Essential Oil Chemical Composition of Wild Populations of Italian Oregano Spice (Origanum vulgare ssp. hirtum (Link) Ietswaart): A Preliminary Evaluation of Their Use in Chemotaxonomy by Cluster Analysis. 1. Inflorescences

Twenty-four steam-distilled samples of essential oils from inflorescences from Origanum vulgare ssp. hirtum (Link) Ietswaart growing wild in Calabria, southern Italy, were analyzed by gas chromatography and gas chromatography/mass spectrometry. A total of 56 compounds were identified. The main components of the essential oil were thymol and carvacrol, while their biogenetic precursors, p -cymene and γ-terpinene, were the most aboundant monoterpenes. The relative amounts of the two main constituents were comparable to the literature data on this species. Four chemotypes were identified in Calabria on the basis of the phenolic content, i.e., thymol, carvacrol, thymol/carvacrol, and carvacrol/thymol chemotypes. The first chemotype was the most frequent. A significant variability of composition possibly correlated with the individual genotypes was observed. Keywords: Oregano; Origanum vulgare ssp. hirtum; essential oil composition; GC/MS