyl β-cyclodextrin was increased significantly compared with the pure drug alone, indicated that this complex can be used as new potent antibacterial agent.

Sonochemical synthesis, characterization, and ADMET studiesof Fe (II) and Cu (II) nano-sized complexes of trimethoprim

Nanoparticles exhibit distinct physical and chemical characteristics and are becoming increasingly significant in the production of innovative nanodevices for many applications in physics, biology, biomedicine, and pharmaceuticals. The aim of this research work is to synthesize Fe (II) and Cu (II) nano-sized complexes of trimethoprim (TMP) using the sonication method, characterize them using physical and spectroscopic methods, and carry out ADMET studies on the synthesized complexes. The spectroscopic and physical studies showed a change in colour and an increase in melting point due to coordination. The novel compounds were slightly soluble in water. The XRD tests revealed that the new nanocomplexes were crystalline. The Fe (II) nanocomplexes had a size of 57.56 nm and the Cu (II) nanocomplexes had a size of 69.88 nm. These values were found using Debye-Scherrer’s equation. The FTIR results of the TMP, Fe (II), and Cu (II) nanometal complexes showed a shift of the amino group band from 3317 to 3295 and 3202 cm?1 and the azomethine band from 1633 to 1625 and 1592 cm?1 in the complexes. In the complexes, the proton NMR spectra revealed an upfield shift of the amine proton. The carbon-13 NMR spectra showed that CH2 was involved in coordination with the metal ions. The spectra studies indicated that TMP coordinated with the metal ions through the methylene and amino groups. A trigonal bipyramid structure was proposed for the complexes. The results of the Rule of 5 studies indicated that the test compounds had a good drug-likeness prediction, with only one violation. The ADMET prediction showed that all of the compounds demonstrated improved pharmacokinetic characteristics and adhered to the RO5 requirement. These findings highlight the therapeutic potential of Fe (II) and Cu (II) nano-sized TMP complexes as bioactive compounds that warrant further investigation for pharmaceutical applications.

Synthesis, characterization, and investigation of catalytic properties of RuII complexes with Schiff bases based on 2-hydroxybenzaldehyde and 5-bromo-2-hydroxybenzaldehyde

Pursuing our recent interest concerning the catalytic activity of half-sandwich RuII complexes containing Schiff base ligands (L1 and L2), in this study new Schiff bases and their half-sandwich RuII complexes were prepared. The structures of these compounds were confirmed by a variety of spectral and physical methods such as microanalysis, FT-IR, electronic spectra, proton and carbon NMR, TGA and mass spectra. The catalytic activities of the RuII complexes toward the transfer hydrogenation of ketones to their corresponding alcohols were investigated using i-PrOH as a hydrogen source and solvent. The complexes showed high catalytic activities at catalyst concentrations of 0.01 mmol and were able to carry out transfer hydrogenation (TH) to a wide range of ketones in the presence of KOH. In general, Schiff bases recognition, the coordination chemistry, and the ketone substrates were found to influence the catalytic performance of these complexes.

Diisopropylammonium hydrogen squarate: Synthesis and comprehensive analysis of non-linear optical co-crystal using X-ray, Hirshfeld, mechanical, optical and DFT methods

This research successfully synthesized a single co-crystal of diisopropylammonium hydrogen squarate using prolonged vaporization for crystal growth. Single-crystal X-ray spectrometry confirmed its monoclinic structure, and morphological predictions were made. UV–visible spectroscopy revealed its optical transmittance with a direct optical energy band gap of 3.45 eV. Photoluminescence studies showed a strong violet emission at 402 nm when excited by a 260 nm source. Microhardness study examined the crystal's mechanical attributes portraying the normal indentation size effect followed by a qualitative overview of half-penny crack dynamics. FTIR study aided in the discernment of varied vibrational modes with NH stretching being observed at 3078 cm−1. Thermal examination further revealed the crystal's stability up till 244 °C. Proton and carbon-13 NMR spectra were analyzed to verify the presence of functional groups and the overall molecular integrity. Intermolecular interactions were analyzed using Hirshfeld surface and fingerprint mapping. The Z-scan technique demonstrated the crystal's applicative potential in its third harmonic generation capability. Theoretical calculations with Density Functional Theory (DFT) supported the experimental findings, offering insights into optimized geometries, frontier molecular orbitals, natural population and bond orbital distributions, hyperpolarizability, molecular electrostatic potentials, IR vibrational modes, and UV absorbance profiles.

