Study on the quantity and quality of two Nepeta species (Nepeta cataria L. and N. bracteata Benth.) essential oil under agricultural conditions

Two species Nepeta cataria L. and Nepeta bracteata Benth. (fam. lamiaceae) are native to Iran. To study the quantity and quality of the two species essential oil in the field, the seeds of eight populations from these two species were collected from natural habitats and planted in a randomized complete block design in Alborz Research Station of Research Institute of Forests and Rangelands (Karaj, Alborz province). The flowering branches were harvested at the full flowering stage and after room temperature-drying, their essential oils were extracted by hydrodistillation, and analyzed and identified by GC and GC/MS. The essential oil yield of N. cataria populations varied between 0.02 (Karaj) and 0.50% (Arak). Twenty-three compounds were identified in the essential oil of this species, and the main compound in all populations was from nepetalactone isomers. NepetalactoneIII (4aα,7β,7aα-nepetalactone) and nepetalactoneI (4aα,7α,7aα-nepetalactone) constituted 44.4 (Karaj) to 91.6% (Arak) and 0.8 (Karaj) to 15.9% (Bafgh1) of the essential oil, respectively. NepetalactoneII (4aα,7α,7aβ-nepetalactone) was observed only in the population Bafgh2 (21.2%). The amount of 1,8-cineole in the essential oil of different N. cataria populations varied from 0.4 (Taft1) to 12.8% (Karaj). The essential oil yield of N. bractaeta populations was obtained between 0.02 (Ardakan) and 0.70% (Taft2). Twenty-seven compounds were identified in the essential oil of this species, and the main compounds were 1,8-cineole (1.0, 9.6, and 41.0% in Tabas, Ardakan, and Taft2, respectively) and geranyl acetate (0.9, 3.4, and 39.8% in Tabas, Taft2, and Ardakan, respectively). In general, the results showed that the N. cataria populations were all from the same chemotype, but N. bracteata populations were from two chemotypes (ct. geranyl acetate and ct. 1,8-cineole).