Variation in essential oil composition of Teucrium hircanicum L. from Iran-A rich source of (E)-α-bergamotene

In present work, the chemical composition of the essential oils obtained from dried flowering aerial parts of Teucrium hircanicum L. (Labiatae) originated from ten wild populations in Iran was analyzed by a GC-FID and GC/MS system. The oil yields varied from 0.04% to 0.1%. A total of thirty-two compounds representing 67.6-97.7% of the oil were identified. The essential oil was found to be rich in sesquiterpene hydrocarpons (E)-α-bergamotene (17.5-86.9%) and (E)-β-farnesene (0.5-21.4%). Of the total identified compounds, sesquiterpene hydrocarpons (36.1-89.7%) were included the greatest essential oil fraction in all the populations, followed by oxygenated monoterpenes (2.2-21.6%), oxygenated sesquiterpenes (0.0-14.4%) and monoterepene hydrocarbons (0.0-9.5%). Hierarchical Cluster Analysis (HCA) and Principal Component Analysis (PCA) were used to distinguish any geographical variations, indicating that the clustering of populations is related to their geographic origin. According to the GC/MS analysis, two chemotypes consisting of (E)-α-bergamotene and (E)-α-bergamotene-(E)-β-farnesene were identified in the populations.