In vitro antibacterial and time-kill assay of ethanolic extract of Davilla nitida bark on multidrug resistant bacteria isolated from diabetic foot lesions

This study reported the antimicrobial activity of the bark extract of Davilla nitida on multidrug resistant bacteria isolated from Diabetic Foot Infections. Antibacterial activity of the bark extract was evaluated by agar Disk-Diffusion (DD), Broth Dilution (BD), Checkerboard and Time-kill methods. The extract showed a significant antibacterial activity against all groups of bacteria tested. BD was more sensitive for determining the antibacterial activity of the bark extract than the DD method. The bark extract inhibited the growth of bacteria with high-levels of antibiotic-resistance, such as Pseudomonas spp. (100.0%), Enterobacer spp. (88.89%), Staphylococcus aureus (54.55%), Streptococcus pneumoniae (75.0%), Staphylococcus saprophyticus (92.86%). The combination of extract with antibiotics resulted in an additive effect against most of the strains tested. Time-kill kinetics profiles of bark extract showed bactericidal and time-dependent properties. Our results suggest that the bark extract of Davilla nitida is a source of bioactive compounds, which may be useful against antibiotic-resistant bacteria.     

A combined experimental and theoretical approach for radical-scavenging activity of edaravone and its related derivatives

The experimental and theoretical study for evaluation of scavenging activity of edaravone (S1) and related derivatives, such as antipyrine (S2), dipyrone (S3), and phenylbutazone (S4), was carried out against DPPH and ABTS radicals. Structure–activity relationship study was performed using quantum chemical calculations at the DFT/B3LYP level of theory along with the 6-31G* basis sets. S1 and S4 are more effective scavengers against DPPH and ABTS. We observed little effects of S2 and S3 at several concentrations against these two free radicals. The calculations of HOMO, ionization potential, and bond dissociation energy confirmed that a hydrogen transfer is more preferential than an electron transfer. The radical stability of these compounds is related with spin densities. In accordance with experimental and theoretical results, edaravone is more active than phenylbutazone as scavenging drug.     

Molecular dynamics simulation of the electron ionization mass spectrum of tabun

Tabun (ethyl N,N‐dimethylphosphoramidocyanidate), or GA, is a chemical warfare nerve agent produced during the World War II. The synthesis of its analogs is rather simple; thus, it is a significant threat. Furthermore, experiments with tabun and other nerve agents are greatly limited by the involved life risks and the severe restrictions imposed by the Chemical Weapons Convention. For these reasons, accurate theoretical assignment of fragmentation pathways can be especially important. In this work, we employ the Quantum Chemistry Electron Ionization Mass Spectra method, which combines molecular dynamics, quantum chemistry methods, and stochastic approaches, to accurately investigate the electron ionization/mass spectrometry (EI/MS) fragmentation spectrum and pathways of the tabun molecule. We found that different rearrangement reactions occur including a McLafferty involving the nitrile group. An essential and characteristic pathway for identification of tabun and analogs, a two‐step fragmentation producing the m/z 70 ion, was confirmed. The present results will be also useful to predict EI/MS spectrum and fragmentation pathways of other members of the tabun family, namely, the O‐alkyl/cycloalkyl N,N‐dialkyl (methyl, ethyl, isopropyl, or propyl) phosphoramidocyanidates.     

Energetic differences between the five- and six-membered ring hydrocarbons: strain energies in the parent and radical molecules

The C-H bond dissociation enthalpies (BDEs) for the five- and six-membered ring alkanes, alkenes, and dienes were investigated and discussed in terms of conventional strain energies (SEs). New determinations are reported for cyclopentane and cyclohexane by time-resolved photoacoustic calorimetry and quantum chemistry methods. The C-H BDEs for the alkenes yielding the alkyl radicals cyclopenten-4-yl and cyclohexen-4-yl and the alpha-C-H BDE in cyclopentene were also calculated. The s-homodesmotic model was used to determine SEs for both the parent molecules and the radicals. When the appropriate s-homodesmotic model is chosen, the obtained SEs are in good agreement with the ones derived from group additivity schemes. The different BDEs in the title molecules are explained by the calculated SEs in the parent molecules and their radicals: (1) BDEs leading to alkyl radicals are ca. 10 kJ mol (-1) lower in cyclopentane and cyclopentene than in cyclohexane and cyclohexene, due to a smaller eclipsing strain in the five-membered radicals relative to the parent molecules (six-membered hydrocarbons and their radicals are essentially strain free). (2) C-H BDEs in cyclopentene and cyclohexene leading to the allyl radicals are similar because cyclopenten-3-yl has almost as much strain as its parent molecule, due to a synperiplanar configuration. (3) The C-H BDE in 1,3-cyclopentadiene is 27 kJ mol (-1) higher than in 1,4-cyclohexadiene due to the stabilizing effect of the conjugated double bond in 1,3-cyclopentadiene and not to a destabilization of the cyclopentadienyl radical. The chemical insight afforded by group additivity methods in choosing the correct model for SE estimation is highlighted.     

