Combined experimental and theoretical studies of the structure-antiradical activity relationship of heterocyclic hydrazone compounds

Synthesis, DFT Study, and In Vitro Evaluation of Antioxidant Properties and Cytotoxic and Cytoprotective Effects of New Hydrazones on SH-SY5Y Neuroblastoma Cell Lines

A series of ten new hydrazide-hydrazone derivatives bearing a pyrrole ring were synthesized and structurally elucidated through appropriate spectral characteristics. The target hydrazones were assessed for radical scavenging activity through 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) tests, with ethyl 5-(4-bromophenyl)-1-(2-(2-(4-hydroxy-3,5-dimethoxybenzylidene)hydrazine-yl)-2-oxoethyl)-2-methyl-1H-pyrrole-3-carboxylate (7d) and ethyl 5-(4-bromophenyl)-1-(3-(2-(4-hydroxy-3,5-dimethoxybenzylidene) hydra zine-yl)-3-oxopropyl)-2-methyl-1H-pyrrole-3-carboxylate (8d) highlighted as the best radical scavengers from the series. Additional density functional theory (DFT) studies have indicated that the best radical scavenging ligands in the newly synthesized molecules are stable, do not decompose into elements, are less polarizable, and with a hard nature. The energy of the highest occupied molecular orbital (HOMO) revealed that both compounds possess good electron donation capacities. Overall, 7d and 8d can readily scavenge free radicals in biological systems via the donation of hydrogen atoms and single electron transfer. The performed in vitro assessment of the compound's protective activity on the H2O2-induced oxidative stress model on human neuroblastoma cell line SH-SY5Y determined 7d as the most perspective representative with the lowest cellular toxicity and the highest protection.

Thermal Decomposition Path-Studied by the Simultaneous Thermogravimetry Coupled with Fourier Transform Infrared Spectroscopy and Quadrupole Mass Spectrometry-Of Imidazoline/Dimethyl Succinate Hybrids and Their Biological Characterization

The thermal decomposition path of synthetically and pharmacologically useful hybrid materials was analyzed in inert and oxidizing conditions for the first time and presented in this article. All the imidazoline/dimethyl succinate hybrids (1-5) were studied using the simultaneous thermogravimetry (TG) coupled with Fourier transform infrared spectroscopy (FTIR) and quadrupole mass spectrometry (QMS). It was found that the tested compounds were thermally stable up to 200-208 °C (inert conditions) and up to 191-197 °C (oxidizing conditions). In both furnace atmospheres, their decomposition paths were multi-step processes. At least two major stages (inert conditions) and three major stages (oxidizing conditions) of their decomposition were observed. The first decomposition stage occurred between T_5% and 230-237 °C. It was connected with the breaking of one ester bond. This led to the emission of one methanol molecule and the formation of radicals capable of further radical reactions in both used atmospheres. At the second decomposition stage (T_max2) between 230-237 °C and 370 °C (inert conditions), or at about 360 °C (oxidizing conditions), the cleavage of the second ester bond and N-N and C-C bonds led to the emission of CH₃OH, HCN, N₂, and CO₂ and other radical fragments that reacted with each other to form clusters and large clusters. Heating the tested compounds to a temperature of about 490 °C resulted in the emission of NH₃, HCN, HNCO, aromatic amines, carbonyl fragments, and the residue (T_max2a) in both atmospheres. In oxidizing conditions, the oxidation of the formed residues (T_max3) was related to the production of CO₂, CO, and H₂O. These studies confirmed the same radical decomposition mechanism of the tested compounds both in inert and oxidizing conditions. The antitumor activities and toxicities to normal cells of the imidazoline/dimethyl succinate hybrids were also evaluated. As a result, the two hybrid materials (3 and 5) proved to be the most selective in biological studies, and therefore, they should be utilized in further, more extended in vivo investigations.

Structure-activity relationship of antioxidant prenylated (iso)flavonoid-type compounds: quantum chemistry and molecular docking studies

Prenylated (iso)flavonoid-type compounds are a subclass of natural flavonoids that have been reported to exhibit good antioxidant properties. In the present paper, the structure-activity relationship of three typical prenylated (iso)flavonoids namely 8-prenyldaidzein (Per), Licoflavone (Lic), and erysubin F (Ery) have been determined using DFT (density functional theory)-based calculations and molecular docking studies. As result, the CH bond of the prenyl substituent was found to be the most thermodynamically favorable site for trapping free radicals in the gas phase and lipid physiological environments. While the OH bond of the B-ring seems to be more reactive in water. HAT (hydrogen atom transfer) and SPLET (sequential proton loss electron transfer) play a decisive role in the antiradical activity of the studied compounds in lipid and polar physiological environments, respectively. All of the studied compounds exhibit strong binding affinity to both xanthine oxidase and inducible nitric oxide synthase enzymes by forming several hydrogen bonds and hydrophobic interactions with their respective catalytic sites. These results suggest that (iso)flavonoid-type compounds are promising radical scavengers and antioxidants. Communicated by Ramaswamy H. Sarma.

Quantum mechanical, virtual screening, molecular docking, molecular dynamics, ADME and antimicrobial activity studies of some new indole-hydrazone derivatives as potent agents against E. faecalis

In this study, a new series of indole-5-carbaldehyde hydrazone derivative compounds were designed, synthesized, and their antimicrobial activities were determined by the microdilution method, and the in vitro cytotoxic effects on Beas-2b cell lines were investigated by MTT assay. When the activity results were examined, 5i12 showed promising activity against E. faecalis with MIC: 2 µg/mL compared to ampicillin, gentamicin, and vancomycin, although the antimicrobial activities of the indole derivatives were generally weaker than those of the standard drugs. Compounds showed no cytotoxic activity on the A549, MCF-7, and Beas-2b cell lines. Molecular docking studies were performed on 15 different proteins to understand the mechanism of 5i12's good antimicrobial action against E. faecalis, and it was concluded that the compounds interacted with FabH, not enough other protein structures. Molecular dynamics simulations were performed to investigate the protein-ligand stability of the most active compound against E. faecalis. The RMSD value of 5i12 varied between 0.02 and 0.16 nm during the MD simulation. The apoprotein peaked at 0.55 nm at the beginning of the simulation and stabilized below 0.5 nm. The theoretical ADME profiles of all compounds were calculated and found to comply with Lipinski and other limiting rules. In addition, some theoretical quantum parameters (HOMO-LUMO) of compounds, and both MEP analysis and geometric optimization analysis for 5i12 were calculated using the 6-311 G (d,p) base set and DFT/B3LYP theory, and the results were visualized. Communicated by Ramaswamy H. Sarma.