Physicochemical properties and in vitro bioactivities of polysaccharides from lotus leaves extracted by different techniques and solvents

The present study aimed to investigate the effect of four kinds of extraction technologies and three solvents on the chemical and biological functions of water-soluble polysaccharides from lotus leaves (LLPs). Results revealed that the yields, basically chemical compositions, molecular weight distributions, compositional monosaccharides, FT-IR spectra, and apparent viscosities of LLPs varied by different technologies, especially by different solvents. All LLPs from lotus leaves possessed obvious biological properties, including antioxidant abilities and inhibitory effects against digestive enzymes. Especially, the lower molecular weight distribution and higher content of uronic acids were observed in polysaccharides extracted by deep eutectic solvent (DES) assisted extraction and DES-microwave assisted extraction, respectively, which might contribute to their stronger antioxidant abilities and inhibitory effects against digestive enzymes. Furthermore, the strong biological activities of alkali extracted polysaccharides were also closely associated with its low molecular weight and high content of proteins. Besides, polysaccharides extracted by pressurized water extraction exhibited strong bioactivities than that of LLPs extracted by other extraction technologies. These findings could provide fundamental knowledge to choose suitable processes for preparing LLPs with desired biological functions and extend the application of polysaccharides from lotus leaves in the functional food industry.