Lippia alba (Mill.) N.E. Essential Oil Interfere with Aminoglycosides Effect Against Staphylococcus aureus Helenicy N.H. Veras 1 , Adriana R. Campos 1,2 , Fabíola F.G. Rodrigues 2 , Marco A. Botelho 1 , Henrique D.M. Coutinho 1 and José G.M. da Costa 1 * 1 Programa de Pós-Graduação em Bioprospecção Molecular, Rede Nordeste de Biotecnologia, Laboratório de Pesquisas de Produtos Naturais, Universidade Regional do Cariri, CEP 63.105-000, Bairro Pimenta, Crato, Ceará, Brazil 2 Rede Nordeste de Biotecnologia, Universidade de Fortaleza, CEP 60.811-905, Bairro Edson Queiroz, Fortaleza, Ceará, Brazil Abstract: Lippia sp. essential oils have been popularly used to treat infectious diseases and some studies have shown their effect on microorganisms control. Lippia alba (Mill.) N.E. Brown, known as “cidreira”, is a shrub easily found in Brazilian Northeast. The traditional use of their leaves, used as tea to treat some affections, justify the investment in further investigations. This work reports the L. alba essential oil chemical composition and its aminoglycosides modifying effect against Staphylococcus aureus ATCC 6538, S. aureus ATCC 25923 and S. aureus ATCC 12692. The essential oil was obtained by hydrodistillation (yield of 0.52 %) and the GC-MS analysis identified the main constituents: Geranial (31.4 %), Neral (29.5 %), β-elemene (16.5 %) and geranyl acetate (13.3 %). It was verified that the essential oil interfered with all tested aminoglycosides. The antibiotic activity of gentamicin against S. aureus ATCC 25923 was enhanced (275 %) in the presence of 12 % essential oil. The 3 % essential oil increased the effect against S. aureus ATCC 25923 (41.6 %) and S. aureus ATCC 6538 (58.3 %). Key words: Lippia alba, essential oil, chemical composition, aminoglycosides, modulatory activity. Introduction: Lippia alba (Mill.) N.E. Brown, popularly known as “erva-cidreira”, is commonly found in northeast Brazil. Among the properties attributed to this specie, the antispasmodic, antipyretic, antiinflammatory, emmenagogue, diaphoretic, analgesic and sedative actions are highlighted. These properties are related to the active constituents, as the essential oil 4,22 . In Ceará state (Brazil), the plant presents great morphological and chemical variety. Gas chromatographic analyses of the essential oils from L. alba revealed at least three chemotypes: I (myrcene and citral), II (limonene and citral) and III (limonene and carvone) 25 . The antimicrobial activity of L. alba leaves essential oil was compared in relation to the three chemotypes chemical composition. It was found that the three essential oils were active against S. aureus ATCC 6538 and Journal of Essential Oil Bearing Plants ISSN Print: 0972-060X Online: 0976-5026 www.jeobp.com *Corresponding author (José G.M. da Costa) E-mail: < galberto.martins@gmail.com > © 2011, Har Krishan Bhalla & Sons Jeobp 14 (5) 2011 pp 574 - 581 574 Received 30 November 2010; accepted in revised form 25 May 2011