Studies On Toxic Components To Brine Shrimp From Endophyte Metabolites Of Toona Sinensis

Fungi are widely distributed in the world and have abundant species.In recent years,fungi and their secondary metabolites have rised an increasing number of scientists’ interest.Endophyte,especially from medicinal plants,can produce natural compounds,which have special biological activities.They provide a new way to find novel chemical structures and drugs.It plays an important role in protection of plants and pharmaceutical Industry.Toona sinensis is a deciduous tree,which belongs to Meliaceae.It has nutritious and high medicinal value.At present,the studies of Toona sinensis are limited to the metabolites of plant itself in this field,but endophytic metabolites have not been reported.Therefore,the study of Toona sinensis endophyte show a huge potential.We chose one of the endophytic fungi isolated from the root,stem,leave of Toona sinensis for the research.The chemical constituents and their bioactivities of the secondary metabolites were studied.(1)In this study,we isolated 28 strains from the root,stem,leave of Toona sinensis at first.Through the biological test of toxicity against brine shrimp,TLC detection and screening culture medium,we chose XC-16 from the leave as the best strain for fermentation and we use rice medium for fermentation condition.XC-16 was identified for Xylariales by the method of ITS sequence alignment.After fermentation,we use the methods of brine shrimp lethal and some chromatographic technology for separation.Then the structures were elucidated based on spectral data(1H-NMR,13C-NMR,MS,COSY,HSQC,HMBC).Finally,we identified the structures of three compounds:Cytochalasin E(S-1),Seco-cytochalasin E(S-2),Cytochalasin Z18(S-3).They all belong to the cytochalasins.Cytochalasin E(S-2)was a new natural product.Compound S-2 and S-3 are all open chain structures.The structure of the compound S-1 contains a 13-membered oxygen-containing ring.(2)The three natural products were tested against brine shrimp larvae.Compound S-1 was shown strong cytotoxic against brine shrimp with the value of LC50:2.79±0.14 μM/L,and the positive control TSN was 3.36 ± 0.23 μM/L.The other two compounds were shown moderate active toward brine shrimp,the value of LC50 were both over 100 μM/L.