Design,Synthesis And Anti-inflammatory Activity Evaluation Of Isatin-based Piperazine And 1,2,4-Oxadiazole Derivatives

Inflammation is a defensive response of the body to external stimuli.Chronic inflammation has always been one of the most important diseases that people are trying to overcome.The clinically used anti-inflammatory drugs mainly include steroidal anti-inflammatory drugs and non steroidal anti-inflammatory drugs（NSAIDs）.However,these drugs generally have certain toxic and side effects,and their long-term use will lead to drug resistance.Therefore,the development of new anti-inflammatory drugs with high efficiency and low toxicity with no drug resistance is one of the key research purposes in medicinal chemistry.It is a useful strategy to develop new drugs by modifying and optimizing the structures of natural products.It is reported that isatin（2,3-indolinedione）exerts potent anti-inflammatory effect with low toxicity,so in this study,we used isatin as the lead structure to discover anti-inflammatory compounds.In addition,piperazine and 1,2,4-oxadiazole are important anti-inflammatory pharmacophores.According to the combination principles,piperazine and 1,2,4-oxadiazole were introduced into the core structure of isatin respectively.Two series of total 59 isatin derivatives were designed and synthesized,of which 58 compounds were reported for the first time.The structures of all target compounds were characterized by ¹H NMR,¹³C NMR and HR-MS.Next,the effects of these 59 target compounds on the release of NO in LPS-stimulated RAW 264.7 cells were examined.Among them,compound D3（3-（（3-（4-ethylphenyl）-1,2,4-oxadiazoles-5-yl）methyl）-1H-indene,1,2（3H）-dione）was found to be the most potent one.Furthermore,compound D3 exhibited relatively low cytotoxicity against RAW 264.7 cells at the concentration of 20μM.Based on above results,we further studied the anti-inflammatory mechanism of compound D3.First,D3 could effectively inhibit the expression of COX-2 at a dose-dependent manner.Secondly,D3 could also effectively inhibit the expression of i NOS.We then explored the influences of compound D3 in some important inflammatory signaling pathways.It was found that D3 could inhibit the phosphorylation of IκB and P65 at a concentration-dependent manner.Similarly,ERK,JNK and P38 component proteins in MAPKs were also assayed,the results indicated that compound D3 could also inhibit the phosphorylation of ERK,JNK and P38.In summary,a preliminary conclusion could be concluded that compound D3 could exert anti-inflammatory activity by inhibiting the expression of COX-2 and i NOS and blocking NF-κB and MAPK pathways.