Sesquiterpenoids and mycotoxin swainsonine from the locoweed endophytic fungus Alternaria oxytropis

Abstract Oxytropiols A-J, ten undescribed guaiane-type sesquiterpenoids, and the mycotoxin swainsonine (SW) were isolated from the locoweed endophytic fungus Alternaria oxytropis . The chemical structures of these sesquiterpenoids were elucidated on the basis of HR-ESI-MS and NMR data including 1 H, 13 C, HSQC, 1 H- 1 H COSY, HMBC, and NOESY spectra, and the absolute configurations of these compounds were determined using a modified Mosher's method and X-ray diffraction spectroscopy. A possible biosynthetic pathway of these guaiane-type sesquiterpenoids is discussed, and proposed that post-modification oxidative enzymes might form these highly polyhydroxylated structures. Compound 1 displayed biological effects on the root growth of Arabidopsis thaliana , and SW displayed cytotoxicity against A549 and HeLa cancer cell lines.