Abstract: To optimize the deproteinization process and to determine the neuroprotective activity of Rhizoma Menispermi crude polysaccharide,five methods were compared to screen out the best protein removing method for the Rhizoma Menispermi crude polysaccharide,including enzymatic method,Sevage method,enzyme-Sevage method,TCA-n-butanol method and enzyme-TCA-n-butanol method.The effects of the volume ratio of TCA to n-butanol,the ratio of the polysaccharide solution to the TCA-n-butanol solution and the shake time on the deproteinization of Rhizome Menispermi crude polysaccharide in TCA-n-butanol method were investigated by single-factor experiment combined with central combination design method of Box-Behnken.PC12 cell injury was induced by H₂O₂ to study the neuroprotective activity of Rhizoma Menispermi crude polysaccharides.The results showed that the best method for deproteinization process of Rhizoma Menispermi crude polysaccharide was TCA-n-butanol method.The optimal conditions were as follows∶the ratio of TCA to n-butanol was 1∶10.4,the ratio of solution of Rhizoma Menispermi crude polysaccharide to TCA-n-butanol solution was 1∶1.77,and the shaking time was 36.5 min.Under this condition the remove rate of protein was 73.1 %,the comprehensive score was 92.1.Neuroprotective studies have showed that Rhizoma Menispermi crude polysaccharide has obvious protective effect on H₂O₂-induced PC12 cell injury.This study showed that the TCA-n-butanol method can effectively remove the protein in the Rhizoma Menispermi crude polysaccharides,and the Rhizoma Menispermi crude polysaccharides had neuroprotective activity.

Key words: Rhizoma Menispermi crude polysaccharide, deproteinization process, TCA-n-butanol method, response surface method, neuroprotective activity