Isolation, purification, and characterization of novel polysaccharides from lotus (Nelumbo nucifera) leaves and their immunostimulatory effects.

In this study, a crude water-soluble polysaccharide (LLWP-C) was extracted from lotus leaves and further purified by size exclusion chromatography, to obtain the two main polysaccharides, LLWP-1 and LLWP-3. Physical and chemical analyses showed that they were homogeneous polysaccharides in β-type glycosidic linkage. LLWP-1 was devoid of helical conformation, had a molecular weight of 85.1 kDa and was mainly composed of Rha, Ara, Gal, Glu, and GalA in a molar ratio of 7.0:24.8:28.0:6.0:26.4. LLWP-3 showed a helical conformation, had a molecular weight of 12.5 kDa and consisted mainly of Rha, Ara, Gal, Glu, Man, and GalA in a molar ratio of 6.6:9.8:15.0:8.9:6.1:47.2. It was demonstrated that LLWP-C and both purified LLWP-1 and LLWP-3 could effectively enhance the proliferation, phagocytosis, nitric oxide (NO), and cytokine secretions by activating corresponding mRNA expression in macrophages, via MAPK and NF-κB pathways. LLWP-3 displayed the greatest immunostimulatory potential, followed by LLWP-1 and LLWP-C. These findings suggest that polysaccharides extracted from lotus leaf exert immunostimulatory activity that could be further investigated to develop functional foods and natural immunopotentiating therapeutic agents.