Electron Impact Mass Spectrometry Research Articles

Synthesis, Characterization, DPPH Radical Scavenging, Urease Enzyme Inhibition, Molecular Docking Simulation, and DFT Analysis of Imine Derivatives of 4-formylpyridine with Selective Detection of Cu+2 Ions.

This study aimed to prepare three imine derivatives (1, 2, and 3) via a condensation reaction of phenyl hydrazine, 2-hydrazino pyridine, and 4-methoxy aniline with 4-formyl pyridine. Electron impact mass spectrometry (EIMS), proton nuclear magnetic resonance (1H-NMR), ultraviolet-visible (UV-Vis) and Fourier transform infrared (FTIR) spectroscopy were utilized for the characterization. The chemosensing properties of [4((2-phenyl hydrazono)methyl) pyridine] (1), [2-(2-(pyridin-4-ylmethylene)hydrazinyl) pyridine] (2), and [4-methoxy-N-yl methylene) aniline] (3) imino bases have been explored for the first time in aqueous media. The photophysical properties of chemosensors (1, 2, and 3) were examined by various cations (Na+, NH4+, Ba+2, Ni+2, Ca+2, Hg+2, Cu+2, Mg+2, Mn+2, and Pd+2). The chemosensor (1) showed very selective binding capability with copper ions at low concentrations (20 μM) without the influence of any other mentioned ions. The maximum complexation was noted with Cu+2 and 1 at pH between 7 to 7.5. The stoichiometry binding ratio between chemosensor (1) and Cu+2 was determined by Job's plot and it was found to be 1:2. The current study explored the use of these Schiff bases for the first time as heterocyclic chemosensors. DPPH radical scavenging, urease enzyme inhibition activities, molecular docking simulation, and density functional theory (DFT) analysis of compounds 1, 2, and 3 were also conducted.

Exploring Triazole-Connected Steroid-Pyrimidine Hybrids: Synthesis, Spectroscopic Characterization, and Biological Assessment.

Molecules originating from natural sources are physicochemically and biologically diverse. The conjugation of two active biomolecules has become the foundation for medical and pharmaceutical sciences. An effective synthesis of 11 new steroid-pyrimidine conjugates containing 1,2,3-triazole rings was carried out. The group of 3α-OH bile acids (lithocholic, deoxycholic, cholic) and 3β-OH sterols (cholesterol, cholestanol) were respectively modified to azidoacetates. 2-thiouracil was converted into N(1)S and N(3)S dipropargyl derivatives. Azide-alkyne cycloaddition in the presence of copper(I) of the obtained compounds led to the preparation of 1,2,3-triazole derivatives. Based on a series of spectroscopic (1H NMR, 13C NMR, Fourier-transform infrared (FT-IR)), spectrometric analyses (Electrospray ionization-mass spectrometry (ESI-MS), electron impact-mass spectrometry (EI-MS)), and semiempirical calculations, the structures of all compounds were confirmed. In silico biological tests and molecular docking (for domain 1KZN, 2H94, 5V5Z, 1EZF, 2Q85) were performed for selected compounds. The tests performed indicate the theoretical antimicrobial potential of the obtained ligands.

Synthesis, Spectral Analysis and Molecular Docking Investigation of Thiadiazole Based Sulfonamide Derivatives: An Effective Approach Toward Alzheimer's Disease

