Synthesis, spectroscopic characterization, density functional theory study, antimicrobial and antioxidant activities of curcumin and alanine-curcumin Schiff base

In this work, a novel Schiff-base derived from curcumin and L-Alanine was synthesized under microwave conditions in excellent yield. The structural characterization has been carried out from their elemental analyses, FTIR, UV-Vis and 13C-NMR and 1H-NMR spectral techniques. The Schiff base (Cur-Ala) and curcumin (Cur) have been screened for their antimicrobial activity toward some pathogens clinically important microorganisms: Bacillus subtilis, Escherichia coli and Staphylococcus aureus, Aspergillus niger and Candida albicans. Result found that the Schiff base was more active than the curcumin. The antibacterial and antifungal activities of Cur-Ala can be attributed to its greatest dipole moment, as shown by theoretical calculations. Also, the antioxidant activity of Schiff base and curcumin were studied by DPPH, cupric ion reducing antioxidant capacity and o-phenanthroline techniques. Results indicate that Cur-Ala and Cur show more antioxidant activities than the standard antioxidants (BHT and BHA). Quantum chemical parameter calculations of Cur-Ala and Cur have been investigated by DFT using B3LYP/6-31G (d,p) basis set method to calculate the optimized structure, atomic charges, MESP, global reactivity descriptors and thermomolecular proprieties of both molecules.Communicated by Ramaswamy H. Sarma.

Synthesis and crystal structures of two 1H-benzo[d]imidazole derivatives: DFT and anticorrosion studies, and Hirshfeld surface analysis

The title benzimidazole compounds, namely, 2-(4-methoxynaphthalen-1-yl)-1H-benzo[d]imidazole, C₁₈H₁₄N₂O (I) and 2-(4-methoxynaphthalen-1-yl)-1-[(4-methoxynaphthalen-1-yl)methyl]-1H-benzo[d]imidazole ethanol monosolvate, C₃₀H₂₄N₂O₂·C₂H₆O (II), were synthesized by the condensation reaction of benzene-1,2-diamine with 4-methoxynaphthalene-1-carbaldehyde in the ratios 1:1 and 1:2, respectively. In I, the mean plane of the naphthalene ring system is inclined to that of the benzimidazole ring by 39.22 (8)°, while in II, the corresponding dihedral angle is 64.76 (6)°. This difference is probably influenced by the position of the second naphthalene ring system in II; it is inclined to the benzimidazole ring mean plane by 77.68 (6)°. The two naphthalene ring systems in II are inclined to one another by 75.58 (6)°. In the crystal of I, molecules are linked by N-H...N hydrogen bonds to form chains propagating along the a-axis direction. Inversion-related molecules are also linked by a C-H...π interaction linking the chains to form layers lying parallel to the ac plane. In the crystal of II, the disordered ethanol molecule is linked to the molecule of II by an O-H...N hydrogen bond. There are a number of C-H...π interactions present, both intra- and intermolecular. Molecules related by an inversion centre are linked by C-H...π interactions, forming a dimer. The dimers are linked by further C-H...π interactions, forming ribbons propagating along the b-axis direction. The interatomic contacts in the crystal structures of both compounds were explored using Hirshfeld surface analysis. The molecular structures of I and II were determined by density functional theory (DFT) calculations at the M062X/6-311+g(d) level of theory and compared with the experimentally determined molecular structures in the solid state. Local and global reactivity descriptors were computed to predict the reactivity of the title compounds. Both compounds were shown to exhibit significant anticorrosion properties with respect to iron and copper.

