Synthesis, Anthelmintic Activity Of Osthol Analogs Against Dactylogyrus In Goldfish

Today, aquaculture is an important economic activity in the world. The diseases including bacterial and parasitic infections were the main barricades in the aquaculture, which cuase large economic losses very year. At present, the control of parasitic infections mainly used the pesticides, veterinary drugs and human medicine. Because of long-term and frequency using those drugs, the threats of anthelmintic resistance, risk of residue and food safety have occurred. And many drugs had been banned to be used in aquaculture now. Therefore, it is necessary to create the newly drugs which can be only used in aquaculture, and the use of natural products and vaccine was the prospect of drugs creation. However, the development of natural products can be usually high in cost and it is hard to be widely used in practice. Total synthesis of the natural products can be a good solution to the cost. Therefore, in the present study, we total synthesis the osthol and its analogs, evaluate their anthelmintic efficacy against Dactylogyrus and analyse the structure-activity relationships to develop potential medicines for the control of fish disease. The main results are as follows:1. The osthol was total synthesized successfully by witting reaction, Williamson etherification reaction, Claisen rearrangement reaction, esterification reaction and alkene metathetical reaction using 2, 4-dihydroxy benzaldehyde as the initial material, yielding 34.5%. All the intermediates and products were identified by IR, EI-MS, 1H-NMR and 13C-NMR. In addition, we did some researches on the recycle and re-catalysis of the catalyst in the key reaction.2. Ten analogs of osthol had been synthesized and these compounds have been identified by 1H-NMR and 13C-NMR as 7-methoxy coumarin (10), 7-(2-methyl-2- allyloxy) coumarin (11), 7-hydroxy-4-methyl coumarin (12), 7-methoxy-4-methyl coumarin (13), 7-allyloxy-4-methyl coumarin (14), 4-methyl-7-(2-methyl-2-allyloxy) coumarin (15), 7-(1,1-dimethyl-2-allyloxy)-4-methyl coumarin (16), 8-allyl-7-allyloxy coumarin (17), 8-allyl-7-(2-methyl-2-allyloxy) coumarin (18), 8-allyl-7-(1,1-dimethyl-2-allyloxy) coumarin (19).3. The total synthesis osthol were tested by in vivo anthelmintic assay against Dactylogyrus Intermedius and the results showed that the osthol exhibits 100.0% efficacy at the concentration of 2.0 mg/L and this concentration was also safe for fish.4. Among the intermediates and analogs, compound 19 showed high activity, the anthelmintic efficacy was 100% at the concentration of 3.0 mg/L and the concentration was also safe for fish. Compound 2 also exhibited 100% efficacy at 3.0 mg/L but the concentration was 50% toxicity to fish. While compound 17 was 100% efficacy at 4.0 mg/L but the concentration was also 50% toxicity to fish.5. Two new compounds, compound 17 and 18, showed different anthelmintic efficacy. Compound 17 exhibited 100% efficacy at 4.0 mg/L but the concentration was toxicity to fish. While the compound 18 was very toxicity to fish with the 100% lethal concentration of 2.0 mg/ L, but the anthelmintic efficacy was only 58.0% at this concentration.