AbstractAlzheimer's disease (AD), a neurodegenerative condition is expected to affect 152 million in 2050. The current study comprises the evaluation of thiazole based thiadiazole bearing sulfonamide derivatives to treat Alzheimer's disease. A series of compounds (1‐15) were synthesized and were studied for their anti‐Alzheimer's potential. Their IC50 values lie in the range between (19.20±0.20 nM–2.50±0.20 nM) for AChE and (19.80±0.20 nM–3.30±0.50 nM) for AChE. Among all of them, analog 2, 7, 9, and 15 were reported to possess significant activity. Among all the members of series, compound 15 having IC50=2.50±0.20 nM and 3.30±0.50 nM for AChE and BuChE, respectively, emerged as the most promising candidate due to the presence of two electronegative fluorine (F) atoms. The small and highly electronegative fluorine atoms have the ability to block the enzyme's activity by forming strong hydrogen bonds with the amino acids of the target enzymes, thereby inhibiting their function. The efficacy of these novel compounds was studied in comparison to the standard drug donepezil having IC50=5.80±0.30 nM for AChE and IC50=6.30±0.81 nM BuChE. For further assessment of inhibition potential and mode of inhibition, molecular docking study of all the potent compounds was carried out. Further, the structural identity of the synthesized compounds was confirmed using various spectroscopic techniques, including 1H‐NMR, 13C‐NMR, and High‐Resolution Electron Impact (HREI) Mass spectrometry, which provided detailed information about their molecular structure. ADME analysis of all the synthesized compounds confirmed their potential as drugs, indicating favorable pharmacokinetic properties and a promising drug profile.

Structural elucidation of tramadol, its derivatives, and metabolites using chemical derivatization and liquid chromatography-high-resolution tandem mass spectrometry.

Tramadol (T) is a strong painkiller drug that belongs to the opioid analgesic group. Several accidental intoxication cases after oral administration of T have been reported in the past decade. Tramadol, its derivatives, and metabolites present information-limited mass spectra with one prominent peak representing the amine-containing residue; therefore, their structural determination based on both electron impact mass spectrometry (EI-MS) and ESI-MS/MS spectra could be misleading. A novel analytical method for the structural elucidation of tramadol, its four homologs, and its two main phase I metabolites (N-desmethyltramadol and O-desmethyltramadol) was developed using chemical modification and liquid chromatography-high-resolution tandem mass spectrometry (LC-HR-MS/MS) with Orbitrap technology. After chemical derivatization, each of the investigated T series exhibited informative mass spectra that enabled better exposition of their structures. The developed method was successfully implemented to explicitly identify the structures of tramadol and its N-desmethyltramadol metabolite in urine samples at low ng/mL levels. An efficient derivatization-aided strategy was developed for rapidly elucidating the structure of tramadol-like compounds. The method is intended to assist forensic chemists in better diagnosing T and its analogs and metabolites in clinical or forensic toxicology laboratories.

New palladium(II) β-ketoesterates for focused electron beam induced deposition: synthesis, structures, and characterization.

We report the synthesis and characterization of new palladium(II) β-ketoesterate complexes [Pd(CH3COCHCO2R)2] with alkyl substituents R = tBu, iPr, Et. These compounds can have potential use in focused electron beam induced deposition (FEBID), which is a direct write method for the growth of structures at the nanoscale. However, it is still a major challenge to obtain deposits with a high metal content, and new precursor molecules are needed to overcome this. Single crystal X-ray diffraction, infrared spectroscopy, nuclear magnetic resonance spectroscopy, and density-functional theory calculations were used to confirm the compounds' composition and structure. Using thermal analysis and sublimation experiments, we investigate their thermal stability and volatility. These studies show that the palladium complexes sublimate over the range 348-353 K under 10-2 mbar pressure. The electron-induced decomposition of the complex molecules in the gas phase and their thin layers on silicon substrates were analysed using electron impact mass spectrometry (EI MS) and microscopy studies (SEM/EDX). They confirm that the precursor electron-induced fragmentation depends on the molecular structure. The obtained results reveal that [Pd(CH3COCHCO2tBu)2] with cis-positioned tert-butyl groups may be a promising FEBID precursor, and we carried out preliminary deposition experiments using this compound.

