Isolation, Identification, and Activity Evaluation of Chemical Constituents from Soil Fungus Fusarium avenaceum SF-1502 and Endophytic Fungus Fusarium proliferatum AF-04

Fusarium, a large genus of filamentous fungi, is widely distributed in soil and plants. Fusarium is a prolific source of novel chemical constituents with various bioactivities. In search for antibiotics from soil and endophytic fungi, the secondary metabolites of Fusarium avenaceum SF-1502 and Fusarium proliferatum AF-04 were investigated. An alkaloid (1), a depsipeptide (6), and five sesquiterpenoids (7-11) were isolated from the extracts of the soil fungus F. avenaceum SF-1502. Three alkaloids (2-4), a depsipeptide (5), three sesquiterpenoids (9, 11, and 12), a sesterterpene (13), and four 1,4-naphthoquinones (14-17) were also separated from the extract of the green Chinese onion derived fungus F. proliferatum AF-04. Fusaravenin (1) represents the first example of a natural naphthoisoxazole-type zwitter-ionic alkaloid, a naphthoisoxazole formic acid connected with a morpholino carbon skeleton. Cyclonerotriol B (7) is a new cyclonerane sesquiterpene. Another new sesquiterpene, 3β-hydroxy-β-acorenol (12), possesses an acorane framework. The known compounds 9 and 11 were found from both fungi. The structures of the new compounds were determined via extensive HR-ESI-MS and comparison between experimental and calculated NMR results. The biological properties of 1-5 and 7-17 were evaluated against eight anthropogenic bacteria, while 1 and 7-11 were also screened for inhibitory effects against four plant pathogen bacteria. The known compounds 8, 9, and 14-17 showed potent antibacterial activities toward some of the tested anthropogenic bacteria.