Extract Of Antibacterial Substance From Solidago Canadensis And Its Effect On The Antibacterial And Immune Activities Of Red Swamp Crayfish (Procambarus Clarkii)

Red swamp crayfish (Procambarus clarkii) farming annually suffers huge economic losses because of the problems caused by pathogenic bacteria. In recent years, red swamp crayfish farms use antibiotics to control the bacterial diseases. But extensive use of antibiotics produces bacterial resistance concomitant with antibiotic residues in animal products which can be transferred to the human body and causes toxicological effects. So, discovering new methods and natural medicines to control red swamp crayfish diseases has become one of the main research in aquaculture farming. In this study we choose S. canadensis crude extract to control common pathogens. This extract is further purified and used for further inhibition test to detect the strongest antibacterial activity against pathogens. Finally, we study its effect on the immune activity and the expression of HSP70 mRNA of red swamp crayfish This will provide the basis for the development of red swamp crayfish feed additives. Results showed that:1) Methanol, ethanol and water extracts of S. canadensis had an antibacterial activity against Aeromonas hydrophila, A. sobria and Vibrio parahaemolyticus with the diameters of inhibition zones above 9 mm. The diameters of inhibition zones of both methanol and ethanol extract were significantly higher than that of water extract. The minimum inhibitory concentrations of ethanol extract for A. hydrophila and A. sobria was 2.5mg/mL and for V. parahaemolyticus was 5mg/mL. The minimum inhibitory concentrations of methanol extract to the three kinds of bacteria were 5mg/mL and for water extract to the three kinds of bacteria was 10mg/mL. Inhibitory effect of methanol extract and ethanol extract to three kinds of bacteria were better than that of water extract.2) Among all the extracts of methanol and ethanol extract, inhibitory effect of ether and ethyl acetate extracts were better than others, and ether extract from ethanol extract was the best with the diameters of inhibition zones to A. hydrophila, A. sobria and V. Parahaemolyticus and were 45.27mm 43.69mmm、40.93mm respectively in concentration of 150mg/mL. Its inhibitory effect was better than that of 1.00% hloromycetin significantly. The minimum inhibitory concentration was 0.156mg/mL.3) The content of serum protein in the group feeding ether extract from ethanol extract was significantly higher and different concentrations ether extract could increase serum phenol oxidase activity differently. The activity of superoxide dismutase in serum and hepatopancreas in the ether extract group showed a tendency to stabilize after increase. The activity of alkaline phosphatase in serum in 0.25% nd 0.50% ther extract group and in hepatopancreas in 1.00% ther extract group were significantly higher than that of control group, and its effect was same with 1.00‰ Chloramphenicol. The activity of acid phosphatase in serum and hepatopancreas in the ether extract group is significantly higher than that of control group. The activity of catalase in hepatopancreas in the 0.50%、 1.00% ether extract group was significantly higher than that of control group, and its effect was same with 1.00‰ Chloramphenicol.4) The ether extract of S. canadensis ethanol extract can enhance the expression of HSP70 mRNA in hepatopancreas of red swamp crayfish, and the expression of HSP70 mRNA in the group feeding with 0.50% and 1.00% ether extract was significantly higher than that of control group, and the effect is same with 1.00‰ Chloramphenicol. Impact of ether extract on females and males are basically the same.It could be concluded that both alcohol extract and water extract of S. canadensis had antibacterial activity against A. hydrophila, A. sobria and V. parahaemolyticus, but antibacterial activity of alcohol extract was better than that of water extract. Of all the extracts, antibacterial activity of ether extract of ethanol extract is the best, and it is better than that of 1.00% Chloramphenicol. Different concentrations of ether extract have the positive effect on the immune factors, but the effective time is different. Different concentrations of ether extract can also enhance the expression of HSP70 mRNA in hepatopancreas, and groups feeding 0.50% and 1.00% ether extract were higher than that of other groups.