红曲霉菌胞外多糖的分离纯化、结构鉴定及抗氧化活性测定

目的:分离纯化红曲霉菌胞外多糖（Exopolysaccharide,EPS）,测定各组分的抗氧化活性并对其结构进行初步表征。方法:红曲霉菌发酵液经乙醇沉淀获得胞外多糖,经精制除杂和DEAE-纤维素柱层析法分离纯化获得多糖组分,再分别用高效凝胶过滤色谱法（HPGFC）、柱前衍生PMP-HPLC法测定相对分子质量（Mw）和单糖组成,测定多糖组分清除DPPH和羟自由基的能力,评价其体外抗氧化活性。结果:EPS经分离得到三个组分EPS-1、EPS-2和EPS-3,相对分子质量分别为8673、143537、238742 Da。EPS-1、EPS-2均由甘露糖、鼠李糖、葡萄糖、半乳糖组成,摩尔比为1∶0.301∶2.052∶3.614和1∶2.475∶1.950∶1.532,EPS-3由甘露糖、鼠李糖、葡萄糖醛酸、葡萄糖、半乳糖组成,摩尔比为1∶0.401∶0.066∶0.307∶2.974。三个多糖组分对DPPH·和羟自由基均有清除能力,并与多糖浓度呈现正相关。当多糖浓度为1 mg/m L时,三个组分对DPPH清除率分别为16.4%、15.9%和14.8%;对清除羟自由基的清除率分别为40.4%、39.6%、63.8%。结论:红曲霉菌胞外多糖各组分的相对分子质量和单糖组成比例均有差异;对羟自由基、DPPH·的清除作用也存在差异,这种活性差异可能与各组分Mw及结构差异相关。 

Isolation and purification,structure identification and antioxidant activity of Monascus purpureus exopolysaccharide

Objective: To isolate and purify the crude Monascus purpureus exopolysaccharide (EPS) and study the structure identification and antioxidant activity of the exopolysaccharide fractions. Method: The crude polysaccharide was extracted by liquid fermentation and purified by DEAE-cellulose.Molecular weights (Mw) of exopolysaccharide fractions were determined by high performance gel permeation chromatography (HPGPC) and the monosaccharide compositions were determined then by HPLC using precolumnderivatization with 3-methyl-1-phenyl-5-pyrazolone (PMP) separately.The ability of scavenging DPPH and hydroxyl free radical of polysaccharide fractions was tested to evaluate the antioxidant activity. The findings showed that three fractions (EPS-1, EPS-2, EPS-3) were obtained and molecular weights (Mw) were 8673, 143537, 238742 Da respectively.Both EPS-1, EPS-2 were composed of mannose, rhamnose, glucose and galactose with a molar ratio of1∶ 0.301∶ 2.052∶ 3.614 and 1∶ 2.475∶ 1.950∶ 1.532, EPS-3 were composed of mannose, rhamnose, Glucuronic acid, glucose and galactose in a molar ratio of 1 ∶ 0.401 ∶ 0.066 ∶ 0.307 ∶ 2.974. The ability of removing DPPH and hydroxyl free radicals of polysaccharide fractions were positively related with concentrations. When it was up to 1 mg/m L, the DPPH clearance rate turned out to be 16.4%, 15.9% and 14.8% respectively, hydroxyl free radical clearance rate of EPS-3 was 63.8%, and EPS-1, EPS-2 was 40.4% and 39.6% respectively. Conclusion: There existed some difference in monosaccharide composition and relative molecular mass and the ability of scavenging hydroxyl free radical and DPPH scavenging ability among EPSs, which could be associated with Mw and their structures.