Síntese verde de nanopartículas de prata a partir de polissacarídeos sulfatados de Gracilaria birdiae e caracterização de sua atividade antioxidante

Abstract

Sulfated polysaccharides (SPs) from the edible red algae Gracilaria birdiae have antioxidant activity. Previous study have shown that these SPs, when in the form of silver nanoparticles (AgNps), showed better antioxidant activity than in its original form. However, there is no data about AgNps synthesized with the SPs from G. birdiae. Then, AgNps synthesized with the SPs from G. birdiae were obtained and evaluated as antioxidant agents. For this, the seaweed were collected, frozen, cleaned, dried, crushed, weighed, defatted and dried again. After that, they were proteolysed and centrifuged. The resulting supernatant was mixed with methanol to promote the polysaccharides (PS) precipitation. After 24 h, these PS were separated from the solution by centrifugation, dried, solubilized in distilled water and placed to react with silver nitrate per 24 h, under stirring. The AgNps detection and size measurement were made by dynamic light scattering (DLS). The PS reducing capacity was evaluated by the total antioxidant capacity test (TAC). The antioxidant capacity of AgNps and SPs was also determined by ferric chelation test. In addition, their protein and sugar content were determined spectrophotometrically. The PS showed TAC, and this allowed the synthesis of AgNps. The AgNps showed an average size of 117.6 nm. No protein contamination was found in the SPs neither AgNps. The sugar content in the AgNps suspension was higher (55.7%) than that found in the SPs solution (49.7%). The AgNps suspension presented an iron chelating activity 25% higher than the of SPs solution. The results showed that the SPs of G. birdiae, in the form nanoparticles, had their iron chelating activity enhanced, indicating that the silver nanoparticles can be subject of further studies to identify their potential as antioxidants agents in different applications.