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An understanding of the fate of organic compounds originating from plants in soil is crucial for determining their persistence and concentrations in the environment. Aristolochic acids are believed to be the causal agents that induce Balkan endemic nephropathy by food contamination through soil adsorption of humic acids, major components of soil. Aristolochic acids are active chemicals in Aristolochia plant species found in endemic villages. In this article, molecular structure interactions between 18 structures of aristolochic acids with an inserted humic acid structure were studied. These structures were optimized in vacuo and by periodic box simulation with water solvate using the computational molecular mechanics MM+ method with HyperChem software. The QSPR models were used for correlation of the relationship between the hydrophobicity values of 18 AA structures coupled with a HA structure by MM+ and QSAR+ properties. Computational hydrophobicity values were considered dependent variables and were related to the structural features obtained by molecular and quantum mechanics calculations by multiple linear regression approaches. The obtained model was validated, and the results indicated differing hydrophobicity between the MM+ and QSAR+ properties.

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En este trabajo de investigación se realizó un estudio de relación estructura y actividad antioxidante empleando métodos computacionales basándose en propiedades estructurales y electrónicas, para lograr este objetivo se utilizó el programa computacional Hyperchem versión 8.0.1 empleando métodos cuánticos semiempiricos, a partir de las estructuras más estables obtenidas se calcularon longitudes de enlace, cargas atómicas, entalpias de disociación de enlace y orbitales moleculares de los cuatro flavonoides de Baccharis boliviensis aislados e identificados por el grupo de investigadores de Almanza, G. et.al en el año 2012. Al relacionar todos los datos obtenidos con la capacidad antioxidante se encontró que la actividad antioxidante entre los cuatro flavonoides el flavonoide 4 tiene mayor capacidad antioxidante debido al mayor número de grupos hidroxilo y a los valores bajos de energía de disociación de enlace EDE relativa respecto al flavonoide 1 que ocuparía el segundo lugar en términos de capacidad antioxidante, apoyan a estos resultados el hecho de considerar los valores de la segunda diferencia de energía de disociación de enlace EDE entre estos dos flavonoides se obtiene una diferencia de 1.106 H (Hartrees) para el flavonoide 4 y 1.4651H para el flavonoide 1. Los flavonoides 2 y 3 ocuparían las posiciones 3 y 4 en términos de capacidad antioxidante respectivamente. En conclusión la actividad antioxidante de los cuatro flavonoides estudiados presenta el siguiente orden de mayor a menor actividad antioxidante: flavonoide 4 > flavonoide 1 > flavonoide 2 > flavonoide 3.

In this research work was carried out a study of relationship structure and antioxidant activity using computational methods based on structural and electronic properties, to achieve this objective we used the computer program Hyperchem version 8.0.1 using semiempirical quantum methods, from structures More stable, bond lengths, atomic charges, bond dissociation enthalpies and molecular orbitals of the four Baccharis boliviensis flavonoids isolated and identified by the Almanza group, G Et.al in 2012, were calculated. By relating all the data obtained with the antioxidant capacity it was found that the antioxidant activity among the four flavonoids flavonoid 4 has higher antioxidant capacity due to the higher number of hydroxyl groups and the lower energy values of linkage dissociation EDE relative to flavonoid 1 that would occupy the second place in terms of antioxidant capacity, support to these results the fact of considering the values of the second energy difference of linkage dissociation EDE between these two flavonoids gives a difference of 1,106 H (Hartrees) for the flavonoid 4 and 1.4651H for flavonoid 1. The flavonoids 2 and 3 would occupy positions 3 and 4 in terms of antioxidant capacity respectively. In conclusion the antioxidant activity of the four flavonoids studied has the following order of highest to lowest antioxidant activity: Flavonoid 4> flavonoid 1> flavonoid 2> flavonoid 3.

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In this paper the structure-toxicity relationship studies were performed for a series of 60 phosphonates. The toxicity of the compounds was determined by two ways: by quantifying the measured toxicity values, Mlog(1/MRIC50) collected by literature, for rodents species; second by using EcoSAR software version 1.11, for calculating the toxicity for fish species, considered as dependent variables and they were related to structural features obtained by molecular and quantum mechanics calculations. The QSAR/QEcoSAR was validated by multiple linear regression (MLR), although the purpose of this work was not to validate the model proposed, but rather to test the influence of structural parameters of the proposed model QSAR/QEcoSAR. The obtained models showed that the toxicity of phosphonates was influenced by steric and molecular geometry which cause inhibition of cholinesterase activity.

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Infections caused by Candida species manifest in a number of diseases, including candidemia, vulvovaginal candidiasis, endocarditis, and peritonitis. Candida species have been reported to possess lipolytic activity due to the secretion of lipolytic enzymes such as esterases, lipases and phospholipases. Extra-cellular hydrolytic enzymes seem to play an important role in Candida overgrowth. Candidiasis is commonly treated with antimycotics such as clotrimazole and nystatin. The antimycotics bind to a major component of the fungal cell membrane (ergosterol), forming pores that lead to death of the fungus. However, the secondary effects caused during such treatment have aroused a need to develop a treatment based on lipase inhibition. Nonetheless, no such lipase inhibitors for candidiasis treatment are currently available. Thus, we have performed a docking study with the natural inhibitor, orlistat or tetrahydrolipstatin. Our results have shown ten possible binding inhibitors to Candida rugosa lipase (CRL), out of which one possibility was selected, based on the weakest interatomic distance of 2.7 Å. Therefore, we propose the selection and design of a potential inhibitor candidate, orlistat for the treatment of candidiasis infections. However, this study has to be supported with in vitro and in vivo experiments to demonstrate the effectiveness of orlistat in lipase inhibition.

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Ribulose-1, 5- Bisphosphate carboxylase/ oxygenase (RubisCO) catalyzes the first step in net photosynthetic assimilation and photorespiratory carbon oxidation. The activity of this enzyme is modulated in response to changes in light intensity as suggested in a number of early reports. Several studies found that the natural inhibitor 2CA1P is involved in the inhibition of the enzyme under reduced light intensity in rice (Oryza sativa). Due to the lack of studies and information on the interaction between this inhibitor and the active site of the enzyme, we attempted to predict the interaction between the amino acids in the active site and the inhibitor using both Hyperchem7.5 and GOLD software. After the docking; three possibilities having the highest fitness score were found (65.71, 64.72, 62.04), in these possibilities the inhibitor was bound to the enzyme, the phosphate and carboxylate groups in the same positions with a clear difference in the position of OH. In order to confirm the accuracy of the genetic algorithm, the artificial inhibitor 2CABP was docked back in the active site of the enzyme using the same parameters used in the case of the 2CA1P and the algorithm's predictions were compared with the experimentally observed binding mode. The results showed that the difference in the active sites before and after the docking was in the range of 0.93 A which indicated that the results were very accurate. Depending on this result it was concluded that the results obtained in the case of the 2CA1P were close to the experimental results.