title: Antimicrobial compounds from the Australian desert plant Eremophila neglecta.
abstract: 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.
authors.affiliation: Sansom Institute, School of Pharmacy and Medical Sciences, University of South Australia, Adelaide, SA, Australia. Chi.Ndi@postgrads.unisa.edu.au
authors.forename: Chi P
authors.initials: CP
authors.lastname: Ndi
authors.forename: Susan J
authors.initials: SJ
authors.lastname: Semple
authors.forename: Hans J
authors.initials: HJ
authors.lastname: Griesser
authors.forename: Simon M
authors.initials: SM
authors.lastname: Pyke
authors.forename: Mary D
authors.initials: MD
authors.lastname: Barton
mesh_terms: D000890:Anti-Infective Agents / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology; D001315:Australia; D003889:Desert Climate; D004224:Diterpenes / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology; D041621:Eremophila Plant / Q000737:chemistry*; D006090:Gram-Negative Bacteria / Q000187:drug effects; D008826:Microbial Sensitivity Tests; D015394:Molecular Structure; D018515:Plant Leaves / Q000737:chemistry; D010946:Plants, Medicinal / Q000737:chemistry*; D013211:Staphylococcus aureus / Q000187:drug effects; D013296:Streptococcus pneumoniae / Q000187:drug effects; D013297:Streptococcus pyogenes / Q000187:drug effects
chemical_list: C524229:2,19-diacetoxy-8-hydroxyserrulat-14-ene; C524230:8,19-dihydroxyserrulat-14-ene; C524231:8-hydroxyserrulat-14-en-19-oic acid; D000890:Anti-Infective Agents; D004224:Diterpenes