Substituent effect on discriminative detection of Mg2+ and Zn2+ ions by two related coumarin-based chemosensors

Two closely related coumarin-based chemosensors, L1 with a –NO2 group and L2 with an −I group, have been designed as the fluorescent sensors. Chemosensors L1 and L2 have been utilized for the selective detection of Mg2+ and Zn2+ ions, respectively. The non-fluorescent L1 and L2 exhibit ‘turn-on’ fluorescence response with Mg2+ and Zn2+ ions, respectively. The absorption spectrum of L1 in presence of Mg2+ ion exhibits a 12 nm blue-shift while L2 shows a 5 nm red-shift with Zn2+ ion. Chemosensors L1 and L2 show noteworthy detection limits of 0.10 and 0.35 μM and binding constants (Kb; ×104 M−1) of 0.45 and 1.14 for Mg2+ and Zn2+, respectively. The chemosensor-metal binding was studied by mass and proton NMR spectra while a 2:1 stoichiometry was confirmed by Job’s plot. The crystal structure of [(L2)2Zn] complex further confirms a 2:1 stoichiometry as well as binding mode of the chemosensors. Both chemosensors further worked as the colorimetric sensors for the detection of Mg2+ and Zn2+ ions. For both chemosensors, reversibility was achieved by using ATP while logic gates were also generated. Chemosensor L2 was found to be AIEE active in MeOH-H2O and EtOH-H2O solvent systems. Water promoted H-type aggregation by hindering the −CN bond rotation which enhanced the emission. The formation of aggregates was confirmed by the dynamic light scattering and florescence lifetime measurements.

Heme-catalyzed degradation of linoleate 9-hydroperoxide (9-HPODE) forms two allylic epoxy-ketones via a proposed pseudo-symmetrical diepoxy radical intermediate

Heme-initiated decomposition of unsaturated fatty acid hydroperoxides creates alkoxyl radicals that propagate a complex series of reactions to hydroxy, keto, epoxy and aldehydic products. Herein, among the products from the hematin-catalyzed degradation of 9-hydroperoxy-linoleic acid (9-HPODE), we observed a double peak on normal-phase HPLC that resolved on RP-HPLC into equal proportions of two epoxy-allylic ketones with identical UV spectra. Their proton NMR spectra were also indistinguishable and consistent with 9,10-trans-epoxy-11E-13-keto- and 9-keto-10E-12,13-trans-epoxy-octadecenoic acids. Acid hydrolysis to the corresponding dihydroxy-ketones and GC-MS analysis identified the earlier eluting product on RP-HPLC as the 9,10-epoxy regio-isomer. Starting from the C9-hydroperoxide, recovery of the two epoxy-ketones in equal proportions suggests their formation from a common intermediate. Earlier work has proposed formation of a pseudo-symmetrical diepoxy radical (9,10-epoxy-11(•)-12,13-epoxy, derived from an epoxy allylic hydroperoxide precursor) in the carbon chain fragmentation leading to aldehydic products. This intermediate in pathways of alkoxyl radical reactions forms equal pairs of aldehydes, and now also a pair of epoxy-ketones, and based on mechanism the same products arise from either 9-HPODE or 13-HPODE. Our results point to the intermediacy of this diepoxy-carbinyl radical in the origin of at least two classes of linoleate peroxidation products, and it should be considered as a viable intermediate for homo-conjugated diene peroxidation in general. The reactions could contribute to the aldehydes and epoxy-ketones in tissues undergoing oxidative transformations of polyunsaturated fatty acids.

