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International audience; An efficient process was described to prepare a novel 6‑bromo‑2‑chloro‑3-butylquinazolin-4(3H)-one. The targeted compound was synthesized from available chemicals and assessed for anti-bacterial activity. This new compound structure crystallises in the triclinic system with P-1 space group. Its unit cell parameters are (a = 4.91550(10) Å, b = 11.4764(2) Å, c = 12.1670(3) Å), volume (638.11(4) Å3), α= 110.079(8)°, β= 93.8130(10)°, γ = 95.4580(10)° and Z = 2. The crystal packing was stabilized by C = O…H hydrogen bonds and CH3CH2CH2CH2CHH….C π-stacking interaction and hydrogen π-π stacking interactions. Hirshfeld surfaces and their associated two-dimensional fingerprint plots were used to analyze the intermolecular interactions in the crystal structure. In addition, electrostatic surface potential (ESP) was generated using the density functional theory.

International audience; An efficient route was reported for synthesis of a novel 3-(4-fluorophenyl)-6-methyl-2-(propylthio)quinazolin-4(3H)-one. The synthesized compound was prepared by a sulphur arylation reaction and was tested against some bacterial strains. Raman analysis was conducted on the synthesized derivative, which had the following properties: empirical formula (C18H17Cl N2 O), system (monoclinic), space group (P21/c), unit parameters cell (a = 12.7137(7) Å, b = 7.5018(4) Å, c = 17.1209(9) Å and β =11.0042(15)°), volume (V = 1524.42 Å3), Z = 4, temperature (150 (2) K). The single crystal structure was resolved and refined to (R = 0.0374, wR = 0.1040). The non-hydrogen atoms were refined anisotropically and the hydrogen atoms were placed theoretically. The Hirshfeld surface and fingerprint plots were obtained. The electrostatic potential surface (ESP) was also derived using the density functional theory method.

International audience; Quantum calculations (mainly DFT) and molecular dynamics are increasingly effective tools to evaluate the physico-chemical properties of natural and bio-inspired antioxidants. Thermodynamic parameters (mainly bond dissociation enthalpies (BDE) of the O-H phenolic bond) allowed an accurate prediction of the Free Radical Scavenging Capacity of natural and hemi-synthetic compounds. Based on the Transition State and the Marcus Theories (for atomand electron-transfers, respectively), kinetics was also evaluated providing a better prediction of the antioxidant behaviour in solution or in the organism. Also pro-oxidant effects have been studied including the oxidatively-induced dimerization capacity. In this case, thermodynamic and kinetic calculations explain regio- and stereo-selectivity. MD simulations have been performed to provide an accurate picture of the interaction between natural antioxidants (polyphenols and other π-conjugated derivatives) and lipid bilayer membranes. Molecular dynamics allows evaluation of the ability of these molecules to approach and penetrate the membrane, and to predict their "exact" location and orientation.

International audience; Phenolic Schiff bases are known for their diverse biological activities and ability to scavenge free radicals. To elucidate (1) the structure-antioxidant activity relationship of a series of thirty synthetic derivatives of 2-methoxybezohydrazide phenolic Schiff bases and (2) to determine the major mechanism involved in free radical scavenging, we used density functional theory calculations (B3P86/6-31+(d,p)) within polarizable continuum model. The results showed the importance of the bond dissociation enthalpies (BDEs) related to the first and second (BDEd) hydrogen atom transfer (intrinsic parameters) for rationalizing the antioxidant activity. In addition to the number of OH groups, the presence of a bromine substituent plays an interesting role in modulating the antioxidant activity. Theoretical thermodynamic and kinetic studies demonstrated that the free radical scavenging by these Schiff bases mainly proceeds through proton-coupled electron transfer rather than sequential proton loss electron transfer, the latter mechanism being only feasible at relatively high pH.

Natural polyphenols are known to exhibit a lot of different biological properties, including antioxidant activity. For some polyphenols these activities are attributed to the presence of a guaiacol moiety. In the present paper we focus on the role of this moiety. For this purpose nine different compounds were enzymatically synthesized from guaiacol. To elucidate the structure-activity relationship of these polyphenols, DFT-(PCM)B3P86/6-311+G(2d,3pd)//(PCM)B3P86/6-31+G(d,p) calculations supported the experimental DPPH free radical scavenging activities. The antioxidant activities were correlated to (i) O-H BDEs (bond dissociation enthalpies), (ii) BDE(D) (BDE of a second H atom abstraction from the phenoxyradicals), (iii) spin density, (iv) HOMO (highest occupied molecular orbital) distribution, (v) IPs (ionization potentials), (vi) DeltaG and DeltaG(#) free energies of HAT (H atom transfer), and (vii) HAT rate constants. BDE(D) appeared to be the most important descriptor to understand the free radical scavenging ability of these compounds.