Estudo Fitoquímico de Brosimum potabile Ducke e Brosimum acutifolium Huber, visando investigar por métodos teóricos, o mecanismo de biotransformação de β-sitosterol em Estigmaterol

Abstract

The phytochemical study of Bosimum acutifolium, Huber and Brosimum potabile, Ducke is being reported im this work. The compounds β-sitosterol and stigmasterol were identified of isolated mixtures containing both them in the two studied species and additionally from B. potabile was isolated the (-)-centrolobin as well. The later is a phytoconstituent of the diaryl-heptanoids chemical class which was characterized by spectroscopic data. The importance of thse results is due to the biological significance of the diatyl-heptanoids, and mainly because this class of compounds has not been reported in species of Brosimum genus until now. GC/MS and 1H NMR analyses of the steroids mixture have shown variations concerned to the relative amount of their constituents in different areas of one of the studied species as well as in both species. Considering the possibility of biotransformation of β-sitosterol to stigmasterol, the electronic and steric properties of β-sitosterol were calculated. Such properties were calculated as well for the Osubstitute group’s effect considering the methylated, acetylated, glycosilated and phosphorylated β-sitosterol. The calculations in this theoretical study were done evaluating electronic density, contribution of atomic to molecular orbital, frontier molecular orbital energy, interatomic distances and thermodynamic studies. From the obtained data, was possible to infer over the biotransformation mechanism of β-sitosterol to stigmasterol. On generally, it was noted a significant effect over the thermodynamic data of the Osubstitued products of β-sitosterol, as a consequence of the conformational steroidal branching. Moreover, in spite of the distance form the carbon O-C-3 and the β- sitosterol steroidal branching, was noted as well the effect of the strucuture of the Osubstitute group over the electronic and steric properties in C-22 and C-23 for its biotransformation to stigmasterol.