1H NMR SPECTRAL CHARACTERISTICS OF PYRIDO[1,2-A]BENZIMIDAZOLE AND ITS DERIVATIVES

A systematic study of proton NMR spectra of pyrido[1,2-a]benzimidazole and 65 of its mono-, di- and poly-substituted derivatives with substituents in the pyridine and/or benzene fragment was carried out. The choice of certain structures is related to the great practical significance, as well as the complexity of interpreting their 1H NMR spectra. As a result of the research, a number of general patterns of arrangement (characteristic ranges) on the scale of chemical shifts of signals of hydrogen atoms associated with the nucleus of the studied heterocycles have been established. In the 1H NMR spectrum of pyrido[1,2-a]benzimidazole and most of its derivatives, the H1 signal of the pyridine cycle associated with a carbon atom was released in the weakest field, which experienced a strong electron acceptor effect of the nodal endocyclic nitrogen atom. The signal of another heteroaromatic proton H2 was usually detected in the strongest field region of the spectrum. The H8 signal had the smallest chemical shift among the aromatic protons. As the analysis of 1D 1H NOE spectra of a series of pyrido[1,2-a]benzimidazoles showed, this position of the heterocycle was the reaction center for the introduction of an electrophilic particle under SEAr reaction conditions. The H9 signal was detected in a weaker field relative to other aromatic protons. The influence of the electronic nature of the substituent and its position in the condensed heterocycle on the distribution of the electron density in the molecule has been established. It is concluded that the transmission of electronic effects of substituents in pyrido[1,2-a]benzimidazoles differs from benzoid systems. A number of controversial proton signals were attributed by means of 1H-1H NOESY and 1H-15N HMBC spectroscopy. The conducted studies will allow to use the data of 1H NMR spectroscopy to determine potential reaction centers in pyrido[1,2-a]benzimidazoles and other similar condensed pyridine derivatives with a nodal nitrogen atom. For citation: Begunov R.S., Fakhrutdinov A.N., Sokolov A.A., Savina L.I., Bashkov N.E. 1H NMR spectral characteristics of pyrido[1,2-a]benzimidazole and its derivativese. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2024. V. 67. N 5. P. 43-53. DOI: 10.6060/ivkkt.20246705.6971.

Comprehensive computational insights on the conformations, electronic properties and binding mechanism of mescaline: A hallucinogenic molecule

In the series of computational investigations of hallucinogenic compounds particularly in unraveling their conformational aspects, mescaline is taken up in this report after having studied psilocybin and psilocin. Six conformers were identified from the relaxed scan of the dihedral angles of which two were taken up for studying their chemical properties. The two low energy conformers differed by about 0.5 kcal.mol-1 at B3LYP/cc-pVTZ and 1.5 kcal.mol-1 at CCSD/cc-PVDZ levels of theory, respectively and structurally the two conformers differ by the orientation of the alkyl amine group vis-à-vis the benzene ring via the N–H---π interaction. Natural Bond Orbital calculations unveiled the existence of intra-molecular π → π*, n → π* charge transfers, and some hyperconjugative interactions that significantly enhance the stability of mescaline. Reduced Density Gradient calculations unraveled the occurrence of strong intramolecular N–H---π interaction in the most stable conformer of mescaline. The calculated geometrical parameters and predicted structure of the most stable conformer of mescaline agree significantly well with the earlier reported conformers from X-ray studies of mescaline. The computed λmax in the UV–visible spectrum, peak positions in the proton NMR spectrum, and vibrational modes exhibit excellent agreement with the previously reported experimental findings. Moreover, we utilized molecular docking and molecular dynamics simulations to elucidate the binding mode and molecular mechanism of mescaline in comparison to other hallucinogenic molecules. Our findings revealed that mescaline displayed a favorable binding energy and induced essential conformational changes, indicating a potential common mechanism of action shared with psilocybin, another hallucinogenic compound.