Synthesis, biological evaluation and in silico molecular modelling studies of chloro substituted bis-indole containing benzohydrazide analogues as potential anti-diabetic and anti-Alzheimer's agents

Fifteen bis-indolylmethane analogues were synthesized, characterized through NMR (1H, 13C) and high-resolution electron-impact mass spectrometry (HREI-MS), and tested against α-glucosidase, α-amylase, acetylcholinesterase, and butyrylcholinesterase inhibitory potentials. All analogues exhibited different inhibitory potentials, with IC50 values ranging between 7.5 ± 0.92 to 58.4 ± 0.07 μM (α-glucosidase), and 0.80 ± 0.05 to 15.30 ± 0.10 μM (α-amylase) as compared to the standard drug acarbose (IC50 = 38.45 ± 0.80 and 8.90 ± 0.10 μM). Out of fifteen analogues, nine showed an excellent inhibitory potency that was manyfold better than standard drugs. A slight increase or decrease in inhibition was observed due to substituents attached at imine site. In the case of α-amylase inhibition, two analogues such as 2 and 11, showed excellent inhibitory potential with IC50 values of 0.80 ± 0.05 and 0.90 ± 0.10 μM while all other analogues showed good potency. All analogues were also tested against acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) inhibitory potentials, and they showed good potentials ranging from 1.40 ± 0.20 to 16.20 ± 0.50 μM (AChE) and 3.20 ± 0.10 to 19.60 ± 0.20 μM (BuChE) as compared to the standard drug Donepezil (IC50 = 2.16 ± 0.12 μM and 4.5 ± 0.11 μM). In the case of AChE, analogue 3 is the most potent, and in the case of BuChE, analogue 9 is the most potent among the series. The structure-activity relationship was carried out, mainly associated with the nature, number, and position and the electron-donating and electron-withdrawing effects of the substituent(s) on the phenyl ring. The binding modes as well as binding free energy for α-glucosidase and α-amylase inhibitors were determined through docking studies.

A facile synthesis of iron oxide nanoparticles as a nano-sensor to detect levofloxacin and ciprofloxacin in human blood and evaluation of their biological activities.

A rapid synthesis of a pH-stable magnetic nano-sensor (iron oxide nanoparticles, Fe-NPs, ∼2.6 nm) encapsulated with 3-aminobenzoic acid (3-ABA) was achieved. 3-ABA was prepared for the first time through the reduction of 3-nitrobenzoic acid (3-NBA) in the presence of HCl and tin. Electron-impact mass spectrometry (EIMS), Fourier-transform infrared (FTIR), nuclear magnetic resonance (NMR), ultraviolet visible (UV) spectroscopy and atomic force microscopy (AFM) were used for characterization. Ten drugs, namely, ciprofloxacin (CPF), levocetirizine (LCT), levofloxacin (LVF), sulbactam sodium (SBS), ephedrine (EPH), thymine (THM), sertraline (SRT), pyridoxine (PRX), cefotaxime (CFX) and ceftriaxone (CFT) were screened with Fe-NPs. A pronounced hypsochromic shift was observed for levofloxacin and ciprofloxacin, proving that 3-ABA-coated Fe-NPs were an efficient nano-sensor for levofloxacin and ciprofloxacin up to the limit of 0.5 and 0.7 μM, respectively. The stoichiometry of the complexes was conclusively determined as 1 : 1 using Job's plot analysis. Furthermore, the drugs were successfully detected in real samples, including tap water, well water, and human blood. Moreover, the antioxidant activity, urease and lipoxygenase inhibitory potential of these nanoparticles were evaluated, exhibiting promising antioxidant potential.

Self-reducing precursors for aluminium metal thin films: evaluation of stable aluminium hydrides for vapor phase aluminium deposition.

Thin films of Al as interconnect materials and those of AlN as wide bandgap semiconductor and piezoelectric material are of great interest for microelectronic applications. For the fabrication of these thin films via chemical vapor deposition (CVD) based routes, the available precursor library is rather limited, mostly comprising aluminium alkyls, chlorides, and few small amine-stabilized aluminium hydrides. Herein, we focused on rational precursor development for Al, their characterization and comparison to existing precursors comprising stabilized aluminium hydrides. We present and compare a series of potentially new and reported aluminium hydride precursors divided into three main groups with respect to their stabilization motive, and their systematic structural variation to evaluate the physicochemical properties. All compounds were comprehensively characterized by means of nuclear magnetic resonance spectroscopy (NMR), Fourier-transform infrared spectroscopy (FTIR), elemental analysis (EA), electron-impact ionization mass spectrometry (EI-MS) and thermogravimetric analysis (TGA). Promising representatives were further evaluated as potential single source precursors for aluminium metal formation in proof-of-concept experiments. Structure and reaction enthalpies with NH3 or H2 as co-reactants were calculated via first principles density functional theory simulations and show the great potential as atomic layer deposition (ALD) precursors for Al and AlN thin films.

