Antioxidant Activity of Plant Extracts from Brazilian Flora: Study of Electron Paramagnetic Resonance (EPR) and Density Functional Theory (DFT). / Atividade antioxidante de extratos vegetais da flora brasileira: estudo com ressonância paramagnética eletrônica (RPE) e teoria do funcional da densidade (TFD)

AUTOR(ES)
DATA DE PUBLICAÇÃO

2006

RESUMO

There is, in Brazil, a great diversity of vegetable species, and a popular knowledge of several medicinal properties of the some of them. In studies carried out with plants? extracts, there is special interest in antioxidant activities. This work, focused in antioxidant activity, is divided in two parts: the first uses EPR technique to study the antioxidant activities neutralizing free radicals, while the second one uses DFT, in computational simulation, to understand the results obtained from the first part. Ten vegetable extracts were analyzed: Swartzia langsdorffii, Machaerium villosum, Pterogyne nitens, Maytenus ilicifolia (bark root extracts), Pera glabrata, Aegiphyla sellowiana, Copaifera langsdorffii, Chrysophyllum inornatum, Iryanthera juruensis (leaves and seeds), Didymopanax vinosum. The study with EPR uses two different methods: the first method measures the antioxidant activity by monitoring the amount of free radicals, DPPH and TEMPOL, that are in contact with the plant extract, the second method uses spin trap DMPO with Fenton reaction (Fe2+ + H2O2 =>Fe3+ + HO- + HO) for the study of the plant extract antioxidant activity against the hydroxyl radical (OH?). The computational simulation of TEMPOL, DPPH and DMPO is carried out using a method of first principles within the Density Functional Theory and pseudopotentials. The code is SIESTA. The conclusions indicate that the Iryanthera juruensis extract, as of leaves as of seeds, exhibits accentuated antioxidants activities, in all of the used methods. The computational simulation indicated that the TEMPOL is less reactive than the DPPH, because the lower energy in its reduction reaction. As some of these species are already used popularly by medicinal properties, future studies for correct identification of the antioxidant compounds and its possible use, as in the food industry as in the pharmaceutical industry, should be realized.

ASSUNTO(S)

antioxidant tempol fenton reaction ressonância paramagnética eletrônica (rpe) tempol antioxidante reação de fenton teoria do funcional da densidade (tfd). density functional theory (dft). dpph free-radicals dmpo dmpo vegetal extract electron paramagnetic resonance (epr) dpph radicais livres extrato vegetal

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