Biomimetic Hydroxyapatite Crystals Growth on Phosphorylated Chitosan Films by In Vitro Mineralization Used as Dental Substitute Materials

Chitosan (CS) films exhibit great potential as a substrate for the in vitro mineralization process. In this study, to mimic the formation of nanohydroxyapatite (HAP) as natural tissue, CS films coated with a porous calcium phosphate were investigated using scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDX), Fourier transforms infrared spectroscopy (FTIR), X-ray diffractometry (XRD) and X-ray photoelectron spectroscopy (XPS). Calcium phosphate coating deposited on phosphorylated derivatives of CS was obtained by a process based on phosphorylation, Ca(OH)₂ treatment and artificial saliva solution (ASS) immersion. The phosphorylated CS films (PCS) were obtained by partial hydrolysis of the PO₄ functionalities. It was demonstrated that this precursor phase could induce the growth and the nucleation of the porous calcium phosphate coating when immersed in ASS. Moreover, oriented crystals and qualitative control of calcium phosphate phases on CS matrices are obtained in a biomimetic mode. Furthermore, in vitro antimicrobial activity of PCS was evaluated against three species of oral bacteria and fungi. It revealed an increase in antimicrobial activity with minimum inhibition concentration (MIC) values of 0.10% (Candida albicans), 0.05% (Staphylococcus aureus) and 0.025% (Escherichia coli) which proves their possible use as dental substitute materials.

Synthesis, characterization, DFT, antioxidant, antibacterial, pharmacokinetics and inhibition of SARS-CoV-2 main protease of some heterocyclic hydrazones

Three hydrazone derivatives have been synthesized using condensation reaction of 4-hydrazinylbenzoic acid with three aromatic aldehydes namely: thiophene-2-carbaldehyde, thiophene-3-carbaldehyde and 2-furaldehyde in ethanol at 78 °C reflux. The synthesized molecules have been characterized using spectroscopic and physicochemical methods including UV-Vis, IR, ¹H NMR, ¹³C NMR, ¹⁵N NMR and melting point determination. Optimized molecular structures, UV-Vis and IR spectra modeling, the reactivity, the stability and some quantum chemical parameters of the synthesized molecules were modeled utilizing density functional theory (DFT). The obtained theoretical results were found in good agreement with the experimental results. On the other hand, the antioxidant and antibacterial activities of the molecules under study were evaluated to better understand the associated mechanisms of action specifically. Also, predicted ADME-T and pharmacokinetic parameters indicated that these compounds showed good oral bioavailability. Finally, molecular docking has been used to predict the inhibitory activity of the studied hydrazone derivatives on the SARS-CoV-2 main protease (Mpro).

Bacterial behaviour in the biodegradation of phenol by indigenous bacteria immobilized in Ca-alginate beads

The phenol biodegradation by Ca-alginate immobilized indigenous bacteria was performed in batch system. The effects of some operational parameters were evaluated, including % weight of alginate, calcium and CaCl₂, diameter of spheres; jellification time; solution concentration; adaptation concentration and alginate/cells ratio. The optimal biodegradation conditions were found for 2% and 3% of weight for respectively the sodium alginate and calcium chloride. The hardening time was 30  min and beads diameter of 4 cm. The degradation efficiency of the immobilized strains in these conditions exceeds 800 mg·L^-1. The results show that the mass transfer flow (nutritional intake) which depends on the concentration gradient (dC/dz), the physical-chemical properties of alginate beads through the diffusivity coefficient (D), govern the bacterial kinetics and the spatial and temporal behaviour of bacteria.

The dynamic adsorption characteristics of phenol by granular activated carbon

The objective of the present work is to determine the operating conditions of an activated carbon filter, based on the characteristics of breakthrough curves. For this we apply the technical developed by Mickaels for the ionic exchange and applied by Luchkis for the adsorption, and which is the mass transfer zone. To reach our goal, an evaluation of the operating conditions (height of the bed, flow and concentration of effluent) on the characteristics of the mass transfer zone was made and an explanation of the mechanism of adsorption was given. Thereafter a modeling of the experimental results was done.

Determination of the adsorption capacity of activated carbon made from coffee grounds by chemical activation with ZnCl2 and H3PO4

In order to evaluate the adsorptive capacities of granular activated carbon produced from coffee grounds by chemical activation, the adsorption of different phenols and acid and basic dyes, has been carried out. The comparison with a commercial activated carbon has been made. Adsorption isotherms of phenols and dyes (acid and basic) onto produced and commercial granular activated carbons were experimentally determined by batch tests. Both Freundlich and Langmuir models are well suited to fit the adsorption isotherm data. As a result, the coffee grounds based activated carbon may be promising for phenol and dye removal from aqueous streams.