Purfication,Characterization And Partial Biological Activity Of Polysaccharides From Stem Lettuce(Taigan)

Lettuce(Lactuca sativa Linn.)is a genus of the genus Compositae,a traditional vegetable variety that is nutritious and popular.Stem lettuce is one of the varieties of lettuce.Its stems are rich in carbohydrates.In order to further develop and utilize stem lettuce resources,stem lettuce(Taigan)is used as a raw material in this paper and single factor experiments are used in combination.The response surface design optimizes the hot water extraction process of stem lettuce polysaccharide(SLP),and on this basis,the antioxidant activity and basic physicochemical properties of the extracted polysaccharide are analyzed.The lettuce polysaccharides were further isolated and purified.The in vitro immunological activity and basic physiochemical properties of the purified components were studied.The results obtained are as follows:1.The extraction temperature,extraction time and ratio of liquid to material are important affecting factors for the extraction rate of SLP,and the effect of the extraction temperature > extraction time> ratio of liquid to material.The optimized extraction process parameters after optimization of the response surface design were as follows: extraction temperature 95℃,extraction time 3.3 h,and extraction liquid-to-feed ratio 25 mL/g.Under this condition,the extraction rate of lettuce polysaccharides was 20.89%.2.Determination of the total sugar content of SLP and its purified components SLP-1 and SLP-2 were 67.53%,81.7% and 86.3 respectively;the protein content of SLP was 1.87%.The purified components SLP-1 and SLP-2 contain almost no protein and other impurities,which was consist with the results of UV scan.The Fourier transform results showed that the SLP and their purified components were all sulfated polysaccharides,and all contained characteristic absorption peaks of the polysaccharides and all had a triple helix structure.The molecular weights of SLP-1 and SLP-2 are 90 kDa and 40 kDa,respectively.The results of monosaccharide composition showed that SLP was mainly composed of mannose,ribose,rhamnose,galacturonic acid,glucose,galactose,and arabinose,and their molar ratio was 1.2:1.6:1.0:49.2:0.8:23.3,respectively: 22.9;while SLP-1 is mainly composed of mannose,rhamnose,galacturonic acid,galactose,and arabinose in a molar ratio of 3.6:3.2:17.6:41.7:33.9;SLP-2 is mainly composed of mannose,Composition of rhamnose,galacturonic acid and arabinose,molar ratio 11.5;1.45;69.5;9.3;3.The SLP have strong DPPH radical,superoxide anion radical,hydroxyl radical scavenging activity and strong metal ion chelating ability.It also has a strong inhibitory activity on α-amylase.The results of in vitro cell immunoreactivity showed that SLP-1 and SLP-2 can effectively promote the proliferation of peritoneal macrophages in RAW264.7 mice,and increase their phagocytosis and NO secretion.