Research Article Hepatoprotective Effect of Pretreatment with Thymus vulgaris Essential Oil in Experimental Model of Acetaminophen-Induced Injury Renata Grespan, 1 Rafael Pazinatto Aguiar, 1 Frederico Nunes Giubilei, 1 Rafael Rocco Fuso, 1 Marcio José Damião, 1 Expedito Leite Silva, 2 Jane Graton Mikcha, 3 Luzmarina Hernandes, 4 Ciomar Bersani Amado, 1 and Roberto Kenji Nakamura Cuman 1 1 Department of Pharmacology and Terapeutics, State University of Maring´ a, 87020-900 Maring´ a, PR, Brazil 2 Department of Chemistry, State University of Maring´ a, 87020-900 Maring´ a, PR, Brazil 3 Department of Clinical Analysis, State University of Maring´ a, 87020-900 Maring´ a, PR, Brazil 4 Department of Morphophysiology Sciences, State University of Maring´ a, 87020-900 Maring´ a, PR, Brazil Correspondence should be addressed to Renata Grespan; rgrespan2@uem.br and Roberto Kenji Nakamura Cuman; rkncuman@uem.br Received 9 September 2013; Accepted 23 December 2013; Published 4 February 2014 Academic Editor: Luigi Gori Copyright © 2014 Renata Grespan et al. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Acute liver damage caused by acetaminophen overdose is a signifcant clinical problem and could beneft from new therapeutic strategies. Objective. Tis study investigated the hepatoprotective efect of Tymus vulgaris essential oil (TEO), which is used popularly for various benefcial efects, such as its antiseptic, carminative, and antimicrobial efects. Te hepatoprotective activity of TEO was determined by assessing serum aspartate aminotransferase (AST), alanine aminotransferase (ALT), and alkaline phosphatase (ALP) in mice. Teir livers were then used to determine myeloperoxidase (MPO) enzyme activity and subjected to histological analysis. In vitro antioxidant activity was evaluated by assessing the free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH∙)- scavenging efects of TEO and TEO-induced lipid peroxidation. TEO reduced the levels of the serum marker enzymes AST, ALT, and ALP and MPO activity. Te histopathological analysis indicated that TEO prevented acetaminophen-induced necrosis. Te essential oil also exhibited antioxidant activity, refected by its DPPH radical-scavenging efects and in the lipid peroxidation assay. Tese results suggest that TEO has hepatoprotective efects on acetaminophen-induced hepatic damage in mice. 1. Introduction Acetaminophen (APAP) at large doses causes serious liver injury that may develop into liver failure [1]. Hepatotoxicity induced by acetaminophen occurs through a biotransforma- tion reaction that forms the reactive metabolite N-acetyl- p-benzoquinone imine (NAPQI) through the cytochrome P-450 mixed function of oxidase system. Te metabolite is normally detoxifed through a conjugation reaction with reduced glutathione (GSH). However, at large doses of acetaminophen, NAPQI levels increase, ultimately depleting GSH levels. Subsequently, sulfydryl groups of hepatic pro- teins may react with the reactive metabolite, resulting in hep- atic necrosis [2, 3]. Hepatocellular degeneration and necrosis are also associated with elevated enzyme markers, such as serum alanine aminotransferase (ALT) and aspartate amino- transferase (AST) that indicate hepatotoxicity [4]. Liver injury induced by acetaminophen in mice is a commonly used experimental model for screening substances with potential hepatoprotective activity [5]. Growing interest has been observed in the analysis of these natural entities for their potential benefts to human health. Accelerating research of plants used in folk medicine to treat liver diseases and boost liver function has been performed. In plants, essential oils are natural mixtures of terpenes, mainly monoterpenes and sesquiterpenes, which have been increasingly used in complementary therapies because essential oils are usually rich sources of phytochemical mixtures [6]. Hindawi Publishing Corporation Evidence-Based Complementary and Alternative Medicine Volume 2014, Article ID 954136, 8 pages http://dx.doi.org/10.1155/2014/954136