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 (<b>1</b>-<b>8</b>), which exhibit a unique tautomeric equilibrium from <i>Alternaria alternata</i> 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 <b>1</b>, <b>4</b>, <b>8</b>-<b>9</b> exhibited potent toxic effects on the growth of <i>Arabidopsis thaliana</i>. This research expands the structural diversity of tenuazonic acid compounds derived from endophytic fungi and provides potential hit compounds for the development of herbicides.