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. KEY WORDS: Antibacterial activity, Density Functional Theory, Time Dependent Density Functional Theory, Charge transfer, Quantitative structure–activity relationship Bull. Chem. Soc. Ethiop. 2016, 30(2), 307-316.DOI: http://dx.doi.org/10.4314/bcse.v30i2.15
Highlights
The quinazolinone derivatives are good compounds which have been intensively used as biologically active compounds, e.g. anticancer, antibacterial, anticonvulsant, anti-inflammatory, antiulcer and analgesic [1,2,3]
The results of antibacterial tests demonstrated that 1 was most active against Staphylococcus aureus, Klebsiella pneumonia, Proteus bacilli and Shigella flexneri with inhibition zone 33, 29, 39 and 25 mm, respectively, while 26, 40, 25 and 25 mm, respectively, for 2
The antibacterial activities of the compounds were high and moderate when compared with the reference antibiotic chloramphenicol, 30 μg/mL
Summary
The quinazolinone derivatives are good compounds which have been intensively used as biologically active compounds, e.g. anticancer, antibacterial, anticonvulsant, anti-inflammatory, antiulcer and analgesic [1,2,3]. The quinazolines derivatives have been synthesized and characterized as active candidates [4]. Our aim is to investigate the antibacterial activity of 1 and 2. The structural and electronic properties were investigated by density functional theory (DFT) which has been used intensively and proved an efficient approach [6, 7]. The photophysical properties were studied by time dependent DFT (TDDFT). The light was shed on the chemical properties on the basis of computed descriptors, i.e. ionization potential (IP), electron affinity (EA), energy gap (Egap), electronegativity (χ), hardness (η), electrophilicity (ω), softness (S) and Abdullah G.
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