New PKS/NRPS Tenuazamines A-H from the Endophytic Fungus Alternaria alternata FL7 Isolated from Huperzia serrata

In this paper, we present a novel class of hybrid polyketides, tenuazamines A-H (1-8), which exhibit a unique tautomeric equilibrium from Alternaria alternata FL7. The elucidation of the structures was achieved through a diverse combination of NMR, HR-ESIMS, and ECD methods, with a focus on extensive spectroscopic data analysis. Notably, compounds 1, 4, 8-9 exhibited potent toxic effects on the growth of Arabidopsis thaliana. This research expands the structural diversity of tenuazonic acid compounds derived from endophytic fungi and provides potential hit compounds for the development of herbicides.