Targeting PPARγ -Synthesis And Biological Activity Evaluation Of Glycyrrhetinic Acid Derivatives

Cancer deaths are increasing dramatically,with more than 90%of cancer patients dying from tumor cell migration.More importantly,current anticancer drugs cannot significantly treat diseases well because of cell migration,caused by apoptosis resistance and multidrug resistance（MDR）of metastatic tumor cells.Studies have shown that regulation of proteins such as peroxisome proliferator-activated receptors（PPARs）could play a major role in cancer cell biology and is not associated with MDR and/or apoptosis-associated resistance phenotypes.Therefore,glycyrrhetinic acid derivatives,as a class of PPARγ-targeting compounds,can play an important role in inhibiting tumor cell migration,and have far-reaching application prospects.In this manuscript,a series of novel small-molecule agonists targeting PPARγwere designed and synthesized with18β-glycyrrhetinic acid as the basic skeleton,based on computer-aided drug design.Meanwhile,the structural characterization,anti-tumor cell proliferation activity detection,PPARγand related protein detection and the inhibition of cell migration were performed as well.In this manuscript,with the help of computer-aided drug design methods,we have found that the affinity of the drug to the receptor could be strongly increased when phenylpiperazine and methyl ester were introduced in C-3 and C-30 of 18β-glycyrrhetinic acid,respectively.Besides,molecular docking results showed that most of the compounds exhibited stronger binding ability than positive control rosiglitazone,and the compounds 4p and 4q had the highest binding ability to PPARγ（PDB Code:2HFP）,and a plurality of amino acids in the active pocket generate hydrogen bonds to increase the binding ability.Therefore,a series of Glycyrrhetinic acid derivatives（4a-4t）containing piperazine（C-3）and methyl ester（C-30）were synthesized according to three steps of chemical reaction.All of the compounds were characterized by NMR and X-ray single crystal diffraction.According to anti-tumor cell proliferation activity and cytotoxicity assay,it was found that most of the target compounds showed stronger inhibitory activity against MCF-7（human breast cancer cells）than Hep G2（human liver cancer cells）,in which compounds 4c,4p,and 4q showed better and significantly stronger inhibitory activity than the positive control rosiglitazone(4c:IC₅₀=6.898μM,4p:IC₅₀=8.073μM,4q:IC₅₀=9.500μM,rosiglitazone:IC₅₀=38.747μM)in MCF-7 cell lines.Combined with the toxicity test data of L929 cells（mouse fibroblasts）,4c and 4q compounds(4c:CC₅₀=333.885μM,4q:CC₅₀=663.226μM)were finally screened as high-efficiency and low-toxic lead compounds.Further studies have shown that the target compound can bind to PPARγand agonize it to regulate the downstream cell migration-associated protein MMP2/9,producing the ability to significantly inhibit tumor cell migration.Finally,the cell content of the apoptosis marker protein Cleaved-PARP protein increased after target compound treatment,indicating that the target compound can exert anticancer activity by promoting tumor cell apoptosis.