Design,Synthesis And Antitumor Activity Study Of 8-Hydroxyquinoline-Based Prodrugs

Compounds based on the 8-hydroxyquinoline（8-HQ）scaffold exert a wide range of physiological activities through the chelation of metal ions such as Cu²⁺,Fe²⁺,and Zn²⁺by phenolic hydroxy oxygen atoms and quinoline nitrogen atoms.However,uncontrolled metal chelation has the risk of significant side effects,which limits the further clinical application of these compounds.By modifying the necessary groups for the chelation of 8-HQ,the prodrug without metal chelation ability is obtained,but it can be activated and release 8-HQ and restore the metal chelation ability under specific conditions,which is an effective strategy to improve the controllability of drugs.However,existing prodrugs of 8-HQ are all modified on its hydroxyl group,resulting in limited types of 8-HQ prodrugs.In this study,the modification site of prodrug was focused on quinoline nitrogen atom,a series of new 8-HQ quaternary ammonium prodrugs were constructed,and their antitumor activity was evaluatedThe 8-HQ quaternary ammonium prodrug QUM-1～QUM-3 was constructed by alkylation of 8-HQ quinoline nitrogen,and functional groups such as pinacol phenylboronate,azide,N,N-dimethylcarbamate were introduced.The UV-visible spectrum method was used to prove that the three prodrugs could release 8-HQ through the activation of hydrogen oxide,triphenylphosphine and acetylcholinesterase,respectively,which proved the feasibility of the design of quaternary ammonium 8-HQ prodrugs,thereby enriching the strategy of 8-HQ prodrug construction.Carbohydrate prodrugs have been considered to have a wide range of applications due to their low toxicity and high targeting.In this study,the 8-HQ prodrug construction strategy was combined with sugar molecules,andβ-D-glucose was introduced to 8-HQ hydroxy-oxygen and quinoline nitrogen,respectively.Four 8-HQ hydroxy-modified glucose prodrugs（Glc-1～Glc-4）and two 8-HQ quinoline modified glucose quaternary ammonium salt prodrugs（Glc-5 and Glc-6）were synthesized.The ability of prodrugs to release 8-HQ fromβ-D-glucosidase was investigated by ultraviolet-visible spectroscopy and calcein fluorescence competition test.and it was found that all six prodrugs could respond to glycosidase and release of 8-HQ,but the release rate and release efficiency were different.The proliferative inhibitory activity of six prodrugs on two tumor cells and two normal cells was determined by MTT method,and it was found that the glycation modification improved the selectivity of the prodrug to tumor cells compared with 8-HQ,and whether glucose hydroxyl was modified by acetyl significantly affected the toxicity of the prodrug to tumor cells.It was further found that the prodrug Glc-4had the strongest toxicity to tumor cells using MTT assay(IC₅₀ of 0.69μM and 1.74μM for human ovarian cancer cells SK-OV-3 and human breast cancer cell MDA-MB-231,respectively),while Glc-2 showed the highest selectivity for tumor cells（the average selectivity index was more than 5 times higher than 8-HQ）.Next,the ability of prodrugs to induce apoptosis in tumor cells was characterized by Annexin V-FITC/PI staining,and the effect of prodrugs on tumor cell cycle distribution was investigated by cell cycle detection assays.The results again proved that Glc-4 has the strongest ability to induce apoptosis and G0/G1 phase cell cycle arrest,while Glc-2 was the most sensitive to tumor cells.In this paper,based on the application of prodrug strategy on 8-hydroxyquinoline,a novel quaternary ammonium prodrug strategy is proposed.Firstly,the universality of the application of quaternary ammonium prodrug strategy on 8-hydroxyquinoline is verified,indicating the feasibility of the design idea.Secondly,two different prodrug strategies were discussed in depth,and detailed data was provided from different dimensions,which could provide new ideas for the application of prodrug strategies on 8-hydroxyquinoline.