Design,Synthesis And Hypoxia-inducible Factor-1α Inhibitory Activity Evaluation Of Ursolic Acid And Panaxadiol Derivatives

At present,cancer still is one of the major diseases leading to human death,and its treatment methods mainly include surgery,radiotherapy,chemotherapy and targeted drugs.Hypoxia-inducible factor-1α(HIF-1α)is abundantly expressed in solid tumor cells and plays a key role in tumor cell adaptation to hypoxic environments created by rapid tumor growth.Therefore,HIF-1α has become an attractive target for the development of new anti-cancer drugs.Ursolic acid(UA)is a pentacyclic triterpenoid widely distributed in plants such as Hedyotis diffusa,Ligustrum lucidum,Ulmus mume and Prunella vulgaris in nature.It is known to possess a number of bioactive properties,such as anti-viral,anti-microbial,hepatoprotective,anti-inflammatory,and anti-cancer activities.Recently,our research group reported that UA derivative A(IC50 36.9μM)had good HIF-1α inhibitory activity without any cytotoxicity.It inhibits the protein synthesis of HIF-1α,but not its degradation,and the compound A-mediated decrease in HIF-1α synthesis is likely because of down-regulation of HIF-1α mRNA translation.Cell proliferation analyses indicated that compound A can suppress cell proliferation and block cell cycle progression in the G1 phase.Panaxadiol(PD),a natural product from Panax ginseng,Panax notoginseng and other araliaceae plants,has a wide range of pharmacological effects such as anti-hepatitis B,anti-arrhythmia,antioxidant,cardioprotective and anticancer activities.Previous research by our group found that PD had good HIF-1α inhibitory activity with a little cytotoxicity.It inhibits the protein synthesis and degradation of HIF-1α.In this study,eight series of 31 U A derivatives containing tetrazolium moiety and four series of 30 PD derivatives were designed and synthesized,all of which are new compounds according to SciFinder index.Eight series of UA derivatives are mainly modified around the C-3 hydroxyl group and the C-28 carboxyl group.Tetrazolium moiety is substituted for the triazolone in compound A at the C-28 position,and the distance between the tetrazolium and the parent is shortened or the tetrazolium moiety are amidated with the C-28 carboxyl group of UA,and then the hydroxyl group was esterified,oxidized or hydrazone-formed at the C-3 position.Six series of PD derivatives were designed and synthesized;(1)the C-3 hydroxy proup was oxidized and condensed as corresponding hydrazone.(2)α,β-unsaturated carbonyl structure was formed at C-2 and C-3 position,and then the corresponding derivatives were formed with amino compounds at C-3 position.(3)hydroxy group at C-12 position were esterified after selective oxidation of C-3 hydroxy group.The structure of the target compounds were confirmed by 1H-NMR,13C-NMR and HRMS.In this paper,the HIF-la inhibitory activities of UA and PD derivatives were tested by reporter gene method,and the toxicity effects were studied by MTT method.The results showed that 6 compounds out of 8 in series 1 and 2 of UA exhibited inhibitory effects on HIF-1α,among which compound 14b(IC50 7.53μM)showed the most potent inhibitory activity without any cytotoxicity.Most compounds in series 3 and 4 containing a terminal free tetrazole moiety showed moderate inhibitory activities in the order of meta>para>ortho position on the benzene ring.Oxidation of the C-3 hydroxy groupof the compounds in series 3 and 4 by Jones’reagent to provide series 5 and 6 compounds,all of which showed slightly weaker potency than the ones in series 3 and 4.Amidation of C-28 carboxyl group with 5-ami no tetrazole with the change of C-3 hydroxy group,simultaneously,afforded series 7 and 8,all of which showed good inhibitory activity.But some compounds showed certain cytotoxicity,such as compound 14d IC50 0.79μM showed its cytotoxicity of IC50 18.47μM.Among the PD derivatives in series 1,2,4-dichloro substituted compound showed the strongest potency(IC50 3.7μM)without any cytotoxicity;among the compounds in series 2 and 3,the most active compound is non-toxic with the activity of IC50 40μM;among the compounds in series 4,5 and 6,the p-fluorine substituted compound of the series 6 showed the most potent activity(IC50 4.8μM)without any cytotoxicity.The structure-activity relationship was preliminarily analyzed,which laid a foundation for further design and synthesis of these derivatives.