Design,Synthesis And Evaluation Of Indomethacin Derivatives As COX-2 Inhibitors

Nonsteroidal anti-inflammatory drugs（NSAIDs）exert their effects by inhibiting the activity of cyclooxygenase（COX）enzymes and are widely used in the treatment of inflammation.However,most of these drugs show little selectivity and tend to inhibit both COX-1 and COX-2 simultaneously.Developing new COX-2 inhibitors is of great value because the therapeutic effects of NSAIDs are mediated through the inhibition of COX-2production,while the toxic side effects are primarily the result of COX-1 inhibition.Indomethacin is a widely used classic NSAID that is commonly used as an antipyretic,anti-inflammatory,and analgesic agent for the treatment of various inflammatory diseases such as rheumatoid arthritis（RA）and osteoarthritis（OA）,among others.Similar to other classic NSAIDs,indomethacin has many adverse reactions.In this study,molecular design theory and drug activity fragment splicing principles were applied to modify the structure of indomethacin at positions 1 and 3 while maintaining its basic framework.This was achieved by introducing a cyano group,different substituted oxadiazole groups,and different substituted benzoyl groups.Four series of 62 indomethacin derivatives were designed and synthesized,and all compounds were novel compounds not reported in the literature.The structures were confirmed by ¹H-NMR,¹³C-NMR,and ESI-MS,and the structure of compound 1c,a indomethacin-3-cyano derivative,was confirmed by single crystal analysis.Starting from 2-methyl-5-methoxy-1H-indole,the indomethacin-3-cyano derivatives 1a-1n were obtained through 3-position C-H activation cyanation and 1-position acylation reactions.Using indomethacin as the starting material,the indole core-containing oxadiazole derivatives 2a-2p,3a-3p,and 4a-4p were obtained by reacting with various substituted acylhydrazines under the action of phosphorus oxychloride,followed by hydrolysis of the acylamide bond and N-acylation reactions.The COX-2 inhibitory activity of all compounds was evaluated using a COX-2 inhibitor screening kit at a concentration of 500 nmol/m L.The results showed that compounds 1a-1n and 3a-3p exhibited poor inhibitory activity,while compounds 2a-2p and 4a-4p generally showed effective inhibitory activity.Among them,compound 4a with a nitro group and compound 4f with a thiophene group exhibited good in vitro inhibitory activity,with inhibitory rates of 94.2%and 86.72%,respectively,higher than the positive control drugs indomethacin and celecoxib.Five compounds with strong inhibitory activity,namely 4a,4e,4f,2g,and 2m,were selected for preliminary evaluation of their in vivo anti-inflammatory activity using a xylene-induced mouse ear swelling acute inflammation model.Compound4f with a thiophene group also showed superior anti-inflammatory activity compared to the positive control drug indomethacin,with an ear swelling inhibition rate of 62.46%（compared to 58.66%for indomethacin at an equivalent dose）.Molecular docking results indicated that the introduction of oxadiazole groups at the C-3 position of indomethacin can enhance the compounds’affinity for COX-2,and trifluoromethyl benzoyl group played an important role in the stability of the compound-protein complex.