Broccoli Leaves (Brassica oleracea var. Italica) as a Source of Bioactive Compounds and Chemical Building Blocks: Optimal Extraction Using Dynamic Maceration and Life Cycle Assessment

Bioactive compounds (BACs) and chemical building blocks (CBBs) play a pivotal role in driving economic growth. These compounds, known for their diverse applications in pharmaceuticals, agriculture, and manufacturing, have become integral to meeting the increasing demand for sustainable and innovative products. In this research, we used and characterized dynamic maceration to extract BACs and CBBs from broccoli leaves (BLs). A central composite design (CCD) was selected to evaluate the effect of temperature (from 4 °C to 70 °C), ethanol concentration (from 30% to 70% (v/v)), and exposition time (15 to 60 min) on total phenolic content (TPC) (mg of gallic acid equivalents (GAEs) per 100 g of dry biomass (db)). A confirmation experiment (CE) was performed to reproduce the optimal conditions (50 °C, 36.92 min, and 30% (v/v)) for BAC extraction. Results indicated a GAE concentration of 112.95 ± 0.92 mg/100 g db, while the statistical model predicted a value of 111.87 mg of GAEs/100 g db (error of 0.95%) with a rate constant (k) value of 0.0154 mg/g·min (R2 of 0.9894). BACs and CBBs were identified with gas chromatography–electron impact mass spectrometry detecting l-isoleucine, l-leucine, malonic acid, and succinic acid, among others. Finally, a life cycle inventory (LCI) was developed to determine global warming (GW) and water consumption (WC), among others, for 10 g of BL extract. Findings reported herein prove the sustainability of eco-friendly extraction of BACs and CBBs for the effective use of agricultural by-products.

Determining the parent and associated fragment formulae in mass spectrometry via the parent subformula graph

BackgroundIdentifying the molecular formula and fragmentation reactions of an unknown compound from its mass spectrum is crucial in areas such as natural product chemistry and metabolomics. We propose a method for identifying the correct candidate formula of an unidentified natural product from its mass spectrum. The method involves scoring the plausibility of parent candidate formulae based on a parent subformula graph (PSG), and two possible metrics relating to the number of edges in the PSG. This method is applicable to both electron-impact mass spectrometry (EI-MS) and tandem mass spectrometry (MS/MS) data. Additionally, this work introduces the two-dimensional fragmentation plot (2DFP) for visualizing PSGs.ResultsOur results suggest that incorporating information regarding the edges of the PSG results in enhanced performance in correctly identifying parent formulae, in comparison to the more well-accepted “MS/MS score”, on the 2016 Computational Assessment of Small Molecule Identification (CASMI 2016) data set (76.3 vs 58.9% correct formula identification) and the Research Centre for Toxic Compounds in the Environment (RECETOX) data set (66.2% vs 59.4% correct formula identification). In the extension of our method to identify the correct candidate formula from complex EI-MS data of semiochemicals, our method again performed better (correct formula appearing in the top 4 candidates in 20/23 vs 7/23 cases) than the MS/MS score, and enables the rapid identification of both the correct parent ion mass and the correct parent formula with minimal expert intervention.ConclusionOur method reliably identifies the correct parent formula even when the mass information is ambiguous. Furthermore, should parent formula identification be successful, the majority of associated fragment formulae can also be correctly identified. Our method can also identify the parent ion and its associated fragments in EI-MS spectra where the identity of the parent ion is unclear due to low quantities and overlapping compounds. Finally, our method does not inherently require empirical fitting of parameters or statistical learning, meaning it is easy to implement and extend upon.Scientific contributionDeveloped, implemented and tested new metrics for assessing plausibility of candidate molecular formulae obtained from HR-MS data.

