Banca de DEFESA: JOÃO CARLOS SILVA CONCEIÇÃO

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
DISCENTE : JOÃO CARLOS SILVA CONCEIÇÃO
DATA : 26/04/2019
HORA: 09:00
LOCAL: Sala de Seminários
TÍTULO:

In vitro and in silico studies of biotransformations of phenolic substances

PALAVRAS-CHAVES:

Biotransformation. Filamentous fungi. Phenolic substances. Molecular docking.

PÁGINAS: 142
GRANDE ÁREA: Ciências Exatas e da Terra
ÁREA: Química
SUBÁREA: Química Orgânica
ESPECIALIDADE: Química dos Produtos Naturais
RESUMO:

Biotransformation processes have an important role in chemical derivatization since the enzymes and their cofactors are generated in situ, acting as efficient catalysts that modify different substrates. In general, biotransformation reactions present high selectivity and are according to the Green Chemistry principles. Phenolic substances have numerous bioactivities and are useful for several industries to producing derivatives with high added value. Within this context, in the present study, the biotransformations of three phenolic substances were analyzed using two strains of filamentous fungi: Trametes versicolor ATCC 200801 and Aspergillus brasiliensis ATCC 16404. The fungus T. versicolor is a traditional source for the enzyme laccase (an oxidoreductase). The chemical profiles of the biotransformations were evaluated by using Thin Layer Chromatography (TLC), High-Efficiency Liquid Chromatography coupled to Diode Array Detector (HPLC-DAD) and Gas Chromatography coupled to Mass Spectrometry (GC-MS), and the most promising processes for the biotransformation of the evaluated substrates were selected. The obtained derivatives were isolated by chromatographic column using silica gel as the stationary phase and ethyl acetate, hexane and methanol as the mobile phase. Spectroscopic and spectrometric techniques were used to determine the chemical structures of the derivatives. It was possible to observe that T. versicolor biotransformed only methyl p-coumarate, resulting in the formation of three derivatives: cumaric acid, yield of 12.18 %; methyl caffeate, yield of 3.56%; and (E)-methyl-3- (4-methoxyphenyl) acrylate (identified in mixture). Biotransformations by A. brasiliensis resulted in the conversion of methyl p-coumarate into three derivatives (detected by GC-MS): acetophenone, 1-(4-hydroxyphenyl) propane-1,3-diol and 4-(3-hydroxypropyl) benzene-1,2-diol; methyl ferulate was biotransformed into (4)-methyl-3-(4-hydroxy-3-methoxyphenyl)-3-methoxyacrylate (10.31 % yield). Additionally, the biotransformation of the three phenolic substrates by T. versicolor was studied by in silico assays. It was considered that the enzyme present in the reaction medium was laccase and the molecular docking was carried out. The AutoDock v.4.2 and Pymol softwares provided a prediction of the orientation and preferential conformation that the phenolic substrates took on the active site of laccase. The results indicated that the three substrates interacted spontaneously with the biological receptor, but with different free energy values (ΔG): ΔG p-methyl coumarate = -6.89 Kcal.mol^-1, ΔG methyl ferulate = -7, 37 Kcal.mol^-1 and ΔG methyl caffeate = -7.55 Kcal.mol^-1. The ligand-protein complex consisting of methyl p-coumarate-laccase was the least stable one, explaining the occurrence of biotransformation of this substrate by T. versicolor. Thus, it was possible to demonstrate that methyl p-coumarate interacted more efficiently with the laccase site, allowing the occurrence of hydrolysis, hydroxylation and methoxylation reactions.

MEMBROS DA BANCA:
Presidente - 1148522 - ELIANE DE OLIVEIRA SILVA
Interno - 1068075 - JORGE MAURICIO DAVID
Externo ao Programa - 1889116 - SAMUEL SILVA DA ROCHA PITA