RESUMO
Antioxidants agents play an essential role in the food industry for improving the oxidative stability of food products. In the last years, the search for new natural antioxidants has increased due to the potential high toxicity of chemical additives. Therefore, the synthesis and evaluation of the antioxidant activity in peptides is a field of current research. In this study, we performed a Quantitative Structure Activity Relationship analysis (QSAR) of cysteine-containing 19 dipeptides and 19 tripeptides. The main objective is to bring information on the relationship between the structure of peptides and their antioxidant activity. For this purpose, 1D and 2D molecular descriptors were calculated using the PaDEL software, which provides information about the structure, shape, size, charge, polarity, solubility and other aspects of the compounds. Different QSAR model for di- and tripeptides were developed. The statistic parameters for di-peptides model (R2train = 0.947 and R2test = 0.804) and for tripeptide models (R2train = 0.923 and R2test = 0.847) indicate that the generated models have high predictive capacity. Then, the influence of the cysteine position was analyzed predicting the antioxidant activity for new di- and tripeptides, and comparing them with glutathione. In dipeptides, excepting SC, TC and VC, the activity increases when cysteine is at the N-terminal position. For tripeptides, we observed a notable increase in activity when cysteine is placed in the N-terminal position.
Assuntos
Antioxidantes , Cisteína , Dipeptídeos , Oligopeptídeos , Relação Quantitativa Estrutura-Atividade , Cisteína/química , Antioxidantes/química , Antioxidantes/farmacologia , Dipeptídeos/química , Dipeptídeos/farmacologia , Oligopeptídeos/química , Oligopeptídeos/farmacologia , Modelos Moleculares , SoftwareRESUMO
Although many sulfur containing garlic compounds present antioxidant activity, little is known about molecular mechanisms through which these compounds react with reactive oxygen species. In this work, the reactivity and the hydrogen peroxide scavenger reaction mechanisms (including thermodynamics and kinetics aspects) of allyl methyl disulfide in aqueous phase are studied employing density functional theory computational methods. Three reactive sites susceptible for electrophilic attack are found over sulfur atoms and the double bond allyl moiety. For each detected site, one redox reaction is proposed and analyzed. All reactions are thermodynamically feasible, whereas attack over the methyl bound sulfur atom is kinetically favored.
Assuntos
Antioxidantes/química , Dissulfetos/química , Peróxido de Hidrogênio/química , Alho , Cinética , Modelos Químicos , Eletricidade Estática , TermodinâmicaRESUMO
Quantum chemical methods have been used to study the conformational and electronic properties of sulfanilamide and derivatives with antibacterial activity. Calculations at B3LYP/6-311++G(3df,2p) level of theory predict the existence of four conformers for sulfanilamide depending on the orientation of p-amino and amide groups. Focusing on the sulfonamide moiety, amide NH(2) and SO(2) groups could exist either in an eclipsed or staggered arrangement. Gas-phase results predict the eclipsed conformer to be most stable but opposite to what has been rationalized previously, no stabilizing hydrogen bonds between those groups has been found through NBO analysis. When solvent effect is taken into account through the IEF-PCM method, staggered conformer is preferred; in fact, eclipsed conformation changed when explicit solvent molecules were included. Conformational analysis of all derivatives has shown two global minima which are specular images. Five out of the seven derivatives studied adopted a particular minimum energy conformation with very similar geometries.