Ultraviolet-Initiated Decomposition of Solid 1,1-Diamino-2,2-dinitroethylene (FOX-7).

FOX-7 (1,1-diamino-2,2-dinitroethylene) was photolyzed with 202 nm photons to probe reaction energies, leading to the decomposition of this energetic material and to compare results from irradiations using lower-energy 532 and 355 nm photons as well as higher-energy electrons. The photolysis occurred at 5 K to suppress thermal reactions, and the solid samples were monitored using Fourier transform infrared spectroscopy (FTIR), which observed carbon dioxide (CO2), carbon monoxide (CO), cyanide (CN-), and cyanate (OCN-) after irradiation. During warming to 300 K, subliming products were detected using electron-impact quadrupole mass spectrometry (EI-QMS) and photoionization time-of-flight mass spectrometry (PI-ReTOF-MS). Five products were observed in QMS: water (H2O), carbon monoxide (CO), nitric oxide (NO), carbon dioxide (CO2), and cyanogen (NCCN). The ReTOF-MS results showed overlap with electron irradiation products but also included three intermediates for the oxidation of ammonia and nitric oxide: hydroxylamine (NH2OH), nitrosamine (NH2NO), and the largest product at 76 amu with the proposed assignment of hydroxyurea (NH2C(O)NHOH). These results highlight the role of reactive oxygen intermediates and nitro-to-nitrite isomerization as key early reactions that lead to a diverse array of decomposition products.

In Silico and In Vitro Studies of 4-Hydroxycoumarin-Based Heterocyclic Enamines as Potential Anti-Tumor Agents.

The present study reports the one-step synthesis of several 3-formyl-4-hydroxycouramin-derived enamines (4a-4i) in good yields (65-94%). The characterization of the synthesized compounds was carried out via advanced analytical and spectroscopic techniques, such as melting point, electron impact mass spectrometry (EI-MS), 1H-NMR, 13C-NMR, elemental analysis, FTIR, and UV-Visible spectroscopy. The reaction conditions were optimized, and the maximum yield was obtained at 3-4 h of reflux of the reactants, using 2-butanol as a solvent. The potato disc tumor assay was used to assess Agrobacterium tumefaciens-induced tumors to evaluate the anti-tumor activities of compounds (4a-4i), using Vinblastine as a standard drug. The compound 4g showed the lowest IC50 value (1.12 ± 0.2), which is even better than standard Vinblastine (IC50 7.5 ± 0.6). For further insight into their drug actions, an in silico docking of the compounds was also carried out against the CDK-8 protein. The binding energy values of compounds were found to agree with the experimental results. The compounds 4g and 4h showed the best affinities toward protein, with a binding energy value of -6.8 kcal/mol.

GC-MS of some Amaryllidaceae alkaloids of homolycorine type.

Gas chromatography-mass spectrometry (GC-MS) is the most frequently applied technique for analysis of Amaryllidaceae alkaloids in plant extracts. These compounds, known for their potent bioactivities, are a distinctive chemotaxonomic feature of the Amaryllidoideae subfamily (Amaryllidaceae). The Amaryllidaceae alkaloids of homolycorine type with a C3-C4 double bond generally show molecular and diagnostic ions at the high mass region with low intensity in EIMS mode leading to problematic identification in complex plant extracts. Eleven standard homolycorine-type alkaloids (isolated and identified by 1D and 2D nuclear magnetic resonance) were subjected to separation with gas chromatography and studied with electron impact mass spectrometry including single quadropole (GC-EIMS), tandem (GC-EIMS/MS), and high resolution (GC-HR-EIMS) detectors, as well as with chemical ionisation mass spectrometry (GC-CIMS). Alkaloid fractions from two Hippeastrum species and Clivia miniata were subjected to GC-EIMS and GC-CIMS for alkaloid identification. GC-EIMS in combination with GC-CIMS provided significant structural information for homolycorine-type alkaloids with C3-C4 double bond facilitating their unambiguous identification. Based on the obtained typical fragmentation, other eleven homolycorine-type compounds were identified in extracts from two Hippeastrum species by parallel GC-EIMS, GC-CIMS and LC-ESI/ToF/MS and in extracts from Clivia miniata by GC-EIMS. GC-MS can be successfully applied for identification of new and known homolycorine-type alkaloids, as well as for chemotaxonomical and chemoecological studies, among others within the Amaryllidoideae subfamily.

