Study On Extraction And Antioxidant Activity Of Pleurotus Nebrodensis Polysaccharides

Pleurotus nebrodensis is a valuable edible fungus.P.nebrodensis polysaccharides(PNPs)have the function of enhancing immunity,anti-oxidation and anti-tumor.It has become a kind of functional food with high utilization value.In this thesis,the effects of three cultivation methods on the growth of P.nebrodensis were studied.The results showed that the central trunk cutting cultivation was easy to manage and suitable for the cultivation of P.nebrodensis.Response surfacemethod was applied to optimize the ultrasonic-assisted extraction process of PNPs.On the basis of single-factor test,the ultrasonic treating time,extraction temperature and the ratio of water volume to raw material weight(W/M ratio)were analyzed and optimized by the Box-Behnken design.The optimized parameters of the ultrasonic-assisted extraction technology were obtained as follow: extraction temperature was 56 ?,ultrasonic treating time was 45 min,W/M ratio was 41:1,extraction frequency was 2 times,and the extraction rate of the PNPs was 12.26%.Compared with the hot water extraction method which was extraction temperature 77 ?,extraction time 190 min,W/M ratio 46:1,extraction frequency 2 times,the extraction rate of the polysaccharides with ultrasonic-assisted extraction method was increased by 44.41%.The results of polysaccharide purification showed thatoptimized purification condition was the 1/3 volume of Sevage agent(chloroform:n-butanol=4:1)was added in polysaccharide solution for 30 min,centrifuged at 3500 r/min for 10 min and repeat 9 times.Under the condition,the purity of polysaccharide was increased to 89.57%.The purified polysaccharide was prepared and the three polysaccharide components,PNPsA eluted with deionized water,PNPsBeluted with 0.1 mol/L NaCl and PNPs celuted with 0.3 mol/L NaCl,were obtained using DEAE-52 cellulose column.The results of antioxidant activities tests in vitro of the PNPs indicates that the hydroxyl racials and DPPH racials scavenging rates of 4 mg/mL PNPs were 98.39% and 60.8%,respectively.The antioxidant activitie of the polysaccharides was PNPsB>PNPs>PNPsA>PNPsC according to ability to remove hydroxyl radicals and DPPH radicals.Supplied of 0.25%,0.5%,1% of PNPs in the diet of Drosophila melanogaster,the half-death phase,the mean life-span and the maximum life-span were increased in different degrees.The results showed that the maximum life-span of female D.melanogaster were increased by 10.61% and the maximum life-span of male D.melanogaster were increased by 11.82% in the 1% supplied group.The half-death phase,the mean life-span and the maximum life-span of female were increased by 23.08%,22.77% and 18.24% in the 0.5% supplied group,respectively.The effect of increasing the mean life-span was significance,and the effect of half-death phase and maximum life-span extremely significance.The half-death phase,the mean life-span and the maximum life-span of PNPs increased by 27.86%,21.01% and 20.05% in the 0.5% supplied group,respectively,and the effect of the mean life-span was significance,and the effect of half-death phase and the maximum life-span extremely significance.So,the life-span of D.melanogaster was prolonged supplied 0.5% PNPs in medium.The mean body weight and the ability of reverse gravity crawling were increased in different degrees when 0.25%,0.5%,1% of PNPs were supplied in the diet of D.melanogaster,respectively.The female and male D.melanogaster were cultured for 30 days after supplied 0.5% PNPs,the mean body weight was significantly increased by 12.02% and 18.77% and the ability of reverse gravity crawlingwas significantly increased by 44.71% and 34.80% The test of antioxidant activities of D.melanogaster showed that the activities of superoxide dismutase(SOD)and catalase(CAT)were increased in female and male D.melanogaster,and the MDA content decreased in different test group.Comparing with control group,the enzymatic activities of SOD and CAT in D.melanogaster,were increased significantly,and the MDA content decreased significantly in 0.5% dose group.It suggests that PNPs may be increase a series of antioxidant enzyme activity,reduce lipid peroxidation,to extend D.melanogaster longevity pathways.