The aim of this work is to optimise the antibacterial activity of essential oils (EOs) from Eucalyptus camaldulensis (ECEO), Mentha pulegium (MPEO) and Rosmarinus officinalis (ROEO) plants against Salmonella spp. and Escherichia coli. The qualitative antimicrobial effect was assessed using the disc diffusion method, the broth microdilution method was used to determine the minimum inhibitory concentrations (MIC). Polynomial models were created using an augmented centroid simplex mixture design to highlight the synergy of EOs. The results show a significant antibacterial effect of ECEO and MPEO against both bacterial strains, with inhibition zones (IZs) of 13 and 12 mm respectively against E. coli, and 13 and 11 mm against Salmonella spp. The latter strain showed a MIC of 0.625% (v: v) by the ECEO, while E. coli exhibited a MIC of 0.0781% (v: v). The binary combinations of essential oils display a synergistic effect, the proportions of the optimum EOs in the mixture giving the lowest MICm were of the order of 50.51% ECEO and 49.49% ROEO against Salmonella spp. and around 50% MPEO and 50% ECEO against E. coli. These results indicate the effectiveness of binary combinations EOs against resistant bacterial strains and suggest their importance in bacterial infections treatment.
[ASAP] Exploring Endohedral Metallofullerenes for Advanced Thin-Film Device Applications toward Next-Generation Electronics
Chemistry of Materials
DOI: 10.1021/acs.chemmater.3c01192
[ASAP] Accurate Sphingolipid Quantification Reducing Fragmentation Bias by Nonlinear Models
Analytical Chemistry
DOI: 10.1021/acs.analchem.3c02445
[ASAP] Nanoarray Enabled Size-Dependent Isolation and Proteomics Profiling of Small Extracellular Vesicle Subpopulations toward Accurate Cancer Diagnosis and Prognosis
Analytical Chemistry
DOI: 10.1021/acs.analchem.3c02594
Tandem [4+2]/retro[3+2]/[3+2] cycloaddition reactions of fluorinated‐oxadiazoles with conjugated, unconjugated, cyclic, and acyclic dienes
![Tandem [4+2]/retro[3+2]/[3+2] cycloaddition reactions of fluorinated-oxadiazoles with conjugated, unconjugated, cyclic, and acyclic dienes](https://onlinelibrary.wiley.com/cms/asset/3f027ba4-f077-4f0d-afeb-b00e7ac0c307/poc4567-toc-0001-m.png)
The exclusive mechanism of tandem reactions of fluorinated-oxadiazoles with several conjugated, unconjugated, cyclic, and acyclic dienes have been elucidated. The polarity of both inter- and intra-molecular cycloaddition steps can be influenced by two factors: the nature of the heteroatom present on the diene molecule and the size of the cyclic diene. These factors play a role in determining the reactivity and electron distribution within the diene, thereby impacting the overall polarity of the cycloaddition reactions.
Abstract
The tandem reactions of 2,5-bis(trifluoromethyl)-1,3,4-oxadiazole with conjugated, unconjugated, acyclic, and cyclic dienes have been studied at the M06-2X/6-311++G(d,p) level of theory. The rate-determining step is the initial [4+2] cycloaddition in the tandem reaction of 2,5-bis(trifluoromethyl)-1,3,4-oxadiazole with acyclic, cyclic, conjugated, and unconjugated dienes, whereas the stereochemistry of the tandem adduct is determined by the [3+2] step. The exo-coupling is kinetically favored over the endo-coupling in the initial [4+2] reaction of 2,5-(bis-trifluoromethyl)-1,3,4-oxadiazole with all the considered dienes. In the retro [3+2] step (N2 extrusion), higher activation energy is required to furnish the carbonyl ylide in the reaction of 2,5-(bis-trifluoromethyl)-1,3,4-oxadiazole with conjugated and unconjugated cyclic dienes as compared with the reaction with unconjugated acyclic dienes. At the stereochemistry [3+2] step, the intermolecular addition is kinetically favored over the intramolecular addition in the [3+2] reaction of 2,5-(bis-trifluoromethyl)-1,3,4-oxadiazole with both conjugated or unconjugated cyclic dienes and unconjugated acyclic dienes. The reaction proceeds with low activation energies when conjugated and unconjugated cyclic dienes are participating, compared with those of unconjugated acyclic dienes. Overall, the tandem process proceeds via an asynchronous one-step mechanism [4+2] coupling in an exo- or endo-cycloaddition fashion, followed by a retro [3+2], which extrudes the N2, and then the stereo-determining intermolecular or intramolecular [3+2] cycloaddition step, which leads to the tandem products. The polarity of both inter- and intra-molecular cycloaddition steps can be influenced by two factors: the nature of the heteroatom present on the diene molecule and the size of the cyclic diene. These factors play a role in determining the reactivity and electron distribution within the diene, thereby impacting the overall polarity of the cycloaddition reactions.
[ASAP] Rapid and Highly Efficient Separation of i-Motif DNA Species by CE-UV and Multivariate Curve Resolution
Analytical Chemistry
DOI: 10.1021/acs.analchem.3c01730
Effect of Ligand Structure on Ethylene Oligomerization over Salicylaldehyde Imine Nickel Complexes: Experiments and Calculations
Salicylaldehyde imine nickel complexes Ni1-Ni10 containing different electron-donating and electron-withdrawing groups on benzene rings were synthesized, using ethylenediamine, salicylaldehyde derivatives with different substituents and nickel chloride hexahydrate as raw materials. Structure characterization, such as elemental analysis, Fourier transform infrared (FT-IR), nuclear magnetic resonance (NMR), ultraviolet–visible (UV–Vis), and electrospray ionization mass spectrometry (ESI-MS), confirmed that the structure of synthesized complexes was consistent with the theoretical. Salicylaldehyde imine nickel complexes exhibited good catalytic activity in ethylene oligomerization process, and complexes containing electron-donating groups on the benzene ring had higher catalytic activity than complexes containing electron-withdrawing groups on the benzene ring. With the increase of steric hindrance of phenol hydroxyl ortho-substituents, the catalytic activity decreased, as well as the catalytic selectivity toward olefins with higher carbon number. The relationship between structure and catalytic properties was further studied by density functional theory (DFT) calculations, and the possible mechanism of nickel complexes catalyzing ethylene oligomerization was proposed.
[ASAP] Novel In Situ Self-Doping Cathode Interlayer Materials with Thickness-Insensitivity for High-Efficiency Organic Solar Cells
Chemistry of Materials
DOI: 10.1021/acs.chemmater.3c01936
Solid phase extraction of Aflatoxin M1 in milk samples by graphene oxide-poly-L-lysine nanocomposite followed by HPLC
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Dual Role of TiO(acac)2 as a Reagent and an Activator/Catalyst: A Study on the Solvent Dependent Product Formation
The dual operation of a chemical species in synthetic chemistry is an intriguing and relatively unexplored phenomenon. The application of such a species is expected to reduce the use of multiple reaction partners and catalysts/activators. Herein, we report a simple and easy-to-use protocol for the twin application of TiO(acac)2, as a reagent and an activator to synthesize β-enamino ketones with amines in acetonitrile. The same early transition metal precursor when employed in N,N-dimethylformamide with the amines, resulted in the formation of the substituted amides. Both reactions were explored with various substrates to check the viability of the present protocol. Moreover, experimental studies were conducted to understand the mechanism of both reactions.