Probing O2-dependence of tetrahydrofuranyl reactions via isomer-resolved speciation

Low-temperature oxidation of tetrahydrofuran involves competing reactions that depend on temperature, pressure, and oxygen concentration, including ring-opening and subsequent oxidation of initial radicals (R˙), HOO-elimination yielding dihydrofuran isomers, and the formation of peroxy radicals (ROO˙). The latter species, upon isomerization, lead to hydroperoxy-substituted radicals (Q˙OOH) that undergo reaction either via unimolecular decomposition or second-O2-addition. Quantitative measurements of partially oxidized intermediates formed from each type of reaction provide critical constraints that are required for accurate modeling of combustion. To examine the influence of temperature and oxygen concentration on intermediates from tetrahydrofuran, isomer-resolved speciation measurements were conducted at 810 Torr in a jet-stirred reactor (JSR) from 500 K to 1000 K. Resulting from negative-temperature coefficient behavior, species concentrations peaked at two temperatures, 600 K and 800 K, which were then selected for separate experiments to quantify O2-dependence using concentrations of 0.37 · 1018 – 7.40 · 1018 molecules cm–3.Utilizing vacuum-ultraviolet absorption spectroscopy and electron-impact mass spectrometry, several species related to R˙ + O2 reactions were quantified for the first time, including explicit resolution and quantification of constitutional isomers tetrahydrofuran-3-one, butanedial, and allyl formate; the latter two resulting from ring-opening reactions of Q˙OOH radicals. For the majority of species, including dihydrofuran isomers, tetrahydrofuran-3-one, oxirane, and methyloxirane, clear dependence on O2 exists that is not captured quantitatively by chemical kinetics mechanisms. The latter two species arise from reactions of ring-opened α-tetrahydrofuranyl radicals while the others are derived initially from R˙ + O2 reactions. The experiments herein provide new targets for refinement of chemical kinetics mechanisms of tetrahydrofuran. The discrepancies existing between the measured and model-predicted species profiles indicate that sub-mechanisms for important intermediates may require additional elementary reactions, such as for dihydrofuran isomers. In addition, rates for O2-addition to tetrahydrofuranyl radicals in chemical kinetics mechanisms, which employ rate rules from alkyl radicals, merit scrutiny.

Para-Substituted Thiosemicarbazones as Cholinesterase Inhibitors: Synthesis, In Vitro Biological Evaluation, and In Silico Study.

The current research reports the synthesis of 14 para-substituted thiosemicarbazone derivatives in good to excellent yields using standard procedures. Initially, 4-ethoxybenzaldehyde (1) and 4-nitrobenzaldehyde (2) were refluxed with thiosemicarbazide in the presence of acetic acid in ethanol for 4-5 h. Then, various substituted phenacyl bromides were treated with the desired thiosemicarbazones (3 and 4) in the presence of triethylamine in ethanol with constant stirring for 5-6 h. The resulting derivatives were confirmed through electron impact mass spectrometry and 1H NMR spectroscopy and evaluated for anticholinesterase inhibitory activity. Among the series, four compounds, 19, 17, 7, and 6, showed potent inhibitory activity against the acetylcholinesterase (AChE) enzyme, having IC50 values of 110.19 ± 2.32, 114.57 ± 0.15, 140.52 ± 0.11, and 160.04 ± 0.02 μM, respectively, compared with standard galantamine (IC50 = 104.5 ± 1.20 μM). Similarly, compounds 19 (IC50 = 145.11 ± 1.03 μM), 9 (IC50 = 147.20 ± 0.09 μM), 17 (IC50 = 150.36 ± 0.18 μM), and 6 (IC50 = 190.21 ± 0.13 μM) were the most excellent inhibitors of butyrylcholinesterase (BChE) when compared with the standard drug galantamine (IC50 = 156.8 ± 1.50 μM). In silico studies were accomplished on the produced derivatives in order to explain the binding interface of compounds with the active sites of AChE and BChE enzymes.

