Studies On The Synthesis And Biological Activities Of Tanshinone ⅡA And Analogs

Studies on the synthesis,structural modification and biological activities of natural products play important roles in the discovery of new drugs.Tanshinones are a class of liposoluble components isolated from traditional Chinese medicine Danshen(Salvia Bunge),featuring abietane diterpene quinone scaffolds.Both natural tanshinones and their unnatural analogs have a wide range of biological activities,including cardiovascular protection,antitumor,antioxidant,anti-inflammatory,neuroprotection and other activities.In this thesis,the synthesis and biological activities of tanshinone ⅡA and unnatural tanshinone analogs were studied.First,a novel approach for the total synthesis of tanshinone ⅡA was developed in order to address the drawbacks in reported synthetic approaches of tanshinone ⅡA such as lengthy steps,harsh reaction conditions and difficulties in separation.The key steps of the new synthetic route include a base mediated furan ring formation and a late-stage acyloin condensation reaction for the construction of the o-quinone ring.Tanshinone ⅡA was obtained in 17%overall yield following a ten-step synthesis.Second,a new series of tanshinone analogs were designed based on the molecular structure of tanshinone ⅡA for the purpose of providing tanshinone analogs with improved bioavailability and anti-tumor activities.33 tanshinone analogs with various structures were prepared,which could be classified into four categories:o-quinones 3.1b～p,lactones 3.2a～f,lactams 3.3a～f and furoquinolines 3.4a～f.In vitro antitumor activities of tanshinone ⅡA and all the synthesized analogs were evaluated in 6 human tumor cell lines.SAR study revealed that ring A cleavage of tanshinone ⅡA and subsequent appending polar groups at the phenyl ring could be a promising structural optimization approach for the promotion of anti-cancer activities.Compound 3.1f was selected as an early lead with IC50S of 0.28～3.16 μM against 6 tested cell lines.Molecular docking,radioligand binding assay,tubulin polymerization assay in vitro and immunofluorescence studies in cells suggested 3.1f could bind to tubulin colchicine binding site,cause disruption of tubulin polymerization,and interfere with the normal formation of mitotic spindles.Cellular mechanistic studies revealed that 3.1f could inhibit tubule formation and induce apoptosis in A549 cells in dose-dependent manners.Tube formation assays revealed that 3.1f severely impaired the tube forming capacity of HUVECs.Scratch and Transwell assays showed that 3.1f dose-dependently suppressed the migration and invasion of HUVECs as well as A549 cells.In addition,the evaluation of in vivo activity illustrated that 3.1f obviously inhibited angiogenesis in transgenic zebrafish embryos.Third,a novel series of tanshinone-nucleoside codrug 3.5a～f was designed and synthesized in order to afford multi-target drug molecules with increased bioavailability and anti-tumor activities.In these compounds,ester linkers were used to connect tanshinone scaffolds and nucleoside drug molecules.In vitro antitumor evaluation of these codrugs in 6 human cancer cell lines led to the discovery of potent compound 3.5f with an IC50 of 0.12 μM against A549 cells.Fourth,the anti-cerebral ischemic effect of lactone analog 3.2d was studied in a mouse model of middle cerebral artery occlusion(MCAO).In mice subjected to 1 h ischemia,intraperitoneal injection of compound 3.2d at a dose of 8 mg/(kg·d)led to reduced infarct volume(8.9%)after 72 h compared with the control group(23.3%).In summary,a new method for the total synthesis of tanshinone ⅡA was developed,33 tanshinone analogs and 6 tanshinone analog-nucleoside codrug molecules were designed and synthesized,from which two anticancer drug candidates(3.1f and 3.5f)and one novel anti-cerebral ischemic molecule(3.2d)were identified.This thesis may have certain reference value for the application of natural products and their analogues in the development of new drugs.