Effect Of The Crude Extracts From Six Plants On The Antibacterial And Immune Activities Of Red Swamp Crayfish

Procambarus clarkia production in China has suffered from serious disease problem caused by bacterial pathogens and this causes a significant economic losses. In order to control baeteriosis of red swamp crayfish, it is an effective way to search new antibacterial activity substance from herbal plants which are considered to be the storehouse of natural compounds. Water and ethanol extracts of Solidago canadensis L., Alternanthera philoxeroides, Zingiber officinale Rose, Allium sativum L., Sophora flavescens Ait., Cortex phellodendri were investigated for their in vitro antibacterial activity against A. hydrophila, A. sobria and V. parahaemolyticus and the immunomodulatory effect of the dietary intake of herbal extracts on the Procambarus clarkia. Result showed that:1. Sophora flavescens Ait. showed antibacterial activity against A. hydrophila, A. sobria and V. parahaemolyticus with the diameter of inhibition zones above10mm and the minimum inhibitory concentrations of5mg/ml. The activity of alkaline phosphotase and catalase in the group feeding with2%Sophora flavescens Ait. hot-water extract were significantly higher than that of control group, also the content of serum protein was significantly elevated.2. Alternanthera philoxeroides showed antibacterial activity against A. hydrophila, A. sobria and V. parahaemolyticus with the minimum inhibitory(MIC) concentrations above10mg/ml. The activity of superoxide dismutase, catalase, alkaline phosphotase, phenoloxidase, acid phosphatase in the group feeding with2%Alternanthera philoxeroides hot-water extract was significantly lower than that of control group.3. Solidago canadensis L. showed strong antibacterial activity against A. hydrophila, A. sobria and V. parahaemolyticus with the diameter of inhibition zones above15mm. The activity of alkaline phosphotase, phenoloxidase and catalase in the group feeding with 2%Solidago canadensis L. hot-water extract were significantly higher than that of control group.4. Cortex phellodendri showed strong antibacterial activity against A. hydrophila, A. sobria and V. parahaemolyticus with the diameter of inhibition zones above15mm. The hot-water extract had the MIC value of5mg/ml against A. hydrophila, and the MIC value of2.5mg/ml against A. sobria. and V. parahaemolyticu. The ethanol extract had the MIC value of5mg/ml against A. hydrophila, A. sobria. and V. parahaemolyticu. The activity of phenoloxidase and catalase in the group feeding with2%Solidago canadensis L. hot-water extract were significantly higher than that of control group.5. Of the plants selected, the most active extracts were those obtained from Allium sativum L. with the diameter of inhibition zones above20mm. The hot-water extract from Cortex phellodendri had the MIC value of5mg/ml、2.5mg/ml、2.5mg/ml against A hydrophila, A. sobria and V. parahaemolyticus. The group feeding with2%Allium sativum did not show significant difference with the control group.6. The antibacterial activity was not determined in Zingiber officinale Rosc. The activity of superoxide dismutase, catalase, phenoloxidase, acid phosphatase in the group feeding with2%Zingiber officinale Rosc, was significantly lower than that of control group.It could be concluded that Sophora flavescens Ait., Alternanthera philoxeroides, Solidago canadensis L., Cortex phellodendri, Allium sativum L. showed antibacterial activity against A. hydrophila, A. sobria and V. parahaemolyticus. The strongest antibacterial activity was determined in Allium sativum L and Alternanthera philoxeroides showed low antibacterial activity. Solidago canadensis L., Cortex phellodendri and Sophora flavescens Ait. had the positive effect on the immune factors, but the effective time was different. Administration of Alternanthera philoxeroides or Zingiber officinale Rosc. hot-water extract inhibited the immune response of red swamp crayfish.