An efficient synthesis of O- and N- alkyl derivatives of 4-aminobenzoic acid and evaluation of their anticancer properties

A series of twenty alkyl derivatives (2–21) of 4-amino benzoic acid (1, PABA) have been prepared using potassium carbonate and opportune alkylating agents under simple and mild reaction conditions. Compounds (16–21) are reported for the first time. Electron impact mass spectrometry (EIMS), Fourier transform infrared (FTIR) and Proton nuclear magnetic resonance (1H-NMR) spectroscopic techniques were adopted for the characterization of these analogues. In the present study, the cytotoxic screening of sixteen compounds (3, 5–11, 13 and 15–21) was also achieved against lung (NCI-H460) and oral squamous carcinoma (CAL-27) cell lines. Compound 20 has shown magnificent inhibitory properties against NCI-H460 cell line (IC50 15.59 and 20.04 µM, respectively) at a lower dose than that of the control (cisplatin; IC50 21.00 µM). One-way analysis of variance (ANOVA), t-test and Pearson correlation coefficient (PCC) have been performed to determine the reliability of current data through statistical package for the social sciences (SPSS).

In silico studies and antimicrobial investigation of synthesised novel N-acylhydrazone derivatives of indole

Indole is an exceptional scaffold in the discovery and design of drugs with different mechanisms and biological activity. Numerous research has been conducted on N-acylhydrazones of indole and its derivatives, however, no account of the synthesis, molecular docking and the antimicrobial activities of the eleven synthesised compounds has never been reported. The study was therefore designed to synthesize, characterize, carry out molecular docking and determine the antimicrobial activities of novel N-acylhydrazone derivatives of indole.Aldol condensation of synthesised hydrazides with aromatic aldehydes led to the formation of the N-acylhydrazone derivatives of indole. The structure of the compounds were confirmed by proton nuclear magnetic Resonance (1H NMR) and electron impact mass spectrometry (EIMS). The N-acylhydrazones were screened against ten microbes (four fungi three Gram-positive bacteria, and three Gram-negative bacteria) at concentrations of 100 to 6.26 mg/mL, using agar well diffusion and fungi carpeted antimicrobial assays. Gentamicin (5 mg/mL) was the positive control for bacteria while tioconazole (70%) was used for fungi. The molecular docking studies was done and the docking scores recorded accordingly on four antimicrobial receptors with PDB codes (3CR7, 3FHV, 6L1L and 6SPC).The synthesised compounds displayed moderate activity against the test organisms with the zone of inhibitions range 24 ± 0.00 to 18 ± 0.70 mm at 100 mg/mL as compared to the standards (gentamicin 10 µg/mL (36 ± 1.41), tioconazole 70% (26 ± 4.24)). All synthesised N-acylhydrazone derivatives exhibited a good number of hydrophobic interactions, classical and non-classical hydrogen bonding with the docked protein enzymes. Compound 10 and 1 were predicted to exhibit highest binding energy of -9.7 and -9.2 kcal/mole respectively with the binding site of 6SPC. Other compounds were found to have higher predicted binding energies than the standard drugs. Previously, there has been no report on the synthesis of N-acylhydrazone derivatives of Indole used in this study, their molecular docking and antimicrobial analyses is being reported for the first time. Since microbial resistance poses a major threat to human health globally, this research screened the synthesised compounds on fungi and bacteria and were found to be active against the selected microbes. These compounds if ameliorated, will reduce the uncontrollable rise in the multidrug-resistant (MDR) bacteria in Africa and in the universe.Therefore, since the synthesised N-acylhydrazone derivatives have potential in inhibiting microbial growth and showed good binding parameters with the tested enzymes, they could be effectively developed into antimicrobial agents useful for treating a wide range of microbial infections. Further research should conducted on the drugability, toxicity, minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) of the drug compounds.

