Synthesis And Antitumor Evaluation Of Lipid-modified Quercetin And Dendrimer

Lipid modification strategy plays an important role in the research and development of drugs and drug carriers.Drug-lipid conjugates(DLCs)are conjugates obtained by covalently modifying lipid fragments on drug molecules.DLCs demonstrated several advantages including improved pharmacokinetics property,ameliorated physicochemical property,increased oral bioavailability,thereby improved bioactivity,enhanced tumor targeting,and reduced toxicity.Lipid based drug delivery systems(LBDDSs)were developed by covalently modifying lipid fragments on drug carriers.Because of their advantages of overcoming many biological barriers and good biocompatibility,LBDDSs become an important strategy to optimize drug carriers for drug delivery and gene delivery.This thesis focuses on the application of lipid modification strategy to develop novel chemical entities and gene delivery systems.Quercetin is a natural product with many biological activities,such as antitumor,inhibition of lipid accumulation,antivirus and anti-inflammation,etc.However,the poor solubility as well as easily being oxidation of quercetin have limited its further application in clinical.In this work,miltefosine,edelfosine or cholesterol were selected as lipid moiety to conjugate with quercetin resulted in lipid-quercetin conjugates and all conjugates were further characterized by ¹H-NMR,¹³C-NMR,HRMS and HPLC.By studying the physicochemical properties of the conjugates,we found that,compared to the quercetin with poor solubility,lipid-quercetin conjugates were amphiphilic.Then the antiproliferation assay on different cancer cell lines has screened our the best candidate I-1e and I-2d.Our results further showed that the antiproliferation activity of I-1e and I-2d could be attribute to down-regulating Bcl-2 protein,promoting PARP protein cleavage,inhibiting the heat shock pathway and corresponding client protein.Studies shown quercetin could prevent and treat obesity.So next,the lipid accumulation inhibiting ability of I-1e and I-2d were evaluated,results showed that they could effectively reduce the content of lipid droplets and triglycerides in Hep G2 cells via suppressing the expression of LXR?protein and PPAR?protein.Lipid-quercetin conjugates I-1e and I-2d therefore represented the first quercetin-lipid conjugates with dual activity on tumor suppression and inhibition of lipid accumulation.Dendrimers,which emerged in the 1980s,were widely used in many fields,such as gene delivery,drug delivery,tissue engineering and imaging techniques etc,thanks to their precise molecular structures,generation-dependent structures and abundant functional terminals.Lipid-modified poly(amidoamine)(PAMAM)dendrimers can self-assemble into positively charged nanoparticles and complex with gene drugs through electrostatic interaction,thereby protecting gene drugs from being metabolized during circulation in vivo and increasing the cellular uptake of gene drugs.These features made such dendrimer-lipid conjugates appealing carriers for gene delivery.In order to develop high efficient and low toxic gene drug carriers,in this thesis,we designed and synthesized cholesterol-dendrimer conjugates bearing hydrophilic,hydrophobic or stimulation response cleavage linkers as novel lipid modified PAMAM dendrimers.The structures of the conjugates were characterized by ¹H-NMR,¹³C-NMR and HRMS.Further gene delivery studies showed that the conjugates II-1b,II-2b and II-2c could deliver Akt2si RNA into cancer cells and induce gene silencing effectively,and II-3a could transfer DNA into cells leading to the expression of the corresponding proteins.Therefore,the development of dendrimer-cholesterol conjugates enriched the structural diversity of PAMAM dendrimers.This is the first report of such conjugates used in delivery of gene drug,hence open a new avenue for construct novel drug delivery system with high efficiency and low toxicity.In conclusion,in this thesis,we developed the lipid modification strategy to modify quercetin and PAMAM dendrimers,and found that the conjugates I-1e and I-2d had dual anticancer and inhibition activity on lipid accumulation.Meanwhile,dendrimer-lipid conjugates II-1b,II-2b and II-2c could efficiently deliver si RNA and induce gene silencing,as well as II-3a could deliver DNA and express corresponding protein.This work hence had proved the potential and significance of lipid modification in drug discovery and gene delivery.