From extracts of the plant associated fungus Chaetosphaeronema achilleae collected in Iran, a previously unreported isoindolinone named chaetosisoindolinone (1) and a previously undescribed indanone named chaetosindanone (2) were isolated in addition to five known metabolites, 2-(2-acetyl-3,5-dihydroxyphenyl) acetic acid (3), vulculic acid (4), 2-(2-acetyl-3-hydroxy-5-methoxyphenyl)acetic acid (5), curvulin (6), and curvulol (7). Their structures were elucidated on the basis of extensive spectroscopic analysis and high-resolution mass spectrometry. The isolated compounds were tested for their antimicrobial, anti-biofilm, and nematicidal activities. Compound 2 exhibited cytotoxicity against the human breast adenocarcinoma MCF-7 cells with an IC50 value of 1.5 μg/mL. Furthermore, compounds 4 and 7 almost completely inhibited biofilm formation in Staphylococcus aureus at 256 μg/mL. Weak antimicrobial activities were also observed for some of the isolated compounds against Mucor hiemalis, Rhodoturula glutinis, Chromobacterium violaceum, and Staphylococcus aureus.
Keywords: Antibiotics; Fungi; Polyketides; Secondary metabolites.
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