Study On Toxoplasma Gondii Activity Of Usnea Acid Derivatives And The Anti-tumor Activity Of Panaxotriol Derivatives

Natural products have always been an alternative source of chemical substances for exploring biological systems.Due to their unique chemical diversity,they are considered to be the source of new drug development.A large number of compounds have been developed from plants,microbial metabolites and marine organisms.From1981 to 2019,about 23.5%of new drugs,33.6%of small molecule drugs and 75.6%of anti-infective drugs derived from natural products and their derivatives.It has become an effective method to discover potential drugs by structural modification with natural products as lead compounds.In this paper,100 derivatives of dibenzofuran（+）-usnic acid and tetracyclic triterpenoid 20（R）-Panaxatriol were designed and synthesized.Their structures were confirmed by ¹³C-NMR,HRNMS and ¹H-NMR,and their biological activities were also evaluated.In the first chapter,37（+）-usnic acid derivatives were designed and synthesized.The IC₅₀values of these compounds were determined in He La cells（μM）and in T.gondii-infected He La cells（μM）,and their selectivity indexes（SI）were calculated.Most of the derivatives tested in this study exhibited improved anti-T.gondii activity in vitro when compared with the parent compound usnic acid and the positive control drug spiramycin.Among these derivatives,methyl（E）-（1-（6-acetyl-7,9-dihydroxy-8,9b-dimethyl-1,3-dioxo-3,9b-dihydrodibenzo[b,d]furan-2（1H）-ylidene）ethyl）phenyla laninate（D3）exhibited the strongest activity against T.gondii（Selectivity:>2.787）,demonstrating better in vitro activity than the lead compound（+）-usnic acid（Selectivity:0.96）as well as the clinically applied positive-control drug spiramycin（Selectivity:0.72）.Inaddition,D3and（E）-6-acetyl-7,9-dihydroxy-8,9b-dimethyl-2-（1-（quinolin-6-ylamino）ethylidene）diben zo[b,d]furan-1,3（2H,9b H）-dione（F3）had better inhibitory effects on T.gondii（inhibition rate:76.0%and 64.6%）in vivo than that of spiramycin（inhibition rate:55.2%）,and significantly reduced the number of tachyzoites in the peritoneal cavity of mice（p<0.001）in vivo.Furthermore,some biochemical parameters were measured,spleen indexes were comprehensively evaluated,and the results indicated that mice treated with both compound D3 and compound F3 showed reduced hepatotoxicity and significantly enhanced antioxidative effects compared to the normal group.Overall,these results revealed that D3 and F3 are promising lead compounds for the development and identification of usnic acid derivatives against T.gondii.In Chapter 2,63 20（R）-panaxatriol derivatives with substituents at C-3 and C-6were designed and synthesized.Their anti-tumor activity against human cancer cell lines（Hep3B,He La）was evaluated in vitro.Compared with the lead compound20（R）-panaxotriol,most of the synthetic derivatives showed just right inhibition of HIF-1αtranscription activity.Among them,the derivative G19 with t-butyloxycarbonyl-glycine(IC₅₀<0.3μM)showed the most effective HIF-1αtranscriptional inhibition in Hep3B cells;its efficacy was over 100 times higher than that of 20（R）-panaxotriol(IC₅₀>30μM).In addition,derivative G19dose-dependently inhibited the expression of HIF-1αprotein in He La cells induced by hypoxia,and also inhibited the nuclear accumulation of HIF-1α.Moreover,G19inhibited He La cell proliferation and promoted apoptosis in a dose-dependent manner,also inhibiting the migration of He La cells.It is worth noting that in vivo,30 mg/kg of G19 inhibited tumor growth by 70.33%,significantly inhibited tumor growth（p<0.001）,more significant than the inhibitory effect of 20（R）-panaxotriol（p<0.01）.Therefore,derivative G19 may be a potential lead compound for the development of new HIF-1αinhibitor.In conclusion,100 derivatives were designed and synthesized through structural modification of natural products（+）-usnic acid and 20（R）-Panaxatriol,and discovered D3 and F3 with the potential of anti-Toxoplasma,as well as G19 with HIF-1αinhibitory potential.This will provide a beneficial reference for natural products in new drug research and development,and it can also provide a certain reference for the research and development of anti-Toxoplasma or anti-tumor drugs...