Antimicrobial Compounds from the Australian Desert Plant Eremophila neglecta

• DOI: 10.1021/np070180r
• Publication Date: 2007-09-11T05:00:39Z
• Authors: Chi P. Ndi; Susan J. Semple; Hans J. Griesser; Simon M. Pyke; Mary D. Barton
• Keywords: Staphylococcus aureus; Streptococcus pyogenes; Microbial Sensitivity Tests; Medicinal; 01 natural sciences; Anti-Infective Agents; Eremophila Plant; Gram-Negative Bacteria; 580; Plants, Medicinal; Molecular Structure; Australia; Pharmacology and Pharmaceutical Sciences; Plants; Eremophila neglecta; 0104 chemical sciences; 3. Good health; Plant Leaves; Streptococcus pneumoniae; phytochemistry; Antimicrobial; compounds; Desert Climate; Diterpenes

A crude extract from the Australian desert plant Eremophila neglecta has recently been shown to possess antibacterial activity in a survey of candidate plants that may bear novel antimicrobial compounds. Bioassay-directed fractionation of the Et(2)O extract of E. neglecta using a broth microdilution assay led to the isolation of three new serrulatane-type diterpenoids, 2,19-diacetoxy-8-hydroxyserrulat-14-ene (2), 8,19-dihydroxyserrulat-14-ene (3), and 8-hydroxyserrulat-14-en-19-oic acid (4), and a known o-naphthoquinone commonly referred to as biflorin (5). The structures of 2-5 were determined using 1D and 2D NMR, FTIR, and high-resolution mass spectrometry. Compounds 3-5 showed antimicrobial activity against Gram-positive bacteria including Staphylococcus aureus, Streptococcus pyogenes, and S. pneumoniae. The minimum inhibitory concentrations (MICs) and the minimum bactericidal concentrations (MBCs) ranged from 6.5 to 101.6 microM and 12.7 to 202.9 microM, respectively. No activity was observed for these compounds against Gram-negative bacteria.