Abstract: Algal eucheuma striatumsulfated polysaccharide (ESPS) collected from Indonesian sea was degraded by hydrogen peroxide (H2O2).After degradation the averagemolecularweight of ESPSwas decreased from1410000 to 4819, and the content of sulfate (OSO2-3) was lightly decreased from 16.0%to 15.2% (w). The effect of ESPS before and after degradation on the growth of calcium oxalate crystal was investigated in vitro by using scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. Compared with the undegraded ESPS, the size and number of calcium oxalatemonohydrate (COM) crystal induced by the degraded ESPS weremuch smaller.With increasing the concentration of degraded ESPS from0.006 g·L-1 to 0.010 and 0.050 g·L-1, the average size of COMcrystals decreased from 11.5 μm×2.9 μm to 9.2 μm×2.9 μm and 6.0 μm×2.5 μm, respectively, and the number of COM crystals decreased from 3357 per mm2 to 2298 and 1532 per mm2, and the diffraction peak intensity ratio of the (101) plane to (010) plane of COM crystals (I(101)/I(020)) increased from5.54 to 16.2 and 20.0. The result showed that the inhibition efficiency of the degraded ESPS with a low-molecular-weight on the nucleation and growth of CaOxa crystal was obviously superior to that of the undegraded ESPS.

Key words: Algal eucheuma striatum, Low-molecular-weight polysaccharide, Degradation, Urolithiasis, Calciumoxalate