Structural Elucidation and Antioxidant Activity of LRP-Ⅰ and LRP-Ⅱ Polysaccharide from Leccinum rugosiceps

Two main polysaccharide fractions(LRP-Ⅰ and LRP-Ⅱ)were isolated from Leccinum rugosiceps fruit by hot water extraction. The structural characterstics of LRP-Ⅰ and LRP-Ⅱ were elucidated by chromatographic methods,and the difference of antioxidant activity between the two polysaccharides was also evaluated in this paper. Infrared spectromete(IR)showed that LRP-Ⅰ and LRP-Ⅱ were α-pyranohexose with characteristic peaks of polysaccharides. The monosaccharide compositionwas determined by high performance liquid chromatography(HPLC),LRP-Ⅰ mainly consisted of mannose,rhamnose,glucose,xylose and fructose in a molar ratio of 0.68:0.10:2.87:0.28:0.12,and LRP-Ⅱ was mainly composed of mannose,glucose,xylose,alabinoseand fructose in a molar ratio of 1.69:2.30:2.06:0.10:1.04. The average molecular weights of LRP-Ⅰ and LRP-Ⅱ respectively were 1.98×10⁴ Da and 8.38×10⁶ Da by high performance gel-permeation chromatography(HPGPC).The methylated derivatives were analyzed by gas chromatography-mass spectrometer(GC-MS),the results suggested that→1,4)-Glcp,→1,3)-Manp and →1,3)-Xylp bond types existed in the both of LRP-Ⅰ and LRP-Ⅱ molecules.The scanning electron microscope(SEM)illustrated that scattered flaky,banded and filiformpolysaccharide existed in LRP-Ⅰ,differently reticular structure dominated in LRP-Ⅱ. In the content of 1~10 mg/mL,antioxidant experiments demonstrated that both of LRP-Ⅰ and LRP-Ⅱ showed the good scavenging effects on ABTS radical and DPPH radical,especially LRP-Ⅰ was slightly stronger in scavenging rate than that of LRP-Ⅱ. This study provides a reference for further understanding the polysaccharide activity mechanism of Leccinum rugosiceps.