Rare open-chain antifungal butenolides from an endophytic Aspergillus sp.: a GNPS molecular networking-guided isolation

Chemical investigation of the endophytic fungus Aspergillus sp. FH-1 from Valeriana officinalis L., guided by GNPS molecular networking, afforded six compounds. These included two rare open-chain butenolides, designated as terrusnolides D (1) and F (2), together with four known analogues: terrusnolide A (3), versiol (4), decumbenone A (5), and decumbenone B (6). Their structures were unequivocally determined through extensive spectroscopic methods (HRESIMS, 1D/2D NMR, and ECD). Antifungal evaluation against the phytopathogen Colletotrichum gloeosporioides demonstrated that compounds 1 and 3 exhibited significant inhibitory activity, with EC50 values of 32.77 ± 1.12 μg/mL and 42.81 ± 1.01 μg/mL, respectively, both outperforming the positive control carbendazim.