title: Effect of 13-epi-sclareol on the bacterial respiratory chain.
abstract: 13-epi-sclareol is a labdane-type diterpene isolated from the resinous exudates of the medicinal plant species Pseudognaphalium cheiranthifolium (Lam.) Hilliard et Burtt. and P. heterotrichium (Phil.) A. Anderb. This compound has antibacterial activity only against Gram-positive bacteria, showing a bactericidal and lytic action. The interaction of 13- epi-sclareol with the bacterial respiratory chain was analyzed. The compound inhibited oxygen consumption of intact Gram-positive cells, but not with Gram-negative bacteria. The compound inhibited NADH oxidase and cytochrome c reductase activities, while coenzyme Q reductase and the cytochrome c oxidase activities were not affected. These results suggest that the target site of 13-epi-sclareol is located between coenzyme Q and cytochrome c. Using cytoplasmic membrane fractions, the results of the analysis of the enzyme activities associated with the respiratory chain complexes were the same for both Gram-positive and Gram-negative bacteria, indicating that the compound has no access to the cytoplasmic membrane of intact Gram-negative bacteria. Thus, the Gram-negative envelope may act as a physical barrier that prevents the access of this compound to the site of action.
authors.affiliation: Departamento de Biología, Facultad de Química y Biología, Universidad de Santiago de Chile, Chile.
authors.forename: Lorena
authors.initials: L
authors.lastname: Tapia
authors.forename: Janet
authors.initials: J
authors.lastname: Torres
authors.forename: Leonora
authors.initials: L
authors.lastname: Mendoza
authors.forename: Alejandro
authors.initials: A
authors.lastname: Urzúa
authors.forename: Jorge
authors.initials: J
authors.lastname: Ferreira
authors.forename: Mario
authors.initials: M
authors.lastname: Pavani
authors.forename: Marcela
authors.initials: M
authors.lastname: Wilkens
mesh_terms: D000900:Anti-Bacterial Agents / Q000008:administration & dosage / Q000494:pharmacology* / Q000627:therapeutic use; D019659:Asteraceae; D004224:Diterpenes / Q000008:administration & dosage / Q000494:pharmacology* / Q000627:therapeutic use; D004579:Electron Transport / Q000187:drug effects*; D006090:Gram-Negative Bacteria / Q000187:drug effects / Q000201:enzymology; D006094:Gram-Positive Bacteria / Q000187:drug effects / Q000201:enzymology; D006801:Humans; D008826:Microbial Sensitivity Tests; D009245:NADH Dehydrogenase / Q000096:biosynthesis; D008517:Phytotherapy; D010936:Plant Extracts / Q000008:administration & dosage / Q000494:pharmacology* / Q000627:therapeutic use
chemical_list: D000900:Anti-Bacterial Agents; D004224:Diterpenes; D010936:Plant Extracts; C070760:sclareol; D009245:NADH Dehydrogenase