Volatile secondary metabolites of Micromeria dalmatica Benth. (Lamiaceae): biosynthetical and chemotaxonomical aspects

Analysis by GC and GC/MS of the essential oil obtained from above-ground parts of Micromeria dalmatica Benth. allowed the identification of 116 components, comprising 93.6% of the total oil composition. The major compounds are 3-oxygenated p-menthane monoterpenes and were identified as pulegone (29.6%), menthone (11.7%), and piperitenone (10.8%). The chemical composition of this and additional 30 oils obtained from selected Micromeria Benth. taxa were compared by using multivariate statistical analysis (agglomerative hierarchical cluster analysis and principal component analysis (PCA)). The results of statistical analyses, as well as the domination of different concurrent p-menthane-skeleton-type monoterpene biosynthetical sub-branches in the compared M. dalmatica samples, implied the occurrence of at least two different chemotypes of the mentioned species.