Antibacterial activities, DFT and QSAR studies of quinazolinone compounds

Abstract

ABSTRACT. The quinazolinone compounds (1 and 2) in this work were examined for their in vitro antibacterial activities against gram-positive (Staphylococcus aureus) and gram-negative bacteria (Klebsiella pneumonia, Proteus bacilli and Shigella flexneri). Compared to the reference antibiotic chloramphenicol, these compounds showed high antibacterial activities against studied strains with inhibition zones observation. The ground state geometries have been optimized by using density functional theory (DFT) at B3LYP/6-31G* level of theory. The absorption spectra have been calculated by using time dependent density functional theory (TDDFT) with and without solvent. The effect of different functionals (B3LYP, MPW1PW91, and PBE1PBE) on the absorption wavelengths has been studied. The ionization potential (IP), electron affinity (EA), energy gap (Egap), electronegativity (χ), hardness (η), electrophilicity (ω), softness (S) and electrophilicity index (ωi) were computed and discussed. The nonlinear optical (NLO) properties vary by changing the theory (DFT to HF) or functional (B3LYP to CAM-B3LYP). The physicochemical parameters have been studied by quantitative structure-activity relationship (QSAR). The computed properties of investigated compounds have been compared with the Chloramphenicol as well as available experimental data.

Vibrational investigation on pharmaceutical activity of m-xylene-4-sulphonic acid by quantum computational and experimental support

“…The ionization potential was found to be 4.284 which is very huge and enough to sustain the chemical-bond stability. Generally, chemical hardness is a measure of resistance to charge transfer while electronegativity is a measure of the tendency to attract electrons by an atom in a chemical bond [43]. Here, the values of both parameters were found to be 2.421 and 6.706 respectively and they appeared in an elevated phase which showed the present compound to be a good reactive molecule for further additive properties.…”

Vibrational and NMR Investigation on Pharmaceutical Activity of 2,5- Dimethoxy-4-Ethylamphetamine by Theoretical and Experimental Support

“…The ionization potential was found to be 0.11 which is very small and was main reason for the low dipole moment and it was enough to maintain the chemical bond stability. Generally, the chemical hardness is a scale of obstacle for transformation of charge whereas the electronegativity is measure of the tendency to attract electrons by inter-chemical bond [39]. Here, both parameters were found to be 2.66 which was moderate and illustrated the good reactive character and it was not possible to add further additive drug properties.…”

“…In this venture, the donor and acceptors of electronic orbitals were identified and their energy transitions were tabulated in Table 9. Usually, the electron density delocalized among occupied Lewis type (bond or lone pair) orbitals and unoccupied (anti-bonding and Rydberg) non-Lewis orbital in order to stabilize donor acceptor interaction [39]. Here, in ring system, the transition from C1-C2 to C3-C4 and C5-C6 and they assigned to σ-σ* in which 19.39 kcal/mol energy was transferred from first chain to second chain in order to connect the major ligand groups.…”

A Convenient Synthesis of Pyrazole‐imidazoline Derivatives by Microwave Irradiation

“…Pyrazole is a five-membered heterocycle ring widely found in a large variety of compounds that possess important biological activities, such as antileishmanial, analgesic, anti-inflammatory, antibacterial, antifungal, antitumoral, and antiviral [1][2][3][4][5][6]. Because of the wide range of applications involving compounds containing pyrazole moiety, many publications concerning methodologies to obtain this heterocycle have been reported [7][8][9].…”