A Novel Antibacterial Compound from Siegesbeckia glabrescens

This is the authors' abstract. We don't add key points for this paper.

The crude methanol extract of the dried aerial parts of Siegesbeckia glabrescens (Compositae) showed antibacterial activity against the foodborne pathogen Staphylococcus aureus. Bioactivity-guided separation led to the isolation of 3-(dodecanoyloxy)-2-(isobutyryloxy)-4-methylpentanoic acid from nature for the first time. The structure was determined by spectroscopic data analysis (UV, MS, and NMR). The minimal inhibitory concentration (MIC) of 3-(dodecanoyloxy)-2-(isobutyryloxy)-4-methylpentanoic acid against S. aureus was found to be 3.12 μg/mL. In addition, in a further antimicrobial activity assay against Gram-positive (B. subtilis, E. faecalis, P. acnes, S. epidermidis, S. schleiferi subsp. coagulans, S. agalactiae and S. pyrogens), and Gram-negative bacteria (E. coli and P. aeruginosa), and yeast strains (C. alibicans and F. neoformans), the antimicrobial activity of the compound was found to be specific for Gram-positive bacteria. The MIC values of the compound for Gram-positive bacteria ranged from 3.12 to 25 mg/mL. Furthermore, it was found that the 2-(isobutyryloxy)-4-methylpentanoic acid substituent may operate as a key factor in the antibacterial activity of the compound, together with the laurate group.