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 1H, 13C, HSQC, 1H-1H 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.
Keywords: Alternaria oxytropis; Bioactivities; Desert plant; Endophytic fungus; Oxytropiols; Oxytropis glabra (Leguminosae); Swainsonine.
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