The chemical investigation of ethyl acetate extract from Paepalanthus planifolius capitula resulted in the identification of 1H-naphtho[2,3-c]pyran-1-one,9-[(6-O-β-D-glucopyranosyl-β-D-glucopyranosyl)oxy]-3,4-dihydro-10-hydroxy-7-methoxy-3-methyl, semi-vioxanthin 9-O-β-D-glucopyranoside, toralactone-9-O-β-D-glucopyranoside, paepalantine-9-O-β-D-glucopyranoside, semi-vioxanthin, 1H-naphtho[2,3-c]pyran-1-one,3,4-dihydro-9,10-dihydroxy-5,7-dimethoxy-3-methyl, vioxanthin and paepalantine dimer, and also the isolation and identification of a new naphthopyranone dimer named planifoliusin A. The chemical structures of two compounds were elucidated by performing spectroscopic 1D and 2D nuclear magnetic resonance (NMR) experiments and spectrometric HRMS (high-resolution mass spectrometry) analysis. Other six naphthopyranone dimers were proposed by MS fragmentation patterns. The minimum inhibitory concentration (MIC) values for vioxanthin (7.8 µg mL-1), planifoliusin A (15.6 µg mL-1) and the ethyl acetate extract (31.2 µg mL-1) showed antimicrobial activity against Staphylococcus aureus (ATCC 25923).

In this study, fifteen endophytic fungi were isolated from Paepalanthus planifolius (Eriocaulaceae). From the capitula, seven endophytes were screened and evaluated for their metabolomic profile and radical scavenging activity (2,2-diphenyl-1-picrylhydrazyl (DPPH) assay). Chemical investigation of ethyl acetate extract of the endophytic fungus Anthostomella brabeji resulted in the isolation of one new compound, (+)-(6R*,7S*,8R*)-6,7,8-trihydroxy-2,2-dimethyl-5,6,7,8-tetrahydro-chroman-4-one, and three known compounds: 6-hydroxy-2,2-dimethyl-5,6,7,8-tetrahydro-7,8-epoxycroman-4-one, siccayne and eutypinol. All of the compound structures were elucidated using 1D and 2D nuclear magnetic resonance (NMR) and mass spectrometry (MS) analyses. The antimicrobial activity of the compounds and A. brabeji extract were assayed against the microorganisms Staphylococcus aureus, Escherichia coli, Salmonella setubal and Candida albicans. Measured minimal inhibitory concentration (MIC) values ranged from 31.25 to 1000.0 µg mL-1.