Essential oils from the aerial parts of three populations of Nepeta crassifolia (Lamiaceae), which are Iranian endemic species and four populations of N. nuda grown in northwestern Iran were obtained by hydro-distillation and examined by gas chromatography (GC) and GC–mass spectrometry (GC/MS). Overall, 37 compounds were identified in the essential oils from different populations of N. crassifolia and N. nuda. The essential oils consisted mainly of oxygenated monoterpenes and sesquiterpene aldehydes. The major components in the oils of three populations of N. crassifolia were 4aβ, 7α, 7aβ-nepetalactone (16.46-27.45%), 4aα, 7α, 7aβ-nepetalactone (13.45-17.54%), 1,8-cineole (8.15-9.70%) and elemol (14.38-22.14%), while 7aβ-nepetalactone (61-72.21%), 4aα, 7α, 7aβ-nepetalactone (8.72- 12.63%), pulegone (7.36%) and piperitenone oxide (4.12%) were identified as the main constituents in the oils of four populations of N. nuda. The essential oils from the aerial parts of two species of Nepeta sourced in northwestern Iran were rich in oxygenated monoterpenes. In conclusion, the present study indicated the essential oil components of wild populations of both Nepeta species varied with chemotypes, environmental conditions, and geographic origin.

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