Essential oils from five Nepeta spp. cultivated in Lithuania and toxicological evaluation of their main components

Abstract

The genus Nepeta (Lamiaceae) is widespread in central and southern Europe, Asia, the Middle East and North Africa; it has also been naturalized in North America and comprises about 300 perennial species [1]. N. cataria (catnip), which has been used for ornamental and culinary purposes and as a domestic folk-medicine remedy, is the most intensively studied among Nepeta species, [2]. Essential oils (EOs) of Nepeta spp. possess strong antimicrobial, antibacterial, antifungal, antiviral, anti-inflammatory, repellent and other activities [3,4]. The composition depends on the variety, growing site, climatic conditions, growth phase and analysis method. In general, the following main chemotypes can be distinguished: with nepetalactones, citral derivatives, 1,8-cineole and/or linalool as the dominant EO compounds [1,2]. Therefore, it was of interest to study the composition of EOs isolated from five Nepeta spp., namely N. cataria var. citriodora, N. transcaucasica, N. melissifolia, N. sibirica var. citriodora and N. nuda cultivated in Lithuania. It was determined that the yield of the hydrodistilled EO varied from 0.1 (N. nuda) to 0.6% (N. cataria var. citriodora). More than 140 volatiles were identified in the studied Nepeta spp. by GC-FID and GC´GC-TOF/MS. N. cataria var. citriodora and N. nuda may be characterized by 4aα,7α,7aα- and 4aα,7α,7aβ-nepetalactones, while N. melissifolia and N. sibirica var. citriodora contained large percentages of 1,8-cineole and caryophyllene oxide. The composition of N. transcaucasica was more complex and the oil contained citronellol, 4aα,7α,7aα- and 4aα,7α,7aβ-nepetalactones, geranial, neral, geraniol, 1,8-cineole and caryophyllene oxide as the major components. The toxicology of the main identified EO components was reviewed based on the previously reported data. In the second part of this study acetone extracts (using the solid phase obtained after hydrodistillation) and water extracts (liquid phase after hydrodistillation) from Nepeta spp. were prepared and evaluated for their antioxidant activities and total phenolics content in order to reveal the possibility of using Nepeta plants as a source of various functional food ingredients.