Sulfonation of (1→6)-β-D-Glucan (Lasiodiplodan) and Its Antioxidant and Antimicrobial Potential

The objective of this study was to investigate the sulfonation of (1→6)-β-D-glucan (lasiodiplodan) as a potentiating mechanism for biological functionalities. Lasiodiplodan was sulfonated by the chlorosulfonic acid-pyridine method. The modified exopolysaccharide was characterized by FT-IR and 13C NMR spectroscopy, X-ray diffraction and SEM. Antioxidant activity was assessed by the methods of H2O2 and OH radical removal and reducing power. Antimicrobial potential was evaluated by the broth-microdilution method. Sulfonation resulted in a derivative with DS of 0.24. FT-IR analysis indicated the introduction of sulfonyl groups in the macromolecule structure through specific bands in the regions of 1,240 cm-1 and 810 cm-1. 13C NMR analysis suggested that sulfonation occurred at carbon 2 of the glucose residue. Sulfonation led to morphological changes in the structure of the biopolymer resulting in a heterogeneous structure with the presence of fibrils. Derivatization promoted an increase in the antioxidant ability of the macromolecule, with a high OH removal potential (74.32%). Bacteriostatic activity against E. coli (Escherichia coli) and S. enterica (Salmonella enterica) typhimurium and fungicidal activity against C. albicans (Candida albicans) and C. tropicalis (Candida tropicalis) were found in the sulfonated sample. Sulfonation potentiated the antioxidant and antimicrobial activities of the biomacromolecule, suggesting that it is a potentiating mechanism of biological functions.