Studies On The Preparation,antioxidant Activities Of Polysaccharide From Jicama(Pachyrhizus Erosus)and Its Immune Effect On Paramisgurnus Dabryanus

Intensive,high density production mode of modern aquaculture will lead to the declining of body immune function of Paramisgurnus dabryanus,consequently,lead to diiseases occurrence and quality decreasing with P.dabryanus.The abuse of antibiotics and other drugs during the breeding process will bring great safety risks to food safety and irreversibly harm the environment.Therefore,the immune enhancer of P.dabryanus was developed to enhance its immunity and disease resistance,reduce the occurrence of disease and protect the environment.The water-soluble polysaccharide was extracted from the jicama(Pachyrhizus erosus)with ultrasonic wave.Four factors including ultrasonic treatment time,water material ratio,ultrasonic power and extraction temperature were selected as the independent variables.With response surface analysis,a quadratic regression model was established by the Box-Behnken design experiments.The results showed that optimum extraction conditions were as follows:ultrasonic treatment time 20.33 min,water material ratio 20.96:1,ultrasonic power 395.9 W and water extraction temperature67.56?.Under such conditions,the predicted and experimental values of polysaccharide yield from jicama were 8.40%and 8.28%,respectively.The scavenging effects on hydroxyl radicals,superoxide anion radicals,reductive ability,total antioxidant capacity and the inhibitory effect on lipid peroxidation of jicama polysaccharide on concentration 0.1~10 mg/m L were studied with ascorbic acid as a positive control.The results showed that scavenging effects of jicama polysaccharide on superoxide anion radicals and hydroxyl radicals were lower than the same concentration of ascorbic acid.Otherwise,the reductive ability,total antioxidant capacity(T-AOC)and the inhibitory effect of jicama polysaccharide on lipid peroxidation were close to that of the ascorbic acid.This study indicated that jicama polysaccharide had strong in vitro antioxidant activity.P.dabryanus were coelom injected at 5,10,20 and 40 g/L with jicama polysaccharide aqueous solution,with injected 0.2 mL sterile saline group as control.A series of immunology parameters were examined at 7,14,21,and 28 days after administration of polysaccharide.P.dabryanus were toxicity test of Aeromonas hydrophila at 1×10~8 colony forming units(CFU)and mortalities were recorded over a7-day period.The results demonstrated that the red cell number(RBC),the white cell number(WBC),lysozyme(LSZ),the acid phosphatase(ACP),alkaline phosphatase(ALP)and the complement C3 in serum,and the catalase(CAT),T-AOC in hepatopancreas of P.dabryanus were significant higher than those of the saline control group(P<0.05).The content of MDA in hepatopancreas of P.dabryanus were significant lower than those of the saline control group(P<0.05).Furthermore,the P.dabryanus administered with jicama polysaccharide were more resistant under the conditions of this experiment.On the whole,the P.dabryanus injected at 10 g/L weight with jicama polysaccharide had a stronger non-specific immune response and protect the immune system of P.dabryanus.