O-Acetylated (1→6)-β-D-Glucan (Lasiodiplodan): Chemical Derivatization, Characterization and Antioxidant Activity

Abstract

β-Glucans are biomacromolecules that present biological properties of medical and pharmacological interest. The chemical modification of the primary structure of these carbohydrate biopolymers is a way to enhance or achieve new biological properties. Acetylated derivatives of (1→6)-β-D-glucan (lasiodiplodan) with different degrees of substitution (0.48, 0.66, 1.03 and 1.26) were obtained and characterized by infra-red and NMR (nuclear magnetic resonance) spectroscopy, thermal analysis, X-ray diffraction and antioxidant capacity. Acetylation was confirmed by FT-IR, and 13C NMR spectroscopy. Thermal analysis indicated that unmodified lasiodiplodan and the O-acetylated -glucan derivative of degree of substitution 0.48 presented three stages of mass-loss, whereas acetylated derivatives of DS (degree of substitution) of 0.66, 1.03 and 1.26 presented four stages of mass-loss. X-ray diffractograms demonstrated that both native and acetylated lasiodiplodan presented crystalline regions in an amorphous polymeric matrix. Scanning electron microscopy revealed that O-acetylation promoted morphologic changes in the biopolymer according to the DS. Acetylation also contributed to improve antioxidant capacity.