Study on the Extraction and Purification of Polysaccharides from Sugarcane Leaves by Ultrasound-Assisted Enzymatic Hydrolysis and the Antioxidant Activity

This study optimized the ultrasound-assisted enzymatic extraction (UAEE) of polysaccharides from sugarcane leaves and evaluated their structural and antioxidant properties. Response surface methodology was used to optimize the extraction, achieving a high polysaccharide yield of 4.31 ± 0.08%, which significantly surpassed that of conventional methods. Purification yielded two distinct, low-molecular-weight polysaccharide fractions (P-1 at 15 kDa and P-2 at 9.6 kDa). Structural characterization revealed significant differences in monosaccharide composition; P-1 was rich in glucose and xylose, while P-2 exhibited greater structural diversity, including a high content of uronic acid. Both fractions demonstrated dose-dependent antioxidant activities. Notably, P-1 showed superior hydroxyl radical scavenging activity (IC₅₀ = 4.3 mg/mL) compared to P-2 (IC₅₀ = 5.2 mg/mL), whereas P-2 exhibited slightly better DPPH radical scavenging and ferric reducing power. These findings demonstrate that UAEE is a highly efficient method for producing low-molecular-weight, bioactive polysaccharides from sugarcane leaves, which show promise as natural antioxidants for further investigation in functional food and pharmaceutical applications.