Study On Antimycotic Activity Against Fish-pathogenic Saprolegnia Fungus Of Litsea Cubeba Extraction Oil

Litsea cubeba extraction oil(LEO), a kind of plant extracts, was of excellent antioxidative capacity and antibacterial properties. Saprolegnia was a fungal pathogen which caused some severe aquatic diseases. So the inhibition of it played a core role in the study on Saprolegnia in China. Saprolegnia monoica Pringsh was an important species,which had been found in the northeast, north, south-east coast and the inland provinces of China. Saprolegnia monoica adapted to a wide range of temperatures, almost could be seen all year round.Sexual reproduction of Saprolegnia monoica was induced and a large number of oospores was collectted.The M38 program of Clinical Laboratory Standards Institute of U.S. (CLSI) was improved and introduced into the field of aquatic diseases drug screening.12 kinds of agents'minimum inhibitory concentration (MICgo) against Saprolegnia monoica were identified using this method, in order as follow:malachite green>disulfide-cyano-methane>salicylaldehyde>thiabendazole>citral>LEO>LGA> o-phthalaldehyde>glutaraldehyde> LM> matrine>isothiazolin-one.The impact of pH on the results was greater than temperature.Saprolegnia monoica oospores were photoed by ordinary microscope and electron microscopes after had been treated 1h with LEO and LGA.Analysis that: LEO could effectively kill the hyphas with the cell wall and membrane structures, separated them,destroy all intracellular organelles with a full range of destructive power.The extent of damage to the oosproes cell wall is lighter, destroyed the nutrients so that oospore germination was inhibitted.It found that acute toxicity of drugs againt Tilapia nilotica order as follows: disulfide cyano-methane>Salicylaldehyde> LM> citral>LEO> LGA; while Anguilla Japonica:disulfide cyano-methane>salicylaldehyde>citral> LGA> LEO. T-AOC, GSH, GST and total glutathione of experimental animals were choosen as measured indicators in sub-acute toxicity test. The results showed that:at low concentrations, the change extent of T-AOC was at a low level, so that the overall anti-oxidant function of fish does not result in big damage. It was found through the GST, total glutathione and GSH detection:in Detoxication process of fish, Tilapia nilotica gills was of a certain extent of damage, gill tissue GSH redox pathway was more important than that of liver.,while Anguilla Japonica:GSH combinative metabolic pathway in gill tissue played the core role. The liver function of experimental animals hadn't suffered in a severe impact.