The endophytic fungus Microsphaeropsis arundinis was isolated from the capitula of the tropical plant Paepalanthus planifolius (Eriocaulaceae). The fungus was cultivated in seven different media, and the ethyl acetate extracts were tested against tumor cell lines using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide MTT assay. The culture was scaled up using parboiled rice medium, and the crude extract was purified by classical chromatographic analyses, leading to the isolation of seven compounds. The seven compounds isolated from the culture media included a new aromatic polyketide (1) and other known metabolites. The structures of all the compounds were elucidated by 1D and 2D nuclear magnetic resonance (NMR) and high resolution mass spectrometry (HRMS) analyses. An evaluation of the cytotoxicity of all the isolated compounds showed that these compounds exhibit less activity in comparison with the extract cultured in parboiled rice.

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