Effect of seaweed polysaccharides with different sulfate group contents on crystal growth of calcium oxalate and on the repair of damaged renal epithelial cells

X-ray diffraction, Fourier transform infrared spectrometer, scanning electron microscope, zeta potential analyzer, and inductively coupled plasma emission spectrometer were used to compare the regulation of four degraded seaweed polysaccharides with a similar molecular weight of about 3 700 Da and different contents of sulfate group (-OSO3-) on the inhibition of crystal growth of calcium oxalate (CaC2O4), and the repair ability of the polysaccharides on damaged renal epithelial cells was compared by cell experiments. These four seaweed polysaccharides were degraded Porphyra polysaccharide (PY-1), degraded Gracilaria lemaneiformis polysaccharide (GL-2), degraded Sargassum fusiforme polysaccharide (SF-3) and degraded Undaria pinnatifida polysaccharide (UP-4), and their -OSO3- contents were 17.9%, 13.3%, 8.2%, and 5.5%, respectively. The results showed that these four polysaccharides could inhibit the growth of calcium oxalate monohydrate (COM), induce the formation of calcium oxalate dihydrate (COD), increase the concentration of soluble Ca2+ ions in solution, and increase the absolute value of zeta potential on the crystal surface, thereby reducing the degree of crystal aggregation. In addition, these polysaccharides could repair HK-2 cells damaged by oxalic acid, increase cell viability and superoxide dismutase (SOD) activity, and reduce the release of malondialdehyde (MDA). The results show that the higher the content of -OSO3- in poly-saccharides, the stronger the inhibitory effect of polysaccharides on CaC2O4 crystal growth and the repair effect on damaged HK-2 cells.