Essential oil content and composition of Vitex pseudo-negundo in Iran varies with ecotype and plant organ

Medicinal plants are rich in secondary metabolites that constitute the composition of many drugs. The quantity and quality of these valuable materials are affected by climatic factors and ontogenetic growth stages. In the present study, the effects of climatic factors and different plant parts (leaf, flower and fruit) were examined on the quantity and quality of vitex essential oil (EO) (Vitex pseudo-negundo (Hausskn.) Hand.-Mzt.) in eight different regions where the plant grows. Analysis of EO samples was performed by using GC and GC–MS. Results show that the main EO compounds in vitex are α-pinene (29.5–48.9%), limonene (9.2–14.3%), α-terpinyl acetate (0.6–22%) and (E)-caryophyllene (8.1–17.7%) in different plant organs and ecotypes. The principal component analysis (PCA) was applied to develop a model of the distribution of total EO content in different plant organs based on a complex of environmental factors. The main components were the longitude, latitude, altitude, annual average precipitation and annual average temperature. These components explained about 67% of the variations. Temperature, rainfall and elevation did not show significant independent regression relationships (P ≤ 0.05) with the EO content, but had a significant correlation with some of the compounds in the EO. In different regions where the plant grows, the variations among EO contents ranged from 0.21 to 0.76% in different plant organs. The maximum and minimum EO contents were found in the leaves and fruits, respectively.