Variation in the essential oils of the endangered species Cunila fasciculata Benth. (Lamiaceae)

Cunila species are popular aromatic and medical herbs commonly used in southern Brazil. The composition of the essential oils of several species of Cunila can vary greatly accordingly to the geographic distribution of the populations. Cunila fasciculata is endemic to Rio Grande do Sul State and is an endangered species. Its current distribution is limited to two sites in different physiographic regions. We analyzed air-dried samples of five populations of C. fasciculata with GC and GC coupled with a mass selective detector analysis to evaluate intra- and interpopulational variability in essential oils. We identified 20 volatile compounds in the species, and found clear quantitative and qualitative variation among the five populations. The four populations in the central region shared the same 15 components, forming a group characterized by large concentrations of the hepatotoxin menthofuran (>73%), similar to previous studies. Limonene and trans-β-caryophyllene were also found in significant amounts. In contrast, only 10 compounds were detected and identified in the essential oil extracted from the Torres population, five of which were not found in the other populations. This population represents a new chemotype for C. fasciculata in which the major compound is menthone (44.94-73.45%), followed by menthol, 4(8) p-menthene, and caryophyllene.