Objective To investigate the antifungal secondary metabolites from the rice fermentation products of the Valeriana officinalis endophytic fungus Chaetomium elatum FH-3. Methods The one strain many compounds OSMAC (OSMAC) strategy and global natural products social molecular networking (GNPS) molecular networking technology were employed for targeted separation. Chromatographic and spectroscopic methods were used for structural identification. The antifungal activity of the compounds against Colletotrichum gloeosporioides was evaluated using the mycelial growth rate method. Results A total of 12 compounds were targeted and isolated from the ethyl acetate extract of Chaetomium elatum FH-3. These compounds were identified as 4′′-methoxy-asperianas A (1), (3S,4S)-4-hydroxy-6-methoxymellein (2a), (3R,4R)-4-hydroxy-6-methoxymellein (2b), cis-4,6-dihydroxymellein (3), cis-4-hydroxymellein (4), 6-methoxymellein (5), 6,8-dihydroxy-3-methyl-3,4-dihydroisocoumarin (6), 3-methyl-6-hydroxy-8-methoxy-3,4-dihydroisocoumarin (7), xenofuranone B (8), flavipesin B (9), p-hydroxybenzaldehyde (10), and p-hydroxybenzoic acid methyl ester (11). Antifungal testing showed that compounds 1—4 exhibited significantly stronger inhibitory activity against C. gloeosporioides than the positive control carbendazim, with half-maximal effective concentration (EC₅₀) values of 15.02, 25.31, 37.89, and 47.86 μg/mL, respectively. Conclusion Compounds 1 and 2a are new butenolide and dihydroisocoumarin derivatives, named butenolide A and dihydroisocoumarin C respectively, and compounds 8 and 9 are reported for the first time from this strain. Compounds 1—9 demonstrate significant inhibitory activity against C. gloeosporioides.

Valeriana officinalis L.  /  Chaetomium elatum FH-3  /  OSMAC strategy  /  GNPS molecular networking  /  structural identification  /  antifungal