Degradation of sulfated polysaccharide extracted from algal Laminaria japonica and its modulation on calcium oxalate crystallization

Sulfated polysaccharide (LPS) extracted from alga Laminaria japonica was degraded by hydrogen peroxide (H2O2). The average molecular weight of LPS was apparently decreased from 172,000 to 9550 after degradation, while the proportion of sulfate groups (–OSO3−) and carboxylic groups (–COO−) in the molecular chains of LPS were slightly decreased from 4.5% and 5.20% to 3.9% and 4.64%, respectively. The effects of degraded and natural LPS on formation of calcium oxalate (CaOxa) crystals were investigated in vitro using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), zeta-potential, and atomic absorption spectroscopy. LPS could increase the concentration of soluble Ca2+ ions in the solution, decrease the weight of precipitated CaOxa, and increase the negative value of zeta-potential of CaOxa crystals. LPS also inhibits the formation of thermodynamically stable calcium oxalate monohydrate (COM) crystals, while inducing and stabilizing metastable calcium oxalate dihydrate (COD) crystals. These results suggested that both degraded and natural LPS could decrease CaOxa crystallization, but the inhibition efficiency of the degraded LPS was clearly superior to that of the natural LPS. We expected this investigation would provide encouragement for further exploration into new drugs for the prevention and treatment of urolithiasis.