Antimicrobial Activity of Paepalanthus planifolius and its Major Components against Selected Human Pathogens

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).

Keywords:
Paepalanthus planifolius; naphthopyranone; antimicrobial activity