Manuel Villanueva-García

Synthesis and in Vitro Antioxidant Activity Evaluation of 3-Carboxycoumarin Derivatives and QSAR Study of Their DPPH• Radical Scavenging Activity

The in vitro antioxidant activities of eight 3-carboxycoumarin derivatives were assayed by the quantitative 1,1-diphenyl-2-picrylhydrazil (DPPH•) radical scavenging activity method. 3-Acetyl-6-hydroxy-2H-1-benzopyran-2-one (C1) and ethyl 6-hydroxy-2-oxo-2H-1-benzopyran-3-carboxylate (C2) presented the best radical-scavenging activity. A quantitative structure-activity relationship (QSAR) study was performed and correlated with the experimental DPPH• scavenging data. We used structural, geometrical, topological and quantum-chemical descriptors selected with Genetic Algorithms in order to determine which of these parameters are responsible of the observed DPPH• radical scavenging activity. We constructed a back propagation neural network with the hydrophilic factor (Hy) descriptor to generate an adequate architecture of neurons for the system description. The mathematical model showed a multiple determination coefficient of 0.9196 and a root mean squared error of 0.0851. Our results shows that the presence of hydroxyl groups on the ring structure of 3-carboxy-coumarins are correlated with the observed DPPH• radical scavenging activity effects.

Quadrupolar moment calculations and mesomorphic character of model dimeric liquid crystals

Abstract Model dimeric compounds CH3(CH2)nCOOROOC(CH2)pCOOROOC(CH2)nCH3, where (R=C6H4C(CH3)HCC6H4), of semiflexible liquid crystal polymers (LCP) have been studied by molecular modeling techniques. First, a conformational analysis of the molecules was made in order to find the lowest energy conformation structure. In a second stage, geometry optimization calculations of these conformers were performed at the quantum mechanics semiempirical PM3 level. Some molecular parameters (electric dipolar and quadrupolar moments) were obtained at the improved ab initio Hartree–Fock HF/6-31G(d)//PM3 level and are related with the mesomorphic character of these systems. It is found that the trace of the quadrupole moment tensor correlates with the spacer ((CH2)p-linkage) length, and this can be an indication of the trend that this magnitude exhibits in aromatic liquid crystal systems.

QSAR study of the DPPH· radical scavenging activity of coumarin derivatives and xanthine oxidase inhibition by molecular docking

AbstractA Quantitative Structure-Activity Relationship (QSAR) of coumarins by genetic algorithms employing physicochemical, topological, lipophilic and electronic descriptors was performed. We have used experimental antioxidant activities of specific coumarin derivatives against the DPPH· radical molecule. Molecular descriptors such as Randic Path/Walk, hydrophilic factor and chemical hardness were selected to propose a mathematical model. We obtained a linear correlation with R2 = 96.65 and QLOO2 = 93.14 values. The evaluation of the predictive ability of the model was performed by applying the QASYM2,

Derivation by Electronic Structure Calculations of the Aspect Ratios (Length/Diameter) for Homologous Series of Calamitic Liquid Crystals

\hat r^2

Quantitative structure-activity relationship of molecules constituent of different essential oils with antimycobacterial activity against Mycobacterium tuberculosis and Mycobacterium bovis

and Δrm2 methods. Fukui functions were calculated here for coumarin derivatives in order to delve into the mechanics by which they work as primary antioxidants. We also investigated xanthine oxidase inhibition with these coumarins by molecular docking. Our results show that hydrophobic, electrostatic and hydrogen bond interactions are crucial in the inhibition of xanthine oxidase by coumarins.

Quantitative structure-property relationships to estimate nematic transition temperatures in thermotropic liquid crystals

ABSTRACT 4′-Methyl-biphenyl-4-carbonitrile and the 4′-Methoxy-biphenyl-4-carbonitrile homologous series are known to exhibit calamitic (nematic and/or smectic) liquid crystal phases. In this work, aspect ratios x (length/diameter) for these molecules are computed from electronic structure calculations using ab initio HF/3-21G//PM3 level of theory/numerical precision. Aspect ratios were calculated from ovality Ov, defined as Ov=(A/4π)/(3V/4π)2/3, where V is the molecular volume and A the surface area. Derivations of thermotropic liquid crystal aspect ratios as a function of Ov, by this model are in agreement with observed values and permit an adequate description of the liquid crystal molecular geometry.