Effects of Astragalus Polysaccharides with Different Molecular Weights on Calcium Oxalate Crystal Growth and Cytotoxicity

The elects of four astragalus polysaccharides (ASPO, ASP1, ASP2 and ASP3) with carboxylic group (- COOH) content of 16.7%(w/w) but molecular weights of 11.0, 8.4, 4.7 and 2.6 kDa, respectively, on the formation of calcium oxalate (CaOx) crystals were comparatively studied. X - ray diffraction (XRD), Fourier transform infrared spectroscopy (FT - IR) and scanning electron microscopy (SEM) results revealed that all the four ASPs inhibited COM growth, induced COD formation. The inductively coupled plasma emission spectra (ICP) revealed that these ASPs increased the concentration of soluble Ca2+ ions in the solution and reduced the amount of CaOx precipitation. Furthermore, ASPs increased the absolute value of zeta potential on the crystal surface, and thus inhibited crystal aggregation. The ability of ASPs to regulate CaOx crystal formation and induce COD formation is negatively related to its molecular weight, that is, ASP3 with the smallest molecular weight has the strongest regulatory ability. In addition, each ASPs is not only toxic to HK-2 cells, but also can repair oxalate-damaged HK-2 cells and decrease cellular ROS level, of which APS2 with moderate molecular weight showed the best repair ability.