Banca de DEFESA: MOACIR FERNANDES DE QUEIROZ NETO

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
DISCENTE : MOACIR FERNANDES DE QUEIROZ NETO
DATA : 29/07/2019
HORA: 08:30
LOCAL: Sala Carl Peter von Dietrich - Departamento de Bioquímica
TÍTULO:

Polysaccharides' (chitosan and dextran) antioxidant activity enhancement through its combination with gallic acid.

PALAVRAS-CHAVES:

Calcium oxalate; oxidative stress; glucan; Leuconostoc ssp.; factorial design; free radicals

PÁGINAS: 113
GRANDE ÁREA: Ciências Biológicas
ÁREA: Bioquímica
RESUMO:

Oxidative stress occurs in cells when there is an imbalance between the amount of antioxidants and oxidants in favor of the latter, which therefore can cause more than 100 diseases. In order to combat this situation, exogenous antioxidants can be used. For this reason, there is a search for different sources of antioxidant molecules, including semi-synthetic or synthetic compounds. Polysaccharides are natural molecules whose antioxidant capacity varies according to the polysaccharide type and can be modified with polysaccharide conjugation with different groups such as gallic acid (GA). Chitosan and dextran are two of the most abundant polysaccharide families in the nature and have several applications. However, they have a low antioxidant potential, which restricts their use. In this work, using a green conjugation method, it was possible to conjugate GA to chitosan and dextran and the conjugation was confirmed by the phenolic contend dosage, infrared and nuclear magnetic resonance spectrometries. It was possible to incorporate 10.2 ± 1.5 mg GA/chitosan g, which resulted in a 2-fold increase in total antioxidant capacity (TAC), 5-fold increase in reducting power, and the occurrence of a ferric chelation activity (about 60%) not observed with native chitosan. In addition, the conjugate was also able to prevent the exacerbated formation of calcium oxalate crystals in vitro, which was observed with the native chitosan. As regards to dextran, it is worth noting that this is the first report of GA conjugation to this polysaccharide, which in this case was 36.8 ± 1.4 mg GA/dextran g. Due to its novelty, the process of conjugation of dextran with GA was subjected to a factorial design in order to understand how the variables (amount of peroxide and amount of GA) influenced the synthesis of conjugated dextran; in its antioxidant activities; and to obtain an ideal conjugation condition of GA to dextran. It was verified that the amount of GA in the conjugation process is inversely proportional to the antioxidant activities, and that the ideal condition for production of a molecule with maximum antioxidant potential is that produced with 1.2M of hydrogen peroxide and a 1:1 ration of GA to dextran. The ideal molecule had CAT of 60 mg AA/dextran g, copper chelation of about 50%, and a reducing power close to 90%. In short, the GA green conjugation method was efficient for both chitosan and dextran and in both cases it was possible to increase the antioxidant potential of these polysaccharides, indicating a feasible use of these derivatives as substituents of their native molecules in various applications.

MEMBROS DA BANCA:
Presidente - 2195251 - HUGO ALEXANDRE DE OLIVEIRA ROCHA
Interno - 2962496 - RAFAEL BARROS GOMES DA CAMARA
Externo à Instituição - DIEGO DE ARAUJO SABRY - IFRN
Externo à Instituição - RANIERE FAGUNDES DE MELO SILVEIRA
Externa à Instituição - VALQUIRIA PEREIRA DE MEDEIROS - UFJF