Polissacarídeos sulfatados da alga marrom Dictyota mertensii: avaliação do efeito antioxidante sinérgico em associação com o ácido ascórbico e purificação de uma fração

Abstract

Seaweed are organisms with great biological diversity and wide geographicol distribution. Considering of avaliability, they are important for several areas of knowledge, such as environmental, economic and scientific. They have several organic compounds with bioactive functions, and among these are sulfated polysaccharides (SP). The brown seaweed SP (fucans and fucoidans) have several activities, including antioxidant activity, which may be enhanced by the presence of other antioxidants The antioxidant potential of PS obtained from D. mertensii is already reported in the literature. However, this is below what is found in other PS. Thus, the objective is to evaluate the synergistic effect of antioxidant activity in combination with ascorbic acid. The algal were collected SP from Potiguar coast and submitted to proteolysis and differential acetone fractionation to obtain PS, which led to obtaining 6 fractions (F0.3; F0.5; F0.7; F1.0; F1.5; F2.1). Polysaccharide fractions were subjected to chemical and physical analyzes to determine their composition and as a result, D. mertensii synthesizes structurally different PS. It was observed that the fractions are rich in heteropolysaccharides, with predominance of monosaccharides fucose, glucuronic acid and xylose in the fractions F0.3, F0.5, F1.0, F1,5 e F2.0. In addition to these monosaccharides, glucose and galactose was observed in F1.0 and F1.5. The F0.7 fraction is composed mainly of fucose and glucuronic acid. Three patterns of electrophoretic migration were observed in fractions: a slower profile was observed in fractions F0.3, F0.5 and F0.7; an intermediate profile in F1.0 and a faster profile in fractions F1.5 and F2.1. Different values were also observed for the quantification of total sugars and sulfate in fractions. A higher percentage of sugars was observed in fractions F0.7 and F0.5, with 85% and 66%, respectively, and higher sulfate percentages were observed in fractions F1.0 and F0.7, with 40.2% and 32%, respectively. Fractions were evaluated for antioxidant potential in combination with ascorbic acid in in vitro and cell culture tests. As a result, there was an increase in antioxidant potential from the synergistic effect of PS and ascorbic acid in all fractions, with emphasis on F0.7, in which potentiation of over 100% in total antioxidant capacity and 40% in reducing power activity. The analysis of cell viability in dog renal epithelial cells (MDCK) by the 3- (4,5-dimethyl-thiazol-2-yl) -2,5- diphenyltetrazolium bromide reduction assay (MTT), It was possible to observe decreased cell viability only with the use of fraction F1.5, and F1.0 and F2.0 at a concentration of 1 mg / mL The potential synergistic effect on antioxidant activity in cell culture was evaluated by the hydrogen peroxide induced oxidative stress model in MDCK cells. As a result, a protective effect was observed only with fractions F0.5, F0.7 and F1.0, evaluated separately. The F0.7 fraction was chosen for the purification steps and after the use of ultracentrifugation, ion exchange chromatography and gel filtration chromatography (HPLC) devices, the analyzes showed that F0.7 is composed of three main PS populations. The data found here open the way for further studies to propose the structure of at least one PS, as well as better understand the synergistic effect of these polysaccharides with ascorbic acid.