Joel Hooper.

"I'm always in a good mood when I see a really clean proton NMR spectrum… The most challenging part of my job is when my students have a prolonged period of unsuccessful experiments…" Find out more about Joel Hooper in his Introducing… Profile.

Spectroscopic (FT-IR, FT-Raman, NMR and UV–vis), quantum calculation, molecular structure, solvent interaction, ADME and molecular docking investigation on 4-oxo-4h-1-benzopyran-2-carboxylic acid

The present work, spectroscopic and quantum computational study has been carried out for the molecule 4-oxo-4H-1-benzopyran-2-carboxylic acid. The stable conformer of the title molecule was identified using Potential Energy Surface (PES) scan. The structural and geometrical parameters of the stable conformer of the molecule were determined by Density Functional Theory (DFT) using B3LYP method along with the basis set 6-311++G(d,p) through Gaussian 09 W software. The theoretical and experimental investigations such as Vibrational (FT-IR and FT-Raman), UV–visible and NMR analysis were done. The FT-IR were recorded in the region of (4000–400 cm−1) and FT-Raman in the region of (4000–100 cm−1), and the vibrational bands were compared with the theoretical values. Carbon NMR and Proton NMR spectra have been analyzed in DMSO solution. The theoretical chemical shift values were determined using Gauge Independent Atomic Orbital (GIAO) method. The intermolecular and intra-molecular bonding of orbitals and transfer of charge were studied using the Natural Bond Orbital (NBO) analysis. The respective transitional study was done through UV–vis's spectra and theoretical values predicted using TD-DFT (Time Dependent – DFT) method for both gas and solvent (ethanol) state. HOMO (Highest Occupied Molecular Orbital) – LUMO (Lowest Unoccupied Molecular Orbital) energy gap results prove the exchange of charges inside the molecule. Molecular Electrostatic Potential (MEP) is used to identify the nucleophilic and electrophilic sites of the molecule. To check the bioactive nature of the title molecule the drug-likeness was determined. Molecular docking is used to analyze the biological activity of the title molecule. The distribution of torsional angles in a protein structure is viewed by the Ramachandran plots of the molecules.

Nuclear magnetic resonance analysis of extra virgin olive oil: classification through secoiridoids.

Extra virgin olive oil (EVOO), a natural product with a multidisciplinary role, has been and is continuing to be studied from several points of view. Among them, its chemical analysis is of major importance and several methods have been used. Nuclear magnetic resonance (NMR) spectroscopy has inherent advantages, among them monitoring the chemical constituents without the need for a separation technique and without, for instance, possible carry-over effects. Additionally, several magnetic resonance spectroscopic techniques can provide a novel powered insight into the nature and properties of a sample under study. Moreover, -omics procedure can reveal new information and can lead to the classification of populations under study. The main objective of the present work was the possible classification of the EVOO samples based on their aldehyde content using a proposed unreferenced 1 H-NMR spectroscopic quantification method combined with a metabolomic approach. Moreover, the study of the impact of such elevated aldehyde content on several spectra regions of importance in the proton NMR spectra led to the proposal of a possible new isomer indicator. Univariate analysis of 12 EVOO samples showed that oleacein, oleocanthal, elenolic acid, hydroxytyrosol/hydroxytyrosol derivatives and tyrosol/tyrosol derivatives strongly differentiated two classes of EVOO: OEH (for high aldehyde EVOO content) and OE (for non-high aldehyde content). Moreover, we pointed out the 'impact' of such elevated secoiridoid and derivatives content, through their moieties' units, on a range of several resonances of the 1 H-NMR spectrum. The metabolomic approach demonstrated the classification of EVOO samples based on their secoiridoid and derivatives content. Multivariate analysis showed a strong influence on the discrimination of the EVOO classes based on the protons resonating at the aldehyde region of the 1 H-NMR spectrum; the aldehyde protons corresponding to 5S,4R-ligstrodial and 5S,4R-oleuropeindial, oleacein, oleocanthal, elenolic acid, p-HPEA-EA, 3,4-DHPEA-EA, 5S,4R- and 5S,4S-ligstrodial and the proton corresponding to a new compound were reported for the first time. This isomer compound, reported for the first time, could serve as a possible indicator for EVOO classification. An unreferenced quantification method was proposed and EVOO samples were classified into two classes: OEH and OE, according to their aldehyde content, gaining thus probably higher nutrient and possible pharmacological value. Moreover, we point out the 'impact' of such elevated aldehyde content on several spectral regions of the 1 H spectrum. Finally, a new compound was detected in the OEH samples and is reported for the first time. This compound could possibly be an indicator. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Implementation of pure shift 1 H NMR in metabolic phenotyping for structural information recovery of biofluid metabolites with complex spin systems.

