<i>Leucas zeylanica</i> (L.) W.T.Aiton and <i>leucas marrubioides</i> desf.: the essential oil chemical compositions of plants growing wild in Sri Lanka

The genus <i>Leucas</i> R.Br. (Lamiaceae) is widely distributed throughout Africa, southern Asia, and northeastern Australia. <i>Leucas zeylanica</i> (L.) W.T.Aiton and <i>Leucas marrubioides</i> Desf. are two species occurring in Sri Lanka that are extensively employed in traditional medicine. This study reports, for the first time, the chemical composition of the essential oils obtained from the wild aerial parts of these species collected in Sri Lanka. GC-MS analysis revealed that the essential oils of <i>L. zeylanica</i> (<b>Lz</b>) and <i>L. marrubioides</i> (<b>Lm</b>) are characterised by high contents of sesquiterpene hydrocarbons, with <i>β</i>-selinene (30.0%) and <i>β</i>-caryophyllene (25.6%) identified as the predominant constituents, respectively. The chemical profiles are discussed in comparison with previously published data on essential oils from other <i>Leucas</i> species. Furthermore, a comprehensive review of the volatile constituents reported to date for the genus <i>Leucas</i> is presented.