title: Antibacterial serrulatane diterpenes from the Australian native plant Eremophila microtheca.
abstract: Chemical investigations of the aerial parts of the Australian plant Eremophila microtheca resulted in the isolation of three serrulatane diterpenoids, 3-acetoxy-7,8-dihydroxyserrulat-14-en-19-oic acid (1), 3,7,8-trihydroxyserrulat-14-en-19-oic acid (2) and 3,19-diacetoxy-8-hydroxyserrulat-14-ene (3) as well as the previously reported compounds verbascoside (4) and jaceosidin (5). Acetylation and methylation of the major serrulatane diterpenoid 2 afforded 3,8-diacetoxy-7-hydroxyserrulat-14-en-19-oic acid (6) and 3,7,8-trihydroxyserrulat-14-en-19-oic acid methyl ester (7), respectively. The antibacterial activity of 1-7 was assessed against a panel of Gram-positive and Gram-negative bacterial isolates. All of the serrulatane compounds exhibited moderate activity against Streptococcus pyogenes (ATCC 12344) with minimum inhibitory concentrations (MICs) ranging from 64-128 μg/mL. Serrulatane 1 demonstrated activity against all Gram-positive bacterial strains (MICs 64-128 μg/mL) except for Enterococcus faecalis and Enterococcus faecium. This is the first report of natural products from E. microtheca.
authors.affiliation: Eskitis Institute, Griffith University, Nathan, Qld 4111, Australia.
authors.forename: Emma C
authors.initials: EC
authors.lastname: Barnes
authors.forename: Angela M
authors.initials: AM
authors.lastname: Kavanagh
authors.forename: Soumya
authors.initials: S
authors.lastname: Ramu
authors.forename: Mark A
authors.initials: MA
authors.lastname: Blaskovich
authors.forename: Matthew A
authors.initials: MA
authors.lastname: Cooper
authors.forename: Rohan A
authors.initials: RA
authors.lastname: Davis
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D001315:Australia; D004224:Diterpenes / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D041621:Eremophila Plant / Q000737:chemistry*; D008826:Microbial Sensitivity Tests; D015394:Molecular Structure; D013210:Staphylococcus / Q000187:drug effects*; D013329:Structure-Activity Relationship
chemical_list: D000900:Anti-Bacterial Agents; D004224:Diterpenes
keywords: Antibacterial; Diterpenoid; Eremophila microtheca; Myoporaceae; Serrulatane