Study On Chemical Constituents And Their Bioactivities Of Two Strains Of Endophytic Fungi,Diaporthe Pseudomangiferae And Aspergillus Flavus,Hosted In Tylophora Ovata

Endophytic fungi,which have the potential to produce bioactive novel secondary metabolites due to their special living surrounding,are considered one of the extraordinary sources of bioactive natural products.Two strains of endophytic fungi,Diaporthe pseudomangiferae and Aspergillus flavus,were isolated from the surface sterilized leaves of Tylophora ovata,a toxic medicinal plant.In order to obtain the bioactive molecules with new structure.We conducted chemical investigations on the EtOAc extracts of D.pseudomangiferae and A.flavus,which led to the isolation of fifty compounds(1*-50,twenty-eight compounds were isolated from D.pseudomangiferae and twenty-two compounds were obtained from A.flavus).Their structures were elucidated on the basis of extensive spectroscopic analysis,including UV,IR,MS,1D NMR,2D NMR,and ECD.Among them,compounds 1*-10*and 29*-39*were new compounds;compound 1*-6*were the derivatives of dothiorelone G(Csn-B),an agonist of Nurr 7;compound 29*was a dimer of two sesquiterpenoids connected by an ester linkage;compound 30*-36*belonging to cadinene-type sesquiterpenoids possess double bond at C-3/4 and acid group at C-15.The isolated compounds were screening for their anti-fibrosis,cytotoxicity,antidiabetic antioxidative,antibacterial,and anti-inflammatory activities in vitro.The results showed that compounds 1*,4*,10*,14,16,19,and 20 inhibited TFG-β induced activation of human lung fibroblast MRC-5 cells by 17.4%,59.2%,64.0%,62.9%,41.1%,32.9%,and 52.1%at 10μM,respectively.In the MTT assay,compounds 18,19,21,and 23 displayed cytotoxicity against BGC-823 cells with IC50 values of 8.1,4.4,1.5,and 8.6μM,respectively.Compound 43 inhibited the growth of five cancer cells,including HCT-116,HepG2,BGC-823,A549,MCF7,with IC50 values of 4.66,7.37,6.42,3.76,6.91,uM,respectively.And compound 49 showed cytotoxicity to MCF7 cells with an IC50 value of 2.58μM.Moreover,compound 18 exhibited significant inhibitory activity against protein tyrosine phosphatase 1B(PTP1B)with an IC50 value of 1.44μM in the antidiabetic assay.Compounds 32-36,39,42-44,46 protected live cancer cells HepG2 from damage induced by APAP(8 mM).Finally,the biosynthesis and transformation of cadinene-type sesquiterpenoids were discussed.Compounds 29*-36*and 40-42 were suggested to be the products of the key intermediates I and II.And intermediate II might lead to the formation of 1,2(or 2,3)seco-sesquiterpenoids through Bayer-Villiger reaction.