Studies On The Extraction, Purification And Bioactive Functionality Of The Garlic Polysaccharide

Garlic(Allium sativum L) is a dual-purpose plant resource of herb and food, which is planted extensively in China.Garlic bulb,what is called garlic,contains many kinds of nutritive elements and has many pharmacological actions.The polysaccharides extracted from garlic is one of the bioactive components,which have many biological activities,such as immune regulation,anti-tumor effect,anti-virus effect and hypoglycemic effect.In this paper,the polysaccharides extracted from garlic was studied.On the basis of systematic analysis on the extraction,isolation, purification and primary structure of the polysaccharides,its antioxidant activity and functional properties were studied preliminarily.The main research contents and conclusions were as follows:An anthrone-sulfuric method was developed for the determination of garlic polysaccharides.Purified polysaccharides in garlic was prepared by extracting with water and removing the interference components such as lipid,monosaccharide, disaccharide and protein.A corrected factor was confirmed by comparing purified polysaccharides with glucose in order to minimize the error of determination. Anthrone-sulfuric method was used to test the content of garlic polysaccharides and the conditions of colour reaction of anthrone-sulfuric method were also optimized. The experiment results showed that:The RSD in accuracy experiment was 2.1%,the average recovery rate was 113%,with RSD=1.17%(n=3),operating condition was: anthracenone reagent was added in the ice water bath,heating 8min in the condition of 100℃,after cooling to room temperature rapidly by tap water,the absorbance value that was tested in 10min at 585nm can be trusted.Polysaccharides in dry garlic powder were extracted by hot water.The effects of main factors such as comminution degree,extraction temperature,extraction times, extraction time,ratio of material to water were investigated.A L₉(3³) orthogonal experiment was carried out by taking extraction temperature,ratio of material to water,extraction time as the parameters.The optimal experimental parameters were extraction temperature 80℃,rate of material to water 1:30(m/v),extraction time 150min.The yield of garlic polysaccharides was 36.10%.Protein in the crude garlic polysaccharides was removed by TCA method,sevag method and enzyme combined with sevag method.By comparing the removal percentage of protein and the recovery rate of polysaccharides,it was found that the removal percentage of protein by enzyme combined with sevag method is lower than TCA method,but higher than sevag method and the recovery rate of polysaccharides is the highest.Comprehensive consideration,enzyme combined with sevag method is a reasonable method.The primary purification of the garlic polysaccharides were carried out by DEAE-52 cellulose chromatography.GP-2 and GP-3 were mainly obtained in this process,and they were purified with Sephadex G-200 column chromatography furtherly.The results showed that both of them have a single elution peak,which implied that GP-2 and GP-3 have a high purity.The molecular weight of GP-2 and GP-3 was about 12379Da and 33865Da,which were determined by high-performance gel permeation chromatography(HPGPC).The monosaccharide composition of polysaccharides GP-2 and GP-3 were analyzed by gas chromatography.They were mainly composed of Ara,Xyl,Man,Glu and Gal.Infrared spectrum of polysaccharides GP-2 and GP-3 indicates that they had typical characteristic absorption peaks.The antioxidant effects of different garlic polysaccharides(GP,GP-1,GP-2) were studied in vitro by different testing model,which included oil antioxidant model, DPPH free radical scavenging model,superoxide anion radical and hydroxyl radical model.The results showed that GP,GP-1 and GP-2 all had certain antioxidant activities.The correlativity of their effects and the dose are positive,in a certain concentration range.The GP showed the highest antioxidant activities in these three components.