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.