Probing O2 dependence of hydroperoxy-butyl reactions via isomer-resolved speciation

Degenerate chain-branching mechanisms of n-alkanes are centered on the formation of hydroperoxy-alkyl radicals (̇QOOH), formed via ̇R + O2 reactions, and the ensuing competition between unimolecular decomposition and second-O2-addition. Quantitative measurements of partially oxidized intermediates formed via reactions of ̇QOOH provide critical constraints that are required for accurate modeling of combustion chemistry. To examine the influence of temperature and oxygen concentration on intermediates from unimolecular decomposition of ̇QOOH, isomer-resolved speciation measurements were conducted on n-butane oxidation at 835 Torr in a jet-stirred reactor (JSR) from 500 – 900 K. Resulting from negative-temperature coefficient behavior, cyclic ether formation peaked at two temperatures, 650 K and 800 K, which were selected for separate experiments to quantify the O2-dependence of species profiles using O2 concentrations of 4.2 · 1017 – 1.1 · 1019 molecules cm–3.Utilizing vacuum-ultraviolet absorption spectroscopy and electron-impact mass spectrometry, cyclic ether isomers were quantified separately, including explicit resolution of cis- and trans- isomers of 2,3-dimethyloxirane. Stereoisomers of 2-butene were also quantified explicitly. For all cyclic ethers, a common trend in O2-dependence emerged: species concentrations reach a maximum near 3.0 · 1018 molecules cm–3 (equivalence ratio of 0.5). Although quantitative disparities are evident, chemical kinetics modeling qualitatively reproduces the O2 dependence of species at 650 K. However, at 800 K, weak dependence on O2 is predicted, which is in contrast with the measurements. Two carbonyls, diacetyl and methyl vinyl ketone, were also quantified and follow similar dependence on [O2] and temperature as the cyclic ethers, which indicates some fraction forms via ̇QOOH-mediated reactions. The discrepancies between the measured and model-predicted species profiles indicate that sub-mechanisms for important intermediates may require additional elementary reactions, including stereochemical-specific reactions, to improve the fidelity of n-alkane combustion modeling.

Silver ionic compounds as a source of metal carriers in the gas phase

In the present study, we have synthesised and characterised new silver(I) complexes with the general formula [Ag(NH2tBu)2](RfCO2)·xH2O, where Rf = CF3, x = 0.5; Rf = C2F5, C5F11, C6F13, x = 0; and [Ag(NH2tBu)2][Ag(NH2tBu)2(H2O)](RfCO2)2·xH2O, where Rf = C3F7, x = 0.25; Rf = C4F9, x = 0. Single crystal X-ray diffraction, infrared spectroscopy (IR) and nuclear magnetic resonance (NMR) spectroscopy were used to confirm compounds’ composition and structure. The volatility of the compounds was studied using thermal analysis, electron impact (EI) mass spectrometry, variable temperature infrared spectroscopy, and sublimation experiments. Research has revealed that when compounds are heated, their structures are changed, and volatile silver carboxylates are formed. A thermal decomposition mechanism over reduced pressure was proposed. Two compounds [Ag(NH2tBu)2](CF3CO2)·0.5H2O and [Ag(NH2tBu)2](C2F5CO2) were used in chemical vapour deposition experiments with an evaporation temperature of 473 K and a decomposition temperature in the range of 593–653 K without the using of additional reducing agents such as hydrogen. Due to the low efficiency of generating volatile metal carriers, very thin deposits containing silver were obtained.

Crannenols A-D, Sesquiterpenoids from the Irish Deep-Sea Soft Coral Acanella arbuscula.

Four undescribed sesquiterpenoids, crannenols A-D (1-4), have been isolated from CHCl2 and MeOH extracts of the deep-sea bamboo coral Acanella arbuscula. The corals were collected from a submarine canyon on the edge of Ireland's Porcupine Bank via a remotely operated vehicle. The structure elucidation of these (Z,E)-α-farnesene derivatives was achieved using a combination of 1D and 2D NMR, electron impact (1, 2), and electrospray ionization (3, 4) mass spectrometry.