| In recent years, plant polysaccharides has aroused widespread concern, becauseit has much of pharmacological activity, which is closely related to the maintenanceof vital functions. Hops have a thousand years of application history, and has varietyof pharmacological activity and efficacy of the bitter resin, polyphenols, flavonoids,but the activity of the hops polysaccharide is still blank. Hops is an importanteconomic crop in Xinjiang, with the annual production of about6000tons or more. Itmainly uses most of the fat-soluble bitter ingredients and flavor components in theprocessing of hops, the rest of hops is used for waste disposal, and ingredient of hopspolysaccharides is basically kept in waste. This paper, with hop extract residue as rawmaterial, based on the investigation on composition and distribution of hopspolysaccharides, evaluated the antioxidant activities of each component of hopspolysaccharides. Then, protein and pigment were removed from crude extracts ofhops polysaccharide, and crude hops polysaccharide were further separated andpurified, which determined the basic configuration and primary structure of thepolysaccharide, the monosaccharide composition and proportion as well.Sugar compounds of hops were extracted by using the traditional hot waterextraction method. The extraction ratio, content of sub-step and grade ethanolprecipitation of polysaccharides from hops were analyzed and discussed, henceconfirming the content distribution of hops polysaccharides.The optimal extraction processing parameters were investigated by orthogonalexperiments combined with single factor experiments. The best technologicalconditions for hot distilled water extraction by microwave-assisted include theextraction time of2h, ratio of solid-liquid1:10, extraction temperature of90℃andmicrowave power for12min, under which condition the yield of polysaccharidesfrom hops is up to2.76%. Protein removal rate and polysaccharide retention rate wereused to evaluate and compare the effectiveness of several methods. Bromelain-TCA-n-butanol was found to be the best method for the deproteinizationof hop crude polysaccharides. But compared with the loss rate of polysaccharide, thepapain-hydrochloric acid-n-butanol method was better.Preliminary purification polysaccharide sample (HPC) was obtained from crudehops polysaccharide by water extraction, alcohol precipitation, removal of protein,hydrogen peroxide bleaching and alcohol precipitation again. After the purified thehops polysaccharide sample (HPC1a) was obtained by DEAE-cellulose column,dialysis, step-by-step alcohol precipitation, purity and content of HPC and HPC1awere evaluated. Then HPC1a was analyzed by infrared spectroscopy, ultravioletspectroscopy, thin layer chromatography and PMP pre-column derivative by highperformance liquid chromatography method. The results show that hopspolysaccharide may be a β-pyranose, containing uronic acid but polyphenols,proteins, nucleic acids, reducing sugars and other ingredients; and the containedmonosaccharides is mainly composed of D-arabinose, D-galactose, L-(-)-fucose,L-rhamnose, D-mannose, D-galacturonic acid and D-glucuronic acid, with the molarratio of10.77:3.91:2.19:0.33:0.20:0.31:0.57.The antioxidant activities of sub-step and grade ethanol precipitation ofpolysaccharides from hops were assessed by DPPH free radical scavenging assay,Hydroxyl radical-scavenging activity assay, β-Carotene-linoleic acid oxidationinhibitory activity assay, reducing power and Nitrite-scavenging activity assay. Theresults showed that the the hops polysaccharide has demonstrated some antioxidantactivity in different antioxidant systems. Among them, β-Carotene-linoleic acidoxidation inhibitory activity assay, Hydroxyl radical-scavenging activity assay andNitrite-scavenging activity assay of hops polysaccharide were relatively strong, whilethe reducing power and DPPH radical scavenging assay were relatively weak. Besides,with the decreasing weight of molecular, its antioxidant capacity apparently increased. |
PDF Full Text Request