The genus Hypericum consists of the most important medicinally active plants with a wide distribution throughout the world. In the present study, 18 populations belong to three Hypericum species (H. asperulum Jaub. & Spach (HA), H. scabrum (HS) and H. vermiculare Boiss. & Hausskn. (HV)) were collected at flowering stage from different habitats. The essential oils of aerial part of plants were extracted by water distillation method and analyzed using GC-FID and GC-MS. The essential oil content of populations varied from 0.02% (in HV3) to 0.43% (in HS4). The highest essential oil content among populations of H. asperulum, H. scabrum and H. vermiculare were belonged to the HA3 (0.4%), HS4 (0.43%) and HV5 (0.38%) populations, respectively. The number, type and percentage of essential oil constituents varied among different populations. Generally, α-pinene, caryophyllene oxide, E-caryophyllene and spathulenol were the dominant components in H. asperulum and H. vermiculare populations; however α-pinene, β-pinene, limonene and E-caryophyllene were identified as the major constituents of H. scabrum populations. The major components of the essential oil (except spathulenol) were not significantly affected by habitat conditions. Cluster analysis based on the essential oil content and essential oil components divided the populations into three distinct groups. Overall, based on the essential oil content, HA3, HS4 and HV5 were identified as the superior populations. Chemical diversity in the essential oil of studied Hypericum populations provides possibility of selection of specific population for different industries.
