Chemical composition and allelopathyc activity of essential oil of Lippia sidoides Cham.

Claudia Araújo Marco1*, Erlan Teixeira1, Antonio Simplício1, Carlos Oliveira1, José Costa2, José Feitosa1

The allelopathy is a process for which products of the secondary metabolism, as terpenes phenolic, of a certain vegetal intervene significantly, generally of antagonistic form, in the development of other species of plants. The objective of this work was to chemically characterize the essential oil of Lippia sidoides Cham. growing in the Cariri cearense region, Brazil, and evaluate the allelopathyc effect of this oil on the germination of lettuce (Lactuca sativa L.), arugula (Eruca sativa Mill.), and cauliflower (Brassica oleracea L.), in pre-plantation application. The monoterpene thymol (84.90%) has been identified as the principal constituent in the essential oil. The experiment was done in randomized complete block, in 4 × 3 factorial; being used four essential oil combinations applied in three different species in pre-plantation applications. Emergence velocity index (EVI), germination percentage and mean time to germination (MTG), had been analyzed through daily counting carried out until the 14th day after sowing. Through qualitative analysis performed by gas chromatography coupled with mass spectrometry (GC/MS) were identified seven chemical constituents representing 97.82% of essential oil of L. sidoides, being that the constituent present in greater concentration in oil was the thymol (84.90%). Could be verified the occurrence of the negative allelopathyc effect of lettuce crop, because its present low EVI and greater MTG, for the other vegetable species there were no allelopathic effect.

Keywords: Allelopathy, plant oil, Lippia sidoides, Lactuca sativa, Eruca sativa, Brassica oleracea.
1Universidade Federal do Ceará UFC, Curso de Agronomia, Campus Cariri, Av. Tenente Raimundo Rocha, S/N Bairro Cidade Universitária-63.040-370, Juazeiro do Norte, Ceará, Brasil. *Corresponding author (clmarko@ufc.br).
2Universidade Regional do Cariri URCA, Programa de Pós-Graduação em Bioprospecção Molecular, Departamento de Química Biológica, Rua Cel. Antônio Luiz 1161, Pimenta, 63105-000 Crato, Ceará, Brasil.