超高压提取红心火龙果果皮多糖理化特征及抗氧化活性研究

Ultrahigh pressure extraction, physicochemical characteristics and antioxidant activity of polysaccharide from red dragon fruit peel

采用单因素、Box-Behnken design(BBD)试验响应面(RSM)法优化超高压提取(UPE)红龙果果皮多糖(RDFPs)工艺,以提高多糖得率.最佳工艺条件为:提取时间42.75 s,温度51.61℃,压力316.44 MPa;在修订最优条件下RDFPs的实验得率为34.31%,与预测得率(34.5%)一致.用超滤法和Sephadex G-100分子筛凝胶分离得到多糖组分RDFP-1,RD-FP-2,RDFP-3,RDFP-4和RDFP-5,相对分子质量分别为7950,16460,49980,145350和193710,并对它们的理化性质和体外抗氧化活性进行了比较研究.结果表明,RDFPs含有76.84%~84.22%的中性糖,9.64%~18.55%的糖醛酸,0.06%~0.88%的蛋白质.傅里叶红外光谱(FT-IR)和紫外(UV)光谱显示这些组分都具有多糖的特征吸收峰.RDFP-1和RDFP-4对1,1-二苯基-2-苦基肼自由基(·DPPH)、羟基自由基(·OH)和超氧阴离子自由基(·O_(2)^(-))的清除活性显著高于其他多糖组分,这可能与它们较小的相对分子质量和较高含量的糖醛酸有关.这些结果表明,UPE多糖具有得率高、时间短及抗氧化活性显著等优点;RDFP-1和RDFP-4可以探索作为天然抗氧化剂.

An efficient ultra-high pressure extraction(UPE)tech-nology was applied for the polysaccharide(RDFPs)extraction from red pitaya peels(RPPs),contributing to the increase yield and antioxidant activity.The quantitative effects of extraction time(20~120 s),pressure(100~500 MPa),temperature(20℃~70℃)and liquid to material ratio(1∶10~1∶60 g·mL^(-1))on extraction yield of RDFPs were investigated using response surface methodology(RSM)coupled with Box-Be-hnken design(BBD)on the basis of the results of single factor experiments.The results showed that the maximum RDFPs yield of 35.5%was obtained with extraction time 42.75 s,temperature 51.61℃,pressure 316.44 MPa,liquid to material ratio 1∶66.57 g·mL^(-1).Under these conditions,the experimental yield of RDFPs was 34.31%,which is close to the predicted yield of 34.5%,indicating that the established model was accurate and reliable.Five fractions(RDFP-1,RDFP-2,RDFP-3,RDFP-4 and RDFP-5)were successfully purified by ultrafiltration and Sephadex G-100 gel-permeation chromatography.Physicochemical characteristics analysis revealed that RDFPs con-tained 76.84%to 84.22%neutral sugar,9.64%to 18.55%uronic acid and 0.06%to 0.88%pro-tein.The relative molecular mass(Mr)of RDFPs ranged from 7950 to 193710.Fourier transform in-frared(FT-IR)and ultraviolet(UV)spectra showed that RDFP-1,RDFP-2,RDFP-3,RDFP-4 and RDFP-5 all had the general characteristic absorption peaks of polysaccharides,RDFP-1 and RDFP-2 were pyranose containingα-glycosidic bond,RDFP-3,RDFP-4 and RDFP-5 were pyranosyl containingβ-gly-cosidic bonds.The antioxidant activities of 1,1-diphenyl-2-picrylhydrazyl radical(·DPPH),hydroxyl radical(·OH)and superoxide anion radical(·O_(2)^(-))in vitro were compared.Among the five samples,RDFP-1 had the lowest Mr(7950),exhibited the highest·DPPH scavenging activity(92.1%).Mean-while,the Mr of RDFP-5 was the highest and·DPPH scavenging activity was the lowest,indicating that the Mr was negatively correlated with the scavenging activity of·DPPH.The ability of RDFP-4 to scav-enge·OH was significantly higher than that of other polysaccharides,which might be related to its higher contents of uronic acid.