NMR spectroscopy is a mainstay of metabolic profiling approaches to investigation of physiological and pathological processes. The one-dimensional proton pulse sequences typically used in phenotyping large numbers of samples generate spectra that are rich in information but where metabolite identification is often compromised by peak overlap. Recently developed pure shift (PS) NMR spectroscopy, where all J-coupling multiplicities are removed from the spectra, has the potential to simplify the complex proton NMR spectra that arise from biosamples and hence to aid metabolite identification. Here we have evaluated two complementary approaches to spectral simplification: the HOBS (band-selective with real-time acquisition) and the PSYCHE (broadband with pseudo-2D interferogram acquisition) pulse sequences. We compare their relative sensitivities and robustness for deconvolving both urine and serum matrices. Both methods improve resolution of resonances ranging from doublets, triplets and quartets to more complex signals such as doublets of doublets and multiplets in highly overcrowded spectral regions. HOBS is the more sensitive method and takes less time to acquire in comparison with PSYCHE, but can introduce unavoidable artefacts from metabolites with strong couplings, whereas PSYCHE is more adaptable to these types of spin system, although at the expense of sensitivity. Both methods are robust and easy to implement. We also demonstrate that strong coupling artefacts contain latent connectivity information that can be used to enhance metabolite identification. Metabolite identification is a bottleneck in metabolic profiling studies. In the case of NMR, PS experiments can be included in metabolite identification workflows, providing additional capability for biomarker discovery.

Synthesis, crystal structure and spectroscopic characterization of the Co(II) bis(pyridine) “picket fence” porphyrin complex. Potential application as antibacterial agent

In this work, we describe the synthesis, spectroscopic and structural properties of the new compound bis(pyridine)(α, β, α, β-tetrakis (o-pivalamidophenyl) porphyrinato) cobalt (II) [CoII(TpivPP)(py)2] (I). The molecular structure determined by X-rays of the compound shows that this species is a six-coordinate cobalt (II) metalloporphyrin. The UV–visible spectrum of (I) shows that the value of the Soret band (415 nm) is shifted towards the green with respect to the free base H2TpivPP while the λmax values of the Q band are 530 and 563 nm. The proton NMR spectrum of (I) clearly indicated that these derivatives are cobalt(II) paramagnetic porphyrin complexes. Zones of inhibition are studied against the bacterial strains Escherichia coli, Streptococcus pneumoniae and the fungal strains Aspergillus niger, Aspergillus fumigatus. The reported results show that cobalt porphyrin has better antibacterial and antifungal efficacy against gram-positive and gram-negative strains of bacteria as well as fungal strains.

