(1→6)-β-D-glucana (Lasiodiplodana) sulfatada: obtenção, caracterização e propriedades bioativas

Abstract

Lasiodiplodan is a fungal (1→6)-β-D-glucan which exhibits different biological functionalities, including antioxidant, hypocholesterolemic, hypoglycemic and anticarcinogenic activities. Their biological properties may be potentiated by chemical modifications in the macromolecule structure, such as sulfation. In this context, sulfate derivatives with different degrees of substitution (DS) were obtained and characterized by Fourier Transform Infrared Spectroscopy (FT-IR), Scanning Electron Microscopy (SEM), Thermal Analysis (DTG, TGA and DTA), X-ray Diffraction (XRD) and solubility. Biological properties were evaluated, including antimicrobial (MIC) and antioxidante (FRAP, OH, ABTS and DPPH) activities and cytotoxic potential. Sulfated derivatives with different DS (1.61, 1.42, 1.02 and 0.15) were obtained, and there was no direct correlation between DS and the concentration of the sulfating reagent used in the derivatization protocol. Derivatization promoted an increase in the solubility of the macromolecule regarding to native lasiodiplodan. Sulfation was confirmed by FT-IR through the emergence of bands at 1250 cm-1 (S=O) and 810 cm-1 (C-O-S), derived from the introduction of sulfonic groups. SEM showed that sulfation promoted morphological changes on the surface of the biopolymer, leading to the appearance of heterogeneous fibrillar structures along the surface area. The sulfated lasiodiplodan showed higher thermal stability (oxidation temperatures close to 460 °C). XRD analysis demonstrated that the native and sulfated lasiodiplodan samples present a predominantly amorphous diffractographic profile, characteristic of polysaccharides. Sulphation enhanced the antimicrobial activity of lasiodiplodan, especially against Candida albicans (fungicidal activity) and Salmonella enterica Typhimurium (bacteriostatic activity). The native sample presented higher hydroxyl radical removal capacity, while the sulfated derivatives showed higher FRAP potential. Native and sulfated lasiodiplodan did not demonstrate lethal cytotoxicity against wild and mutants Saccharomyces cerevisiae strains at the concentrations studied. Samples with higher DS (1.42 and 1.61) had lower potential for induction to oxidative stress. The results of the present study indicate that the sulphation process can be an attractive tool to improve the lasiodiplodan biological activities and could contribute to the diversification of its biotechnological applications.