Acetylation Modification of <i>Lavandula angustifolia</i> Polysaccharides: Physicochemical Property, Antioxidant and Hypoglycemic Activities

Chemical modifications can impart distinct physicochemical properties and biological activities to polysaccharides. In this study, Lavandula angustifolia polysaccharide (LAP) was purified through a series of processes including decolorization, deproteinization, freeze-drying, and column chromatography using DEAE-750 cellulose and Sephadex G-200, yielding a major homogeneous polysaccharide designated as LAP. The LAP was subsequently modified via acetylation method, producing a series of acetylated derivatives with varying degrees of substitution, referred to as LAP-1, LAP-2 and LAP-3, respectively. The characterization of these polysaccharides was conducted using various methodologies, including viscosity, solubility, molecular weight (Mw), ultraviolet (UV), infrared (IR), x-ray diffraction (XRD), Congo red, thermogravimetric (TG), differential thermogravimetry (DTG), and scanning electron microscopy (SEM). The LAP and its derivatives were identified as heteropolysaccharides composed of varying molar ratios of fucose, rhamnose, mannose and galactose, with Mws of 27.32, 19.74, 17.52, and 21.43 kDa, respectively. The acetylation modifications were found to influence the viscosity, solubility, surface morphology and thermal properties of LAP and its derivatives, and notably, these effects were observed to be beneficial. Furthermore, antioxidant and hypoglycemic activity assays demonstrated that acetylation significantly enhanced the biological activities of the polysaccharides, exhibiting a positive correlation with the degree of substitution. These findings suggest that distinct functional and bioactive polysaccharides can be developed through acetylation modification.