Synthesis, DFT study, molecular docking and larvicidal activity of Chitin inhibitor alanine derived compounds

In order to obtain an effective larvicidal against A. aegypti the vectors for Dengue, Zika and Chikungunya virus, Sodium 2-{(E)-[(2-hydroxy-3-methoxyphenyl) methylidene] amino} propanoate (NaLH) ligand and its Cu(II) complexes derived from alanine amino acid with and without coligand (C1 &C2) have been synthesized. All three molecules were characterized by physicochemical techniques including FTIR, UV–Vis, proton NMR and Mass spectrum. The geometry optimization and frontier orbitals HOMO, LUMO and band gaps were calculated by using B3LYP functional and SVP basis sets for all three compounds (NaLH, complex C1 and C2). The values of HOMO/LUMO energies observed were −4.2/−1.7 eV for ligand, −5.2–3.5 eV for C1 and −5.0/−3.7 eV for C2 and corresponding values of energy gaps were 2.5 eV, 1.7 eV and 1.3 eV for NaLH, C1 and C2 respectively which increases in the following order NaLH > C1 > C2. Complex1 has been arranged in slightly distorted octahedral geometry while complex2 acquired a square pyramidal geometry. Molecular docking study of the reported larvicidal against insect acetylcholistenerase (PDB id: 6ARY) and Chitin acetylase (PDB id 5ZNT) revealed significant free energy of binding in the active site of target molecules with binding energy of −6.14 & −10.20Kcal/mol and −6.79 & −11.75Kcal/mol for C1 &C2 respectively. In addition, Larvicidal activity of complex 2 was observed with 100% mortality rate in just 2 hrs time using 1.0% concentration of larvicide. The LC50 value is 0.0015 µg/mL while LC90 value is 0.0018 µg/mL for C2. The complexes were observed to be lethal against Chitinous body layer of larvae of Aedes aegypti, the vectors for Dengue, Zika and Chikungunya virus.

Isolation and Characterization of Chemical Compounds from the Stem Bark Fractions of Citrus Grandis and Evaluation of Their Antimicrobial, Cytotoxic, and Antioxidant Activities

Citrus grandis belongs to the Rutaceae family and is a naturally occurring citrus plant. The fractionated crude extracts of C. grandis have been studied for the investigation of its phytochemicals and allowed for the evaluation of biological activities, especially antimicrobial, cytotoxic, and antioxidant activities. At first, we assessed the antibacterial and antifungal properties using the disc diffusion method and conducted cytotoxicity screening using the brine shrimp lethality bioassay. Among the raw extracts, we isolated two compounds named CG-F3-B1 and CG-F3-B2 through column chromatographic separation of the chloroform extract. By comparing their proton NMR spectra with published spectra, we identified the chemical structures of these compounds as Zeylenol and Limonin, respectively. Regarding antibacterial testing, we observed that the methanol soluble fractions and petroleum ether fractions exhibited mild to moderate activity against bacteria. Additionally, the ethyl acetate soluble fraction showed moderate antibacterial activity. In addition, the crude extract displayed moderate antifungal activity against specific fungi. Furthermore, the cytotoxic assay revealed a relevant cytotoxic effect of a crude extract with an LC50 value of 37 μg/ml. The antioxidant activity was determined using the DPPH assay, and the methanol soluble extract exhibited modest antioxidant activity with an IC50 value of 89 μg/ml. Our findings demonstrated that the stem bark fractions and isolated compounds from C. grandis exhibited various promising biological activities, including antibacterial, antifungal, cytotoxic, and antioxidant properties.
 Bioresearch Commu. 9(2): 1320-1329, 2023 (July)

Graphical exploration of 600- and 60-MHz proton NMR spectral datasets from ground roast coffee extracts.

This article uses a variety of graphical and mathematical approaches to analyse 600- and 60-MHz ('benchtop') proton NMR spectra acquired from lipophilic and hydrophilic extracts of roasted coffee beans. The collection of 40 authenticated samples comprised various coffee species, cultivars and hybrids. The spectral datasets were analysed by a combination of metabolomics approaches, cross-correlation and whole spectrum methods, assisted by visualisation and mathematical techniques not conventionally employed to treat NMR data. A large amount of information content was shared between the 600-MHz and benchtop datasets, including in its magnitude spectral form, suggesting the potential for a lower cost, lower tech route to conducting informative metabolomics studies.

