Antioxidant properties of plant extracts: an EPR and DFT comparative study of the reaction with DPPH, TEMPOL and spin trap DMPO

Abstract

Este trabalho apresenta um estudo comparativo da atividade antioxidante dos extratos de nove espécies de plantas pertencentes à flora brasileira -Swartzia langsdorffii, Machaerium villosum, Pterogyne nitens, Pera glabrata, Aegiphyla sellowiana, Copaifera langsdorffii, Chrysophyllum inornatum, Iryanthera juruensis, Didymopanax venosum -neutralizando os radicais livres DPPH (2,2-difenil-1-picrilhidrazil) e TEMPOL (4-hidróxi-2,2,6,6-tetrametil-1-piperidiniloxi-1-oxil) utilizando ressonância paramagnética eletrônica (RPE), e agindo sobre os radicais hidroxila (OH·) gerados por uma reação Fenton, através da técnica de spin-trapping. Os melhores resultados foram obtidos para os extratos de Iryanthera juruensis e Chrysophyllum inornatum. Os resultados dos testes foram acompanhados por cálculos computacionais dos compostos, utilizando a teoria do funcional da densidade (TFD), com aproximação local da densidade (ALD), e o código SIESTA. Os resultados indicaram que a energia liberada na reação de redução TEMPOL é inferior a DPPH. Como o DPPH é um composto de menor custo e mais disponível tem um uso mais amplo que o TEMPOL, entretanto este último deve ser considerado quando se quer estudar processos que envolvam menores energias.This work presents a comparative study of the antioxidant activity of extracts from nine plant species belonging to the Brazilian flora -Swartzia langsdorffii, Machaerium villosum, Pterogyne nitens, Pera glabrata, Aegiphyla sellowiana, Copaifera langsdorffii, Chrysophyllum inornatum, Iryanthera juruensis, Didymopanax venosum -acting on the free-radicals DPPH (2,2-diphenyl-1-picrylhydrazyl) and TEMPOL (4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy-1-oxyl) by electron paramagnetic resonance (EPR), and acting on the hydroxyl radical (OH·) by the spintrapping technique generated by a Fenton reaction. Results showed that the extracts of Iryanthera juruensis and Chrysophyllum inornatum display the strongest antioxidant activities. The results of scavenging tests were clarified by computational calculations -density functional theory (DFT), local density approximation (LDA) with SIESTA code -indicating that the energy released in the reduction reaction of TEMPOL is less than DPPH. Due to its availability and cost DPPH is more often used in these tests than TEMPOL, however TEMPOL should be considered when studying processes dealing with smaller energies.

Radical Scavenging Capacity of Seeds and Leaves Ethanol Extracts ofCynara Scolymus L.—A Comparative Study

“…The fact that the DPPH EPR spectrum has a relatively simple signal due only to the free radical is an advantage in relation to the optical spectroscopy. In the latter, besides the appearance of absorptions due to the presence of other compounds in the extract, there is also an increment at 320 nm, corresponding to the increase in DPPH-H concentration due to DPPH reduction to the respective hydrazine (27,20). Results obtained for the DPPH radical scavenging capacity of the studied extracts by the EPR spectroscopy technique are presented on Fig.…”

Interference of Seasonal Variation on the Antimicrobial and Cytotoxic Activities of the Essential Oils from the Leaves of Iryanthera polyneura in the Amazon Rain Forest

“…Regarding the individual 530EO, the oils 530EO3 and 530EO7 showed the lower IC 50 values and demonstrated significantly greater cytotoxic activity against breast and prostate cancer cells, respectively. Previous studies using extracts from I. juruensis also showed cytotoxic activity against cancer cells, as K562, a bone marrow cell line, although there have been no reports investigating the cytotoxic activity of the essential oils from the species. Nonetheless, the oils obtained from nutmeg, Myristica fragrans , were able to expressively inhibit MCF‐7 (IC 50 66.45 μg/mL) and HCT‐116, a human colorectal carcinoma cell line (IC 50 78.61 μg/mL) …”

Electron Paramagnetic Resonance Spectrometry-based Assessment of Free Radicals Scavenging Potential of N-acetyl Tryptophan Glucoside

“…However, EPR spectrometric method possesses advantages over the spectrophotometric assays, because EPR spectrometry involved direct measurement of free radicals in a biological or chemical system. While, optical spectroscopic assessment is an indirect method of free radicals analysis 8,26 . Therefore, observations reported in the present study for DPPH, ascorbate, nitric oxide and superoxide radicals scavenging activity of NATG using EPR spectrometry was considered more explicit than those by spectrophotometry.…”