Geographical and environment-related variations of essential oils in isolated populations of Thymus richardii Pers. in the Mediterranean basin

•Seventy-two compounds were identified in the essential oils of six mediterranean isolated populations of Thymus richardii grex.•The highest monoterpene concentrations were found in Bosnia and Valencia populations.•β-bisabolene (>40%) being the principal constituent in Majorca samples.•Ibiza and Sicily populations show the major level of chemical similarity.•The occurrence of the chemotypes was related to summer precipitation and to deep of soils.

Composition of essential oils of different populations of Thymus richardii grex of six localities from Bosnia-Herzegovina (Konjic, Borci), Spain (Majorca, Ibiza, Valencia) and Italy (Marettimo, Sicily) were determined by GC/FID and GC/MS. The main constituents in most of the samples were aromatic monoterpenes corresponding to non-phenolic cyclic compounds (p-cymene, γ-terpinene). The highest monoterpene concentrations were found in the Bosnian samples (70%), and the lowest in samples from the Balearic Islands (<30%; Ibiza and Majorca). Sesquiterpenes were the major component (average > 50%) in samples from Majorca with β-bisabolene (>40%) being the principal constituent. Discriminant analysis (LDA) shows the differentiation of two chemotypes: A (phenol chemotype), with p-cymene and γ-terpinene as characteristic compounds and B, with β-bisabolene and carvacrol, as major and significative compounds. The occurrence of the chemotypes was related to summer positive precipitation and to deep of soils.