Banca de DEFESA: JOICY RIBEIRO DOS SANTOS

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : JOICY RIBEIRO DOS SANTOS
DATE: 21/09/2025
TIME: 08:30
LOCAL: Videoconferência
TITLE:

CONJUGATION OF FUCOIDAN B FROM THE ALGA Spatoglossum schröederi WITH GALLIC ACID AND EVALUATION OF ITS ANTIOXIDANT ACTIVITY IN VITRO, IN CELLS (MURINE FIBROBLAST L929) AND IN VIVO (Danio rerio)

KEY WORDS:

Sulfated polysaccharides; fucoidans; brown seaweeds; oxidative stress

PAGES: 105
BIG AREA: Ciências Biológicas
AREA: Bioquímica
SUMMARY:

Oxidative stress is responsible for a wide range of health problems. In recent years, the scientific community has been constantly searching for molecules that can prevent the formation of reactive oxygen species (ROS), their accumulation in the body, and/or mitigate the damage they cause. Fucoidans are sulfated polysaccharides (SP) found exclusively in brown seaweeds, known for their various pharmacological activities, such as anticoagulant, anti-inflammatory, and antioxidant effects. Moreover, chemical modifications of these SPs can enhance such activities. In this study, fucoidan B from the brown seaweed Spatoglossum schröederi was obtained, chemically conjugated with gallic acid (GA), and evaluated for its antioxidant activity both in vitro and in vivo. The resulting compound, named FucB-GA, was physiochemically characterized. The results showed that FucB-GA has a molecular weight of 22.8 kDa, contains 3% phenolic compounds, and exhibits no protein contamination. FT-IR and ¹H NMR analyses confirmed the incorporation of GA into the polymeric chain. FucB-GA displayed changes in amorphous characteristics as well as in thermal stability compared to native FucB. In the in vitro antioxidant assays, FucB, FucB-GA, and GA were not able to chelate Fe²⁺; however, FucB-GA exhibited superior Cu²⁺ chelation compared to FucB. Regarding radical scavenging, no statistically significant differences were observed for H₂O₂ scavenging. FucB-GA achieved a 91.96% superoxide radical scavenging capacity, compared to 80.51% for FucB. In terms of electron-donating capacity, FucB-GA showed approximately threefold higher activity than FucB in the total antioxidant capacity (TAC) assay, and about fourfold higher activity in reducing power. In all in vitro antioxidant tests, GA alone did not show activity. Cell-based assays demonstrated that FucB-GA was able to reverse oxidative stress-induced damage, both in concomitant and reparative effects, under H₂O₂ exposure. In the animal model Danio rerio, FucB-GA increased embryo survival after stress and reduced ROS production. Altogether, the results demonstrate that the chemical modification enhanced the antioxidant capacity of FucB-GA, highlighting its potential as a promising antioxidant molecule for future applications.

COMMITTEE MEMBERS:
Externo à Instituição - DIEGO DE ARAUJO SABRY - IFPI
Presidente - 2195251 - HUGO ALEXANDRE DE OLIVEIRA ROCHA
Externa à Instituição - KAROLINE RACHEL TEODOSIO DE MELO - FACENE
Externo ao Programa - 3060683 - LEONARDO THIAGO DUARTE BARRETO NOBRE - nullExterna à Instituição - VALQUIRIA PEREIRA DE MEDEIROS - UFJF