Water-soluble PEG segmented mannose-based macromolecules: Synthesis, characterization and their biocompatibility

The macromolecular architectures, namely mannose-based methacrylate acetyl-mannopyranoside and PEG block copolymers [AB type copolymer [PEG-b-PMAM], poly(ethyleneglycol)-b-poly(methacryl-2,3,4,6-tetra-O-acetyl-D-mannopyranoside) and ABA type copolymer [PMAM-b-PEG-b-PMAM], poly(methacryl-2,3,4,6-tetra-O-acetyl-D-mannopyranoside)-b-poly(ethyleneglycol)-b-poly(methacryl-2,3,4,6-tetra-O-acetyl-D-mannopyranoside)] were synthesized by atom transfer radical polymerization (ATRP) method that were deacetylated to generate the corresponding water-soluble and biocompatible glycopolymer macromolecules. The molecular weight of acetyl and deacetylate macromolecules was in the range of 7083–9499 and 4659–6026, as determined by GPC and proton NMR spectra. The 5 % decomposition temperatures for acetylated methacrylate macromolecules (218–299 °C) were higher than the corresponding water-soluble macromolecules (204–248 °C). The conjugation of poly(methacryl-2,3,4,6-tetra-O-acetyl-D-mannopyranoside) (PMAM) segment with the PEG block decreased the glass transition (Tg) value, and the water-soluble macromolecules displayed Tg in the range of 92–95 °C. The biocompatibility of the synthesized water-soluble mannose-based macromolecules was determined using Human Bone Derived Cells (HBDC) culture with the TCP (Tissue culture plastic) template as control. Using three different concentrations of the synthesized glycopolymers, HBDC's were cultured for 1, 3, and 7 days. The effect of mannomethacrylate macromolecules on mitochondrial activity of HBDC's was estimated using colorimetry that showed the conversion of MTS [3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyl-tetrazolium-bromide] to formazan (MTS assay). ABA type diblock copolymer architecture exhibited increased absorbance values of 3 and 7 day cultures at 1–100 M concentrations, with the highest values observed at a concentration of 1 M for day 3 cultures. The design of these novel mannose-based macromolecules is important for improving cell proliferation, cell adhesion, and osteointegration efficiency.

Physicochemical transformation of graphene oxide during heat treatment at 110–200 °C

Graphene oxide (GO) was subjected to different heating pathways to investigate water removal at 110°C (GO-110), water removal followed by removal of surface groups at 140°C or 200°C (GO-110-140 or GO-110-200), and simultaneous removal of water and surface groups at 140°C or 200°C (GO-140 or GO-200). Physicochemical characteristics of GO samples at each stage were determined to quantify and understand the impact of each treatment pathway on porosity development, physical structure, or surface chemistry of GO. Surface elemental composition showed the following order for C/O ratio: GO-140-200 > GO-110-200 > GO-200, suggesting that a two-step heat treatment results in more oxygen removal from the surface, and FTIR profiles confirmed the lowest intensities of all functionalities for GO-140-200. Proton NMR spectra of as-received and heat-treated GO samples confirmed near complete removal of water and hydroxyl groups for samples treated at 200°C. XRD results showed that the interlayer spacing of GO reduced from 0.792 nm to the lowest values of 0.371 nm for GO-200 and 0.367 nm for GO-110-200. Porosity characterization revealed that only two pathways, GO-200 and GO-110-200, created a porous structure. Further analysis of data suggested that exfoliation is primarily triggered by decomposition of surface functionalities and release of a substantial volume of CO2/CO, but water vapor release helps to enhance the exfoliation. These results demonstrate that direct and rapid heat treatment of GO at 200°C (or higher temperatures) is the most effective option for developing a porous structure.