Solid phase extraction of petroleum carboxylic acids using a functionalized alumina as stationary phase

Petroleum essentially consists of a mixture of organic compounds, mainly containing carbon and hydrogen, and, in minor quantities, compounds with nitrogen, sulphur, and oxygen. Some of these compounds, such as naphthenic acids, can cause corrosion in pipes and equipment used in processing plants. Considering that the methods of separation or clean up the target compounds in low concentrations and in complex matrix use large amounts of solvents or stationary phases, is necessary to study new methodologies that consume smaller amounts of solvent and stationary phases to identify the acid components present in complex matrix, such as crude oil samples. The proposed study aimed to recover acid compounds using the solid phase extraction method, employing different types of commercial stationary ion exchange phases (SAX and NH(2)) and new phase alumina functionalized with 1,4-bis(n-propyl)diazoniabicyclo[2.2.2]octane chloride silsesquioxane (Dab-Al(2)O(3)), synthesized in this work. Carboxylic acids were used as standard mixture in the solid phase extraction for further calculation of recovery yield. Then, the real sample (petroleum) was fractionated into saturates, aromatics, resins, and asphaltenes, and the resin fraction of petroleum (B1) was eluted through stationary ion exchange phases. The stationary phase synthesized in this work showed an efficiency of ion exchange comparable to that of the commercial stationary phases.     

Synthesis and Antitubercular Evaluation of N‐Arylpyrazine and N,N′‐Alkyl‐diylpyrazine‐2‐carboxamide Derivatives

Two series of pyrazinamide (PZA) derivatives have been synthesized and evaluated for their in vitro antibacterial activity against Mycobacterium tuberculosis H37Rv. Some compounds exhibited minimum inhibitory concentration activity of 50–100 μg/mL, greater than the first line antituberculosis drug PZA in Alamar Blue assay (>100 μg/mL). The obtained activities can be considered promising results, which characterizes these compounds as good start points to development of new antitubercular agents.     

Temperature stable supercapacitors based on ionic liquid and mixed functionalized carbon nanomaterials

The ionic liquid 1-butyl-2,3-dimethylimidazolium bis(trifluoromethylsulfonyl)imide (BDMIM-TFSI) showed a conductivity of 1.65?mS cm^?1 and an electrochemical stability window of 4.4?V at room temperature. Two types of electrodes based on carbon nanomaterials were prepared: (1) with alternating layers of two oppositely charged functionalized double-walled carbon nanotubes (DWCNTs) and (2) with the functionalized DWCNTs and graphene oxide nanoplatelets. The electrodes presented a porous morphology and a connected pathway between the carbon nanotubes and graphene oxide platelets. Electrochemical capacitors based on the carbon nanomaterials and BDMIM-TFSI were produced in a stacking configuration and were characterized at 25?°C, 60?°C, and 100?°C. The supercapacitors with electrodes based on the three alternating layers of two oppositely charged DWCNTs and graphene oxide presented higher values of capacitance, which were attributed to a morphology favorable to providing ionic access to the carbonaceous surface. Box-like voltammetric curves were used to calculate the capacitance in a 4-V potential window at 100?°C.     

Simultaneous determination of multibenzodiazepines by HPLC/UV: Investigation of liquid-liquid and solid-phase extractions in human plasma

