Sesquiterpenoids with Phytotoxic and Antifungal Activities from a Pathogenic Fungus Aspergillus alabamensis .

Five new carotane sesquiterpenoids (asperalacids A-E ( 1 - 5 )), one new tricyclic sesquiterpenoid (4-hydroxy-5(6)-dihydroterrecyclic acid A ( 6 )), and two known analogues ( 7 - 8 ) were obtained from a seagrass-derived fungus Aspergillus alabamensis , which was speculated to be a phytopathogenic fungus, isolated from the necrotic leaves of Enhalus acoroides . The structures of 1 - 6 were established by a combination of spectroscopic methods, including comprehensive NMR analysis, mass spectrometry, conformational analysis, NMR computational methods, and ECD calculations. Compound 4 , with higher inhibitory activity on wheat ( Triticum aestivum L.) root and shoot elongation than the positive control terbutryn, a broad-spectrum systemic herbicide, is a new natural plant growth inhibitor. Compound 5 , belonging to the rare glycosylated sesquiterpenoid class, represents the first example of glycosylated carotane sesquiterpenoid whose sugar moiety was identified as α-d-glucose. Compounds 1 - 4 and 6 displayed weak to potent antimicrobial activity against the plant pathogenic fungi Fusarium oxysporum , Fusarium graminearum , and Penicillium italicum and the Gram-positive bacteria Bacillus subtilis and Staphylococcus aureus .