title: Bacterial resistance modifying agents from Lycopus europaeus.
abstract: As part of an ongoing project to identify plant natural products which modulate bacterial multidrug resistance (MDR), bioassay-guided isolation of an extract of Lycopus europaeus yielded two new isopimarane diterpenes, namely methyl-1alpha-acetoxy-7alpha 14alpha-dihydroxy-8,15-isopimaradien-18-oate (1) and methyl-1alpha,14alpha-diacetoxy-7alpha-hydroxy-8,15-isopimaradien-18-oate (2). The structures were established by spectroscopic methods. These compounds and several known diterpenes were tested for in vitro antibacterial and resistance modifying activity against strains of Staphylococcus aureus possessing the Tet(K), Msr(A), and Nor(A) multidrug resistance efflux mechanisms. At 512 microg/ml none of the compounds displayed any antibacterial activity but individually in combination with tetracycline and erythromycin, a two-fold potentiation of the activities of these antibiotics was observed against two strains of S. aureus that were highly resistant to these agents due to the presence of the multidrug efflux mechanisms Tet(K) (tetracycline resistance) and Msr(A) (macrolide resistance).
authors.affiliation: Centre for Pharmacognosy and Phytotherapy, The School of Pharmacy, University of London, 29-39 Brunswick Square, London WC1N 1AX, UK. simon.gibbons@ulsop.ac.uk
authors.forename: Simon
authors.initials: S
authors.lastname: Gibbons
authors.forename: Moyosoluwa
authors.initials: M
authors.lastname: Oluwatuyi
authors.forename: Nigel C
authors.initials: NC
authors.lastname: Veitch
authors.forename: Alexander I
authors.initials: AI
authors.lastname: Gray
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology; D004224:Diterpenes / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology*; D024901:Drug Resistance, Multiple, Bacterial; D031333:Lycopus / Q000737:chemistry*; D008826:Microbial Sensitivity Tests; D015394:Molecular Structure; D013211:Staphylococcus aureus / Q000187:drug effects* / Q000502:physiology
chemical_list: D000900:Anti-Bacterial Agents; D004224:Diterpenes; C473554:methyl-1,14-diacetoxy-7-hydroxy-8,15-isopimaradien-18-oate; C473553:methyl-1-acetoxy-7,14-dihydroxy-8,15-isopimaradien-18-oate