Systematic fractionation and immunoenhancement of water-soluble polysaccharides isolated from fruit of Morus alba L.

In this study, we obtained and fractionated systematically the polysaccharides of Fructus mori fruit by the sequential use of water extraction, ethanol precipitation and ion-exchange chromatography. The sugar contents of FPA-1, FPA-2, FPA-4 and FPA-5 were estimated to be 75.70%, 67.15%, 87.78% and 91.63%, respectively. Monosaccharide composition analysis revealed that all the polysaccharides primarily contained Man, GlcA, GalA, Glc, Gal, Xyl, Ara and Fuc. Moreover, a small amount of Rha was detected in FPA-1, FPA-4 and FPA-5. The molecular weight distributions of FPA-1, FPA-2, FPA-4 and FPA-5 were 10.6-49.1 kDa, 22.9-122.7 kDa, 57.1-105.4 kDa and 14.8-19.6 kDa, respectively. According to the in vitro experiment, FPA-1 exhibited the highest activity on enhancing phagocytosis, promoting macrophage to secrete nitric oxide, tumour necrosis factor-α and reactive oxygen species.