Characterization and biological activity of acidic sugarcane leaf polysaccharides by microwave-assisted hot alkali extraction

As a waste of sugarcane, the added value of sugarcane leaves has not been fully utilized, and sugarcane leaf polysaccharide is an important active component of sugarcane leaves. Using new extraction methods to study the structure and biological activity of polysaccharides from sugarcane leaves is of great significance for the development and application of sugarcane leaves. To determine the structural characteristics and biological activities of different acidic sugarcane leaf polysaccharides (ASLPs) extracted by microwave-assisted hot alkali extraction (MALE), three new acidic sugarcane leaf polysaccharides (ASLP-50, ASLP-70 and ASLP-90) were precipitated by ethanol. The structure of ASLPs extracted by MALE contains protein, sulfate and uronic acid. ASLP-50 (195.88 kDa), ASLP-70 (94.62 kDa) and ASLP-90 (16.37 kDa) were acidic polysaccharides composed of mannose, galacturonic acid, glucose, arabinose and fucose. The results of XRD and NMR showed that ASLPs were amorphous polysaccharides composed of α-L-Araf-(1→ main chain, and its branching points were composed of Arap and GalpA residues. In addition, ASLPs showed significant antioxidant, hypoglycemic, hypolipidemic and antibacterial activities in vitro. The research and application of ASLPs provide a reference for the recycling of sugarcane leaves, which is conducive to the development of food, agriculture and pharmaceutical industries.