Design,Synthesis Of Indanone-Chalcone Hybrids As Potent Human Carboxylesterase 2 Inhibitors

Human carboxylesterases(hCEs)are members of a group of serine hydrolases,which catalyze the hydrolysis of a wide variety of endogenous substences and xenobiotics bearing ester-or amide-group.Human carboxylesterase 2(hCES2A),one of the major serine hydrolases distributed in small intestine,plays a key role in the detoxification or metabolic activation of many drugs(including prodrugs),environmental poisons and carcinogens.Increasing evidence has indicated that potent hCES2A inhibitors can modulate the pharmacokinetic profiles and toxicity of some important hCES2A-substrate drugs,such as anticancer agent CPT-11.Currently,loperamide(LPA,a known anti-diarrhea agent with hCES2A inhibition activity)has been used for ameliorating the intestinal toxicity triggered by irinotecan in clinical settings.However,the moderate hCES2A inhibition potency,as well as the potential adverse effects of LPA(such as nausea,drowsiness,headache,constipation and cardiac dysrhythmia),strongly block the clinical applications of this agent.Thus,it is urgent and necessary to find more efficacious and highly specific hCES2A inhibitors as novel anti-diarrhea agents to ameliorate irinotecan-induced intestinal toxicity and intestinal dysfunction.Over the past decade,fragment-based drug design(FBDD)has been recognized as an efficient tool to design and discover promising drug candidates with desired bioactivities and drug-like properties.New drug molecules are obtained by combining or extending small molecule fragments with good activity,so as to obtain the candidate drugs with high activity.Compared with high-throughput screening(HTS)which requires large-scale compound libraries,thousands of fragment molecules can be combined into millions of drug structures in this method.In addition,the fragments with small molecular weight and high solubility have more potential to be drug-like molecules.Therefore,FBDD can be used as an effective method to design and discover potent and specific enzyme inhibitors.This topic is divided into the following parts:1.Design,synthesis and structural characterization of indanone-chalcone hybrids.In this chapter,7 indanone-chalcone hybrids were designed and synthesized by modifying the A-ring firstly.The hCES2A inhibition activities of the derivatives were routinely assayed,and compound A7 showed the strongest inhibitory activity.Then,10 indanone-chalcone hybrids were synthesized by modifying the B-ring with compound A7 as the lead compound.The yield of the series of compounds was relatively high,the purity was determined by high performance liquid chromatography(HPLC),and the structural characterization was performed by mass spectrometry and nuclear magnetic.2.Inhibitory effects of indanone-chalcone hybrids against hCES2A and structure-activity relationship investigationIn this chapter,the inhibitory effects of indanone-chalcone hybrids against hCES2A were assayed,and enzyme kinetics,molecular docking were conducted,the structure-activity relationship was discussed and summarize in the text.The results showed that the synthesized indanone-chalcone hybrids with high inhibitory activity on hCES2A,of which,compound B7 showed the strongest inhibitory activity and specificity,with the IC50 value of 0.052 and had no significant inhibition on hCES1A and butyrylcholinesterase(BuChE).Further the inhibition kinetics demonstrated that compound B7 was a potent and mixed inhibitor,with the Ki values of 0.068 μM.The inhibition of intracellular hCES2A by B7 in living HepG-2 cells was investigated and the data showed that B7 was a cell-permeable compound,which could strongly inhibit intracellular hCES2A in living cells with the IC50 values of 4.45 μM.The molecular docking simulation showed that the heterocyclic ring(ring B)of B7 created strong interactions with Leu-349,Phe-153,Ile-350,Val-353 of hCES2A,meanwhile,we also found that the hydrogen bonds could be formed between the methoxyl and the hydroxyl of ring A with Met-309 of hCES2A.The structure-activity relationship is basically consistent with the molecular docking simulation results.In summary,a series of indenone-chalcone hybrids were designed and synthesized using fragment-based drug design strategy.The results demonstrated that almost all tested indanone-chalcone hybrids display strong to moderate inhibition against hCES2A in a dose-dependent manner.Among them,compound B7 could serve as a potent and specific hCES2A inhibitor with good membrane permeability,and the structure-activity relationship also provided theoretical guidance for the further development of hCES2A inhibitors.