Chemical composition and phytotoxicity of the essential oil of Encelia farinosa growing in the Sonoran Desert

Abstract

The essential oils from the leaves and stems of Encelia farinosa growing wild in Tucson, Arizona were obtained by hydrodistillation and analyzed by GC-MS. A total of 89 compounds were identified leaf and stem essential oils accounting for 95.7% of the leaf oil composition and 99.8% of the stem oil composition. The major components of the leaf oil were eupatoriochromene (20.8%), limonene (14.1%), α-pinene (11.6%), bicyclogermacrene (9.8%), sabinene (9.2%) and germacrene D (7.4%), while the stem oil was dominated by α-pinene (53.5%) and bicyclogermacrene (10.7%). The essential oils were screened for seed germination inhibition and seedling growth inhibition against Lactuca sativa (lettuce) and Lolium perenne (perennial ryegrass). Although the essential oils were relatively inactive in terms of inhibiting seed germination (about 40% germination inhibition of L. sativa and about 10% inhibition of L. perenne at 4.0 mg/mL), they both significantly inhibited radicle and hypocotyl elongation at 1.0 mg/mL