A method for simultaneous determination of seven benzodiazepines (BZPs) (flunitrazepam, clonazepam, oxazepam, lorazepam, chlordiazepoxide, nordiazepam and diazepam using N-desalkylflurazepam as internal standard) in human plasma using liquid-liquid and solid-phase extractions followed by high-performance liquid chromatography (HPLC) is described. The analytes were separated employing a LC-18 DB column (250 mm × 4.6 mm, 5 μm) at 35 °C under isocratic conditions using 5 mM KH₂PO₄ buffer solution pH 6.0:methanol:diethyl ether (55:40:5, v/v/v) as mobile phase at a flow rate of 0.8 mL min⁻¹. UV detection was carried out at 245 nm. Employing LLE, the best conditions were achieved with double extraction of 0.5 mL plasma using ethyl acetate and Na₂HPO₄ pH 9.5 for pH adjusting. Employing SPE, the best conditions were achieved with 0.5 mL plasma plus 3 mL 0.1 M borate buffer pH 9.5, which were then passed through a C18 cartridge previously conditioned, washed for 3 times with these solvents: 3 mL 0.1 M borate buffer pH 9.5, 4 mL Milli-Q water and 1 mL acetonitrile 5%, finally the BZPs elution was carried with diethyl ether:n-hexane:methanol (50:30:20). In both methods the solvent was evaporated at 40 °C under nitrogen flow. The validation parameters obtained in LLE were linearity range of 50-1200 ng mL⁻¹ plasma (r ≥ 0.9927), limits of quantification of 50 ng mL⁻¹ plasma, within-day and between-day CV% and E% for precision and accuracy lower than 15%, and recovery above 65% for all BZPs. In SPE, the parameter obtained were linearity range of 30-1200 ng mL⁻¹ plasma (r ≥ 0.9900), limits of quantification of 30 ng mL⁻¹ plasma, within-day and between-day CV% and E% for precision and accuracy lower than 15% and recovery above 55% for all BZPs. These extracting procedures followed by HPLC analysis showed their suitable applicability in order to examine one or more BZPs in human plasma. Moreover, it could be suggested that these procedures might be employed in various analytical applications, in special for toxicological/forensic analysis.     

Multivariate optimization by exploratory analysis applied to the determination of microelements in fruit juice by inductively coupled plasma optical emission spectrometry

A method for the direct determination (without sample pre-digestion) of microelements in fruit juice by inductively coupled plasma optical emission spectrometry has been developed. The method has been optimized by a 2³ factorial design, which evaluated the plasma conditions (nebulization gas flow rate, applied power, and sample flow rate). A 1:1 diluted juice sample with 2% HNO₃ (Tetra Packed, peach flavor) and spiked with 0.5 mg L^− 1 of Al, Ba, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Sb, Sn, and Zn was employed in the optimization. The results of the factorial design were evaluated by exploratory analysis (Hierarchical Cluster Analysis, HCA, and Principal Component Analysis, PCA) to determine the optimum analytical conditions for all elements. Central point condition differentiation (0.75 L min^− 1, 1.3 kW, and 1.25 mL min^− 1) was observed for both methods, Principal Component Analysis and Hierarchical Cluster Analysis, with higher analytical signal values, suggesting that these are the optimal analytical conditions. F and t-student tests were used to compare the slopes of the calibration curves for aqueous and matrix-matched standards. No significant differences were observed at 95% confidence level. The correlation coefficient was higher than 0.99 for all the elements evaluated. The limits of quantification were: Al 253, Cu 3.6, Fe 84, Mn 0.4, Zn 71, Ni 67, Cd 69, Pb 129, Sn 206, Cr 79, Co 24, and Ba 2.1 µg L^− 1. The spiking experiments with fruit juice samples resulted in recoveries between 80 and 120%, except for Co and Sn. Al, Cd, Pb, Sn and Cr could not be quantified in any of the samples investigated. The method was applied to the determination of several elements in fruit juice samples commercialized in Brazil.     

LC‐MS identification of derivatized free fatty acids from adipocere in soil samples

Free fatty acids were derivatized as amides (DFFA) by reaction with (R)‐(+)‐1‐phenylethylamine, using a simple, fast and robust reaction scheme. A HPLC method with diode array and ESI MS detection was developed for the analysis of the derivatized substances. Six fatty acids were used in the method development: myristic, linoleic, palmitic, oleic, margaric and stearic acids. Under these conditions the elution of the DFFA are well resolved with retention times raging from 6.9 to 16.0 min. Fatty acids were extracted from cemetery soil and from adipocere formation experimental soils using a Soxhlet extraction, using as solvent ether/dichloromethane (1:1). Each DFFA is characterized by three m/z peaks: molecular weight of the substance; molecular weight of a dimer of the substance; the molecular weight of the dimer plus the atomic mass of sodium. The analysis of soil samples detected the six fatty acids used in the method developed plus palmitoleic and pentadecanoic. Beside this set of eight fatty acids other 13 fatty acids were detected in trace quantities or only in some soils and some were tentatively assigned as: 10‐hydroxystearic, myristoleic, heptadecenoic and arachidic acids.