Comparison of physicochemical properties and biological activities between two acidic sugarcane leaf polysaccharides

Sugarcane leaves are a common waste product of sugarcane but contain various active components. To make full use of the value of sugarcane leaves, it shall be urgently developed as a sustainable resource. To compare the differences in structure and activity between acidic sugarcane leaf polysaccharides (ASLs) extracted by different extraction methods, ASLW and ASLM polysaccharides were extracted using hot alkali extraction (HAE) and microwave-assisted hot alkali extraction (MHAE), respectively. The physicochemical properties were analyzed with high-performance liquid chromatography, scanning electron microscopy, infrared spectroscopy and X-ray diffraction. Then, the antioxidant, hypolipidemic, hypoglycemic and antibacterial activities of ASLW and ASLM were evaluated by the inhibition of oxygen free radicals, the inhibition of α-glucosidase and α-amylase, the binding ability with bile salts and the filter paper method. Molecular weight and monosaccharide composition analyses showed that ASLW (142.23 kDa) and ASLM (98.86 kDa) were heteropolysaccharides with a wide range of monosaccharide types and molar ratios. ASLM is an amorphous polysaccharide with stronger stability. Also in vitro bioactivity analysis showed that ASLM had stronger antioxidant, hypolipidemic, hypoglycemic and antibacterial effects than ASLW. As a sustainable active substance, the use of ASLM will benefit the pharmaceutical, industrial, agricultural, and food industries.