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Nsuala, B., Kamatou, G.P.P., Sandasi, M., Enslin, G., Viljoen, A.M. 2017. Variation in essential oil composition of Leonotis leonurus, an important medicinal plant in South Africa. Biochemical Systematics and Ecology 70: 155-161.
Leonotis leonurus has been widely used by traditional healers in southern Africa for treatment of various ailments and is well known for its reported psychoactive properties. The present study was undertaken to investigate the variation in essential oil composition between geographically distinct populations of L. leonurusin South Africa using gas chromatography. Plant material (n = 50) was collected from three provinces of South Africa. Essential oils of the aerial parts were obtained by hydrodistillation and analysed using one and two dimensional gas chromatography. Twenty-six compounds accounted for more than 80% of the total composition of the oil. Eight major constituents in the oil, representing about 50% of the total oil composition, were identified by both GCMSFID and GCxGCToFMS. These major compounds were trans-?-ocimene (0.1-5.0%),cis-?-ocimene (0.1-31.5%), ?-caryophyllene (0.3-15.0%), caryophyllene oxide (0.1-5.0%), ?-humulene (0.4-18.2%), ?-elemene (0.4-10.6%), ?-cubebene (0.2-12.0%) and germacrene D (0.1-22.1%). The study showed marked similarities in the essential oil composition between populations and revealed mostly quantitative differences using the GCMSFID method, while GCxGCToFMS data revealed both quantitative and qualitative differences in the essential oil profiles.

For the holistic assessment of chemical patterns within the data, untargeted multivariate analysis was performed using SIMCA-P+ 14.0. PCA and OPLS-DA methods identified two distinct clusters, where inland samples separated from coastal collections.