Effect of Collection Time on Composition of Essential Oil of Lippia gracilis Schauer (Verbenaceae) Growing in Northeast Brazil Vanessa de Carvalho Nilo Bitu 1,3 , José Galberto Martins da Costa 2 , Fabíola Fernandes G. Rogrigues 3 , Aracélio Viana Colares 3 , Henrique Douglas Melo Coutinho 4 , Marco Antônio Botelho 5 , Aline da Costa Portela 3 , Nathalia Matos de Santana 3 , Irwin R. Alencar Menezes 1 * 1 Chemistry Biology Department, Medicinal chemistry and Pharmacology Laboratory (LFQM), Regional University of Cariri, Brazil. Rua Coronel Antônio Luiz, 1161, Pimenta, CEP 63.105-000-Crato/Ceará, Brazil 2 Chemistry Biology Department, Research Laboratory of Natural Products (LPPN), Regional University of Cariri, Brazil. Rua Coronel Antônio Luiz, 1161, Pimenta, CEP 63.105-000-Crato/Ceará, Brazil 3 Leão Sampaio Facult, Av Leao Sampaio Km 3, CEP63.180-000 Juazeiro do Norte/Ceará, Brazil 4 Chemistry Biology Department, Molecular Biology and Microbiology Laboratory (LMBM), Regional University of Cariri, Brazil. Rua CoronelAntônio Luiz, 1161, Pimenta, CEP 63.105-000-Crato/Ceará, Brazil 5 Programa de Pós-graduação em Odontologia, Laboratório de Biotecnologia da Universidade Potiguar, Brazil Abstract: The specie Lippia gracilis Schauer is largely utilized for their antimicrobial properties, which are attributed to the presence of phenolic monoterpenes such as thymol and carvacrol. The aim of this study was to determine the yields and chemical composition of the essential oils obtained from fresh and dry leaves of collected at different times in the city of Crato-CE, in January 2009. The essential oils were extracted by hydrodistillation, and its components were identified by gas chromatography coupled with mass spectrophotometry. The time of plant collection should coincide with the moment of greatest expression of the active principle. Key words: Lippia gracilis, essential oils, times of collection. : Introduction The family Verbenaceae comprises approxi- mately 36 genera and 1000 species of pantropical distribution, where 17 genera and 250 species occur in Brazil, with economic potential widely exploited 1,2 . The genus Lippia, belonging to this family was first described by Linnaeus in middle of XVIII century; where the first in-depth taxonomic works were by Schauer in the following century. In Brazil, there are 111 distinct species belonging to this genus. In semi-arid northeastern Brazil, ISSN Print: 0972-060X ISSN Online: 0976-5026 *Corresponding authors (Irwin R. Alencar Menezes) E-mail: < irwinalencar@yahoo.com.br; irwin.alencar@urca.br >  2015, Har Krishan Bhalla & Sons