Study On Active Constituents From Semen Pharbitidis Agatmst Oactylogyrus Infecting Fish

Fish aquaculture in China is an important economic activity that has been growing in thelast few years. The main drawbacks for the extensive commercial production of thefreshwater fish are associated with diseases including bacterial, viral, and parasitic infections.The ecoparasites monogenean such as Dactylogyrus spp., are usually attached to the gills offreshwater fish of the family Cyprinidae and cause epithelial hyperplasia of gill lamellae.Heavy infections of the parasites occur frequently in high density environments and inducemortality in fish due to gill pathology and interference with the exchange of oxygen and ions.The most commonly used drugs for the control of monogenean parasites are praziquantel,mebendazole and trichlorfon. However, the application of these chemical-based agents hashad limited efficacy due to the raised drug-resistance caused by the frequent use andPlant-derived products have received increasing concern owing to the features such asdegradable and eco-friendly,which have stimulated the search for new control strategies.Current research efforts are increasingly focused on developing alternative drug formulations,including products from medical plants. Therefore, it is important to search for novel bulkpharmaceutical chemicals meeting the demand of health breeding in aquaculture and furtherbiomimetic synthesis, aiming to cope with the current issues including drug-resistant andaquatic products safety.Based on these points,as a natural plant, Semen pharbitidis was performed including thescreen of active extracts, bio-guided isolation and identification of the active components,spectroscopy analysis and structure elucidation etc. The results obtained in this work were asfollows:Study of active extracts of Semen pharbitidis against dactylogyrus. Five solvents withdifferent polarity including petroleum ether, chloroform, ethyl acetate, methanol, and waterwere applied for the extraction of plant samples. Anthelmintic efficacy of five differentextracts was determined in vivo and the results indicated that: methanol extract of S.pharbitidis exhibited a100%efficacy against dactylogyrus after48h when tested at700.0mgL^-1, it reached efficacy between61.5%-82.4%when tested at400-600.0mg L^-1, whichshowed that methanol extract of S. pharbitidis was the active part with potent anthelminticactivity. Bio-guided isolation and structural identification of active molecules of S. pharbitidis.Ethanol extract was successively partitioned with petroleum ether, chloroform, ethyl acetate,methanol and water, and the antiparasitic activity of parts in different solvent wereinvestigated indicating that the part in methanol showed the best antiparasitic effects.Bio-guided isolation and identification of the methanol part using various isolation techniquessuch as column chromatograph, C18chromatograph and LH-20resulted in isolation of fivecompounds (Ⅰ, Ⅱ,Ⅲ,Ⅳ, Ⅴ), the active compound Ⅱ and Ⅳ exhibited100%efficacy at11.2mg L^-1and5.5mg L^-1(48h). The structure of the active compound was elucidated byspectroscopy analysis and comparing the spectral data with the reported values, identified aspalmitic acid and pharnilatin A. The anthelmintic activities of compounds Ⅰ, Ⅲ, Ⅳ werelessthan50%when the concentration were75mg L^-1,25mg L^-1,15mg L^-1, spcifically.Compounds Ⅰ, Ⅲ, Ⅳ wereidentified as caffeic acid methyl ester, β-sitosterol,12-hydroxyabietic acid, specifically.The EC50values of palmitic acid and pharnilatin A are5.330mg L^-1(4.806-5.925) and1.410mg L^-1(1.138^-1.735) after48h.The acute toxicity of palmitic acid and pharnilatin A, were evaluated on goldfish and theresults showed that: the LC50values of palmitic acid and pharnilatin A are:13.023mg L^-1(12.443^-13.508) and7.368mg L^-1(6.763-7.931) after48h...