Design,Synthesis And Biological Evaluation Of Ursolic Acid Derivatives As Anti-inflammatory And Anti-tumor Agents

Cancer is a life-threatening disease and remains a major health problem around the globe.It is the second most prevalent disease after cardiovascular one.The most common method for cancer treatment is chemotherapy.Chemotherapy is becoming less effective,however,because of tumor multidrug resistance.Additionally,there is a strong relationship between cancer and inflammation.Inflammation remains a common and poorly controlled clinical problem that can be life threatening in extreme cases,including allergic reaction,autoimmune disease and organ rejection following transplantation surgery.Thus,the development of potent and effective novel anti-inflammatory and anticancer drugs is one of the most intensely pursued goals of contemporary medicinal chemists.Most solid tumors contain hypoxic regions within the tumor microenvironment and cancer cells adapted to hypoxia are highly resistant to chemotherapy and radiotherapy.Hypoxia is a hallmark of many malignant tumors and is regulated by hypoxia-inducible factor-la(HIF-la),a transcription factor orchestrating the expression of many genes that code for proteins involved in angiogenesis,glucose metabolism,cell proliferation,and metastasis.Overexpression of HIF-la in tumor cells is closely connected with increased resistance to radio-and chemotherapies,increased risk of metastasis,a more aggressive phenotype,and strengthened immune suppression.Therefore,inhibition of the HIF-la pathway may contribute to the therapies for the specific cancers,especially for those tightly correlated with hypoxia.However,the development of the chemotype of HIF-la inhibitors is still limited,and the discovery of new HIF-la inhibitors with improved efficiency is an important task for the medicinal chemists.In this paper,four series of ursolic acid derivatives containing oxadiazole,triazolone and piperazine were designed and synthesized using the splicing principle.The structures of the target compounds were characterized by 1H NMR,13C NMR and HRMS.The in vivo anti-inflammatory activity,anti-tumor activity,in vitro cytotoxicity and molecular docking simulation were carried out in this work,respectively.Anti-inflammatory results showed that most of the test compounds showed good anti-inflammatory inhibitory activity,in which ursolic acid compound 11b showed the strongest activity with inhibition rate of 69.76%,significantly better than that of the positive control drugs,which is 2-3 times more potent than indomethacin and ibuprufen.In vitro cytotoxicity of the ursolic acid derivatives showed that the test compounds did not show any significant cytotoxicity to the test tumor cells as well as the normal human cells.In addition,molecular docking study showed that ursolic acid derivatives display their anti-inflammatory effects is likely to through inhibiting the production of prostaglandins by reducing the activity of epoxidase and inhibiting the expression of key factors of inflammation to play anti-inflammatory effect.In vitro anti-tumor experiments showed that the majority of the compounds showed an excellent ability to inhibit the expression of HIF-1?.In particular,11b inhibited HIF-1? transcriptional activity under hypoxic conditions with IC50 = 36.9?M.The cytotoxicity of these compounds was also assessed by the MTT assay,and no compounds showed any appreciable cytotoxic activity(IC50>100 ?mol/L),which was lower than that of ursolic acid(ICso= 23.8 ?mol/L).The mechanism of action of the representative compound 11b was also investigated.The results of western blot and RT-PCR analysis suggested that 11b inhibits the protein synthesis of HIF-la,but not its degradation,and the 11b-mediated decrease in HIF-1? synthesis is likely because of down-regulation of HIF-1? mRNA translation.Cell proliferation analyses indicated that 11b can suppress cell proliferation and block cell cycle progression in G1 phase.Computer simulation experiments have further confirmed that the mechanism of anti-tumor action of these compounds is to exert their anti-tumor activity by inhibiting the expression of HIF-1?.Compound 11b provides a promising hit for further optimization to discover new HIF-1? inhibitors.The work might provides an experimental basis for the development of new candidates with potent anti-tumor and anti-inflammatory activities for the clinical treatment,respectively.