Banca de QUALIFICAÇÃO: MOACIR FERNANDES DE QUEIROZ NETO

Uma banca de QUALIFICAÇÃO de DOUTORADO foi cadastrada pelo programa.
DISCENTE : MOACIR FERNANDES DE QUEIROZ NETO
DATA : 15/07/2019
HORA: 16:00
LOCAL: Sala Carl Peter von Dietrich - Departamento de Bioquímica
TÍTULO:

Oxidative stress is caused by the balance breakdown between oxidants and antioxidants in the body. When this occurs, there is excessive damage caused by reactive species. Over 100 diseases have some kind of link to oxidative stress. One way to counter oxidative stress is the use of exogenous antioxidants. Several molecules can be used as exogenous antioxidants, such as polysaccharides. Polysaccharide are very abundant molecules in nature and have diverse biological activities, including antioxidant activity. However, due to its abundance and variability not all polysaccharides possess antioxidant activities to the same extent. And sometimes those most abundant have low or no antioxidant activity reported. Chitosan and dextran are some of these polysaccharides that are easy to obtain and abundant, as well as being widely used in the pharmaceutical, food, cosmetic and other industries. However, the antioxidant activity of these molecules is generally low. One way to increase the antioxidant capacity of these polysaccharides would be to conjugate them with gallic acid. Gallic acid (GA) is a secondary metabolite of plants from the family of phenolic compounds, these molecules, due to their structure and functional groups, have high antioxidant capacity. In this work, it was possible to conjugate GA to chitosan and dextran by a green conjugation method that uses free radicals, obtaining conjugates with 10.2 ± 1.5 mg and 36.8 ± 1.4 mg of GA/g of compound respectively. The conjugation was confirmed by infrared and nuclear magnetic resonance analyzes. For conjugated chitosan there was a 2-fold increase in total antioxidant capacity (CAT), 5 times in the reducing power, and an iron chelation acativity (about 60%) appeared, an activity not observed in the native chitosan, in addition the conjugation also was able to prevent the excessive formation of calcium oxalate crystals in vitro. As for dextran, the activity of the conjugate was improved 13 times the CAT test, in addition, superoxide radical scavenging (60%) and reducing power (90%) activites were detected, it’s worth noting that these activities were not detected with native dextran. The results show that the GA green conjugation method was efficient for both chitosan and dextran and in both cases it was possible to increase the antioxidant capacity of these polysaccharides, indicating a potential use of these derivatives as substitutives of their native molecules in the various applications of these polysaccharides

PALAVRAS-CHAVES:

kidney stones; urolithiasis, gallic acid-grafting; Glucan, Oxidative Stress; Leuconostoc ssp;

PÁGINAS: 72
GRANDE ÁREA: Ciências Biológicas
ÁREA: Bioquímica
RESUMO:

Oxidative stress is caused by the balance breakdown between oxidants and antioxidants in the body. When this occurs, there is excessive damage caused by reactive species. Over 100 diseases have some kind of link to oxidative stress. One way to counter oxidative stress is the use of exogenous antioxidants. Several molecules can be used as exogenous antioxidants, such as polysaccharides. Polysaccharide are very abundant molecules in nature and have diverse biological activities, including antioxidant activity. However, due to its abundance and variability not all polysaccharides possess antioxidant activities to the same extent. And sometimes those most abundant have low or no antioxidant activity reported. Chitosan and dextran are some of these polysaccharides that are easy to obtain and abundant, as well as being widely used in the pharmaceutical, food, cosmetic and other industries. However, the antioxidant activity of these molecules is generally low. One way to increase the antioxidant capacity of these polysaccharides would be to conjugate them with gallic acid. Gallic acid (GA) is a secondary metabolite of plants from the family of phenolic compounds, these molecules, due to their structure and functional groups, have high antioxidant capacity. In this work, it was possible to conjugate GA to chitosan and dextran by a green conjugation method that uses free radicals, obtaining conjugates with 10.2 ± 1.5 mg and 36.8 ± 1.4 mg of GA/g of compound respectively. The conjugation was confirmed by infrared and nuclear magnetic resonance analyzes. For conjugated chitosan there was a 2-fold increase in total antioxidant capacity (CAT), 5 times in the reducing power, and an iron chelation acativity (about 60%) appeared, an activity not observed in the native chitosan, in addition the conjugation also was able to prevent the excessive formation of calcium oxalate crystals in vitro. As for dextran, the activity of the conjugate was improved 13 times the CAT test, in addition, superoxide radical scavenging (60%) and reducing power (90%) activites were detected, it’s worth noting that these activities were not detected with native dextran. The results show that the GA green conjugation method was efficient for both chitosan and dextran and in both cases it was possible to increase the antioxidant capacity of these polysaccharides, indicating a potential use of these derivatives as substitutives of their native molecules in the various applications of these polysaccharides

MEMBROS DA BANCA:
Presidente - 2832746 - MONIQUE GABRIELA DAS CHAGAS FAUSTINO ALVES
Externo à Instituição - PABLO DE CASTRO SANTOS - UERN
Externo à Instituição - THALES DOMINGOS ARANTES - UNESP