Antimicrobial activity of paepalanthus planifolius and its major components against selected human pathogens

Abstract

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).