Objective: To analyze the compositions of polysaccharides in Maca obtained by step alcohol precipitation

and study their antioxidant capacity respectively.Method: The crude Maca polysaccharides were obtained by water extraction and alcohol precipitation method

then separated and purified by step alcohol precipitation. Gas chromatography (GC) was used to analyze the monosaccharide compositions of Maca polysaccharides. Finally

their antioxidant capacity was studied by trichloroacetic acid method and DPPH free radical scavenging method.Result: 0-40% Ethanol polysaccharide

40%-50% ethanol polysaccharide

50%-60% ethanol polysaccharide

60%-70% ethanol polysaccharide and 70%-80% ethanol polysaccharide were obtained as ethanol concentration was increased by fractional precipitation

and they were named as MP1

MP2

MP3

MP4 and MP5 respectively. Among them

MP1 had the highest yield (0.856%) and MP4 had the highest purity (68.5%). Gas chromatography results showed that the compositions of Maca polysaccharides including the type and ratio of monosaccharides were different under different ethanol concentrations. Antioxidant capacity test results showed that the antioxidant capabilities of different polysaccharide fractions were obviously different

among which MP5 had the strongest antioxidant capacity

followed by MP4

and MP1 had the weakest antioxidant capacity.Conclusion: There was great difference in antioxidant activity for various Maca polysaccharides fractions

and that was related to the type

proportion and spatial conformation of their monosaccharide compositions. The step alcohol precipitation had important significance for the separation and purification of Maca polysaccharides

and it could provide a reliable reference for the further studies on purification

structure and pharmacology of Maca polysaccharides.