Chemical Characterization and Nematicidal Activity of the Essential Oil of Nepeta nuda L. ssp. pubescens and Nepeta curviflora Boiss. from Lebanon

The chemical characterization and the nematicidal activity of the essential oils from Nepeta nuda L. ssp. pubescens and Nepeta curviflora Boiss. growing wild in Lebanon are reported. A comparative study was carried out as, to the best of our knowledge, no information is available on Nepeta nuda L. ssp. pubescens. In addition, both Nepeta species were collected in the same geographical area in order to rule out the environmental factors influencing essential oil composition and bioactivity. The most abundant (> 5 %) components of N. nuda ssp. pubescens essential oil were pinene (12.89 %), 1-ethyl-1H-pyrrole (12.67 %), 1-cycloethyl- 1-(2-methylenecyclohexyl) ethanol (10.37 %), 3-methyl-2-cyclohexen-1-one (9.17 %) and 2,3-dimethyl-3- hexanol (5.88 %). Among oxygenated monoterpenes, two nepetalactones were identified, i.e. (E, Z)nepetalactone (2.24 %) and (Z, E)-nepetalactone (0.31 %). The major constituents (> 5 %) of N. curviflora essential oil were 2-isopropyl-5-methyl-3-cyclohexen-1-one (12.51%), (-)-spathulenol (11.73%), cis-Z-alpha-bisabolene epoxide (8.07 %), widdrol (7.0 %), (E, Z)-5,7-dodecadiene (6.93 %), dihydronepetalactone (5.57 %) and 4-propyl-cyclohexene (5.43 %). The essential oil of N. curviflora was more active than the N. nuda ssp. pubescens one against the nematode Panagrolaimus rigidus. According to the motility assay, LD50 was 0.5 mg/mL and 2.5 mg/mL 24 h after treatment with N. curviflora and N. nuda ssp. pubescens essential oil, respectively.