Banca de DEFESA: DANYELLE CANDIDO SANTOS

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : DANYELLE CANDIDO SANTOS
DATE: 24/02/2022
TIME: 09:00
LOCAL: Webconferência
TITLE:

Antioxidant Evaluation and Bioelectrochemical Investigation of Nitrone’ Derivatives

KEY WORDS:

Nitrones. Nitroaromatics. Organic electrochemistry. Cyclic voltammetry. Redox mechanism. Antioxidant Capacity

PAGES: 106
BIG AREA: Ciências Exatas e da Terra
AREA: Química
SUBÁREA: Química Orgânica
SUMMARY:

Nitrones are known for their ability to capture radicals and consequently reduce oxidative stress, making them
promising synthetic antioxidants with high therapeutic potential. They are being studied for the treatment of various
pathologies, such as cancer, stroke, Parkinson's and Alzheimer's diseases, including neglected tropical diseases.
Since the molecular mechanism of biological action of this group of compounds is not yet fully elucidated, the present
work investigated the electrochemical, spectroelectrochemical and spectrophotometric behavior of synthetic nitrones,
derivatives and precursors. In addition, their antioxidant capacity was evaluated by spectroscopic methods of FRAP
(Ferric reducing/antioxidant power) and antioxidant capacity against the DPPH• radical (2-2-diphenyl-1-picrylhydralazine). Cyclic (CVs) and differential pulse (DPVs) voltammograms on a glassy carbon electrode (GCE) were
recorded in an aprotic medium (acetonitrile + 0.1 M TBAPF6) in order to mimic the lipophilic biological environments
and obtain data on the mechanism of reduction, oxidation, analysis of electrogenerated intermediates, in the
perspective of contributing to the elucidation of their molecular mechanisms of biological action. The pnitrobenzaldehyde and 5-nitro-2-furaldehyde standards were studied electrochemically under the same conditions. All
compounds studied showed electrochemical activity in the cathodic bands of the voltammograms. The LQB-109 and
LQB-123 nitrones showed similar behavior, with irreversible reduction waves and a potential more negative than -2.0
V, relative to the nitrone reduction. As for the compounds LQB-569, LQB-303, LQB-484, LQB-304 and LQB-534 that
have double redox function, that is, nitrone group and nitro group, peaks characteristic of both were observed. When compared to the standards (compounds that have only the nitrone group or only the nitro group), it is noted that the
nitraromatic group is reduced first in a reversible monoelectronic transfer. The spectroelectrochemical investigation for
the nitronitrone LQB-303 revealed a decrease in the absorbance of some absorption bands and the emergence of new
ones, during the application of cathodic potentials, which suggest the reduction of nitronitrone and formation of its
reduction products. In the investigation of the antioxidant capacity, the values of the percentage of radical scavenging
activity (%RSA) for the DPPH• radical ranged from 10.14 - 37.25% inhibition, while the FRAP values ranged from
126.86 - 196, 84 mg trolox equivalent (TE)/mol of compound. In the analysis of the optical properties of these
compounds using UV-Vis spectroscopy, all compounds showed absorptions in the UV-Vis region between 190 - 900
nm. The interaction between DDQ and LQB-109 revealed the emergence of new bands in the region 400 – 600 nm,
suggesting the formation of the charge transfer complex. Electrochemical methods proved to be adequate in the redox
study of nitrones, derivatives and precursors and were correlated with leishmanicidal activities, mainly for the
nitronitrones LQB-303 and LQB-484, which were significantly leishmanicidal, with low toxicity

BANKING MEMBERS:
Externo à Instituição - AYRES GUIMARÃES DIAS - UERJ
Interna - 1006306 - JADRIANE DE ALMEIDA XAVIER
Interno - 1613338 - JOSUE CARINHANHA CALDAS SANTOS
Presidente - 2120103 - MARILIA OLIVEIRA FONSECA GOULART
Externa ao Programa - 1320545 - THAISSA LUCIO SILVA
Interno - 1609640 - VINICIUS DEL COLLE