Semiempirical studies, spectral analysis, in vitro antibacterial and DNA degradation studies of heterocyclic thiosemicarbazone ligand and its metal complexes

Insight into Tyrosine-Containing Pharmaceuticals as Potential Inhibitors of SARS-CoV-2 3CLpro and NSP16: Structural Analysis, Docking Studies, Molecular Dynamics Simulations, and Density Functional Theory Investigations

Tyrosine-containing pharmaceuticals’ (TPh) potential to inhibit SARS CoV-2 3-chymotrypsin-like proteases (3CLpro) and nonstructural protein 16 (NSP16) has been explored using docking studies, molecular dynamics simulations, and density functional theory. The TPh with FDA approval showed excellent contact with the active site pockets of 3CLpro and NSP16. Their binding affinity scores ranged from −5.8 to −4.9 kcal/mol and −6.3 to −4.8 for 3CLpro and NSP16, respectively. A 100-ns molecular dynamics simulation confirmed the stability of the carbidopa/NSP16 complex and N-acetyl tyrosine with both target enzymes. Further, the HOMO-LUMO transitions, molecular orbitals, and dipole moments of carbidopa, droxidopa, and N-acetyl tyrosine were computed using density functional theory (DFT). Considering N-acetyl tyrosine and carbidopa’s substantial inhibitory activity, it is recommended to investigate them further in order to explore their application for the treatment of COVID-19 or any other coronaviruses in the future.

Synthesis, anti-bacterial evaluation, DFT study and molecular docking as a potential 3-chymotrypsin-like protease (3CLpro) of SARS-CoV-2 inhibitors of a novel Schiff bases

New Schiff bases {N'-(phenyl(pyridin-2-yl)methylene) isonicotinohydrazide (L¹H), N¹ -(naphthalen-1-yl)-N² -(phenyl(pyridin-2-yl) methylidene) ethane-1,2-diamine (L²H), N-(6-chlorobenzo[d]thiazol-2-yl)-1-phenyl-1-(pyridin-2-yl) methanimine (L³H)}were synthesized by reaction of 2-benzoylpyridine with different amines (2-amino-6-chlorobenzothiazole, isonicotinohydrazide and N ¹-(naphthalen-1-yl)ethane-1,2-diamine) and characterized by ¹H-NMR, ¹³C-NMR, IR mass spectroscopy and elemental analysis. The compounds were assayed by the disc diffusion method for anti-bacterial against five pathogenic bacteria species (Staphylococcus aureus, Micrococcus luteus, Staphylococcus pyogenes, Bacillus subtilis, and E. coli). All prepared Schiff bases showed good activity compared to positive control (streptomycin), Moreover the L³H showed the highest activity against S. aureus, and M. luteus than the other compounds and streptomycin. In additional molecular docking studies with 3-chymotrypsin-like protease (3CLpro), the essential enzyme for SARS-CoV-2 proliferation. The rest of compounds have shown promising results as 3CLpro inhibitors interacting with the active sites of the enzymes. Finally, DFT 's estimated electrostatic molecular potential results were used to illustrate the molecular docking findings. The DFT calculations showed that L³H has the highest dipole moment and electrophilicity index. Interestingly, L²H of the largest energy gap ∆E = 2.49 eV, there are several hydrophilic interactions that could facilitate the binding with the receptors. All of these parameters could be shared to significantly affect the protein sites of binding affinity with different extent.

Palladium (II) complexes with thione and thioalkylated thiosemicarbazones: Electrochemical, antimicrobial and thermogravimetric investigations

Four methoxy substitute salicylidene thiosemicarbazones were synthesized. The reaction of both thione and thioalkylated thiosemicarbazones with PdCl₂ in ethanol yields ONS-coordinated chelate complexes with general formula [Pd(L)Cl]. The structures of eight compounds were characterized by using analytical and spectroscopic methods. Electrochemistry of the Pd(II) complexes was studied using cyclic voltammetric technique. The CVs of the complexes were quite complicate because of some oxidative responses of the ligands which proceed by forming conjugated -N=CH-, -HC=CH- and -N=CH-HC=CH- groups. Two cathodic responses attributed to one electron reduction of Pd(II)/(I) and Pd(I)/(0) were observed for the central ion coordinated with S atom of H₃C-S- group whereas only one reduction peak appeared when the Pd(II) coordinated with S atom of >C=S group of thiosemicarbazone ligand. The latter also showed an additional anodic response assigned to Pd(II)/(III) oxidation. Thermogravimetric analysis (TGA) technique was used to investigate and compare the thermal properties of the ligands and their metal complexes. In vitro antimicrobial activity of thiosemicarbazones and their complexes was evaluated against four Gram-negative bacteria, three Gram-positive bacteria, and antifungal activity against three fungi.

Synthesis and Characterization of Cobalt(III) and Copper(II) Complexes of 2-((E)-(6-Fluorobenzo[d]thiazol-2-ylimino) methyl)-4-chlorophenol: DNA Binding and Nuclease Studies—SOD and Antimicrobial Activities

A bidentate (N- and O-) imine-based ligand (L1) and its metal complexes of types [CuII(L1)2] (C1), [CuII(L1)(Phen)] (C2), [CoIII(L1)2] (C3), and [CoIII(L1)(Phen)] (C4) (L1 = 2-((E)-(6-fluorobenzo[d]thiazol-2-ylimino)methyl)-4-chlorophenol and phen = 1,10-phenanthroline) were synthesized as potential chemotherapeutic drug candidates. The prepared complexes were structurally characterized by spectral techniques (NMR, FT-IR, LC-MS, EPR, and electronic absorption), thermogravimetric analysis (TGA/DTA), magnetic moment, and CHNO elemental analysis. Spectroscopic studies suggested the distorted octahedral structure for all complexes. In vitro bioassay studies include binding and nuclease activities of the ligand and its complexes with target calf thymus- (CT-) DNA were carried out by employing UV-Vis, fluorescence spectroscopy, viscosity, and gel electrophoresis techniques. The extent of binding propensity was determined quantitatively by Kb and Ksv values which revealed a higher binding affinity for C2 and C4 as compared to C1 and C3. In addition, the scavenging superoxide anion free radical (O∙-2) activity of metal complexes was determined by nitroblue tetrazolium (NBT) light reduction assay. Molecular docking studies with DNA and SOD enzyme were also carried out on these compounds. The antimicrobial study has shown that all the compounds are potential antibacterial agents against Gram-negative bacterial strains and better antifungal agents with respect to standard drugs used.

Computational investigations of trans‑platinum(II) oxime complexes used as anticancer drug

Some platinum oxime complexes are optimized at HF/CEP-31G level which has been reported as the best level for these type complexes in the gas phase. IR spectrum is calculated and the new scale factor is derived. NMR spectrum is calculated at the same level of theory and examined in detail. Quantum chemical parameters which have been mainly used are investigated and their formulas are given in detail. Additionally, selected quantum chemical parameters of studied complexes are calculated. New theoretical IC₅₀% formulas are derived and biological activity rankings of mentioned complexes are investigated.