Composition and biological activity of essential oils from Artemisia roxburghiana Besser and Elsholtzia fruticosa Rehder cultivated in Italy

The plants Artemisia roxburghiana Besser and Elsholtzia fruticosa Rehder were evaluated as innovative crops for the production of essential oils with valuable biological activity. For both species, Clevenger distillation resulted in high essential oil contents of 1.08 and 1.79 mL·100 g−1 dry weight for A. roxburghiana and E. fruticosa, respectively. According to the results of GC/FID and GC/MS analyses, the composition of essential oil of A. roxburghiana was characterized by cis-thujone (23.05%), 1,8-cineole (21.56%), and camphor (13.82%), while E. fruticosa oil was rich in 1,8-cineole (50.06%) and γ-terpinene (14.11%). The bioactivity of the oils of the two species was evaluated in vitro against both pathogenic Gram-positive and Gram-negative bacterial strains by disc diffusion assay and determination of the minimal inhibitory concentration. They were also tested as natural insecticides by carrying out mortality and fecundity analyses against the aphid Mizus persicae. E. fruticosa oil showed higher antibacterial activity compared to A. roxburghiana, particularly against Staphylococcus aureus (MIC 2.0 and 62.5 mg·mL−1) and Escherichia coli (MIC 7.8 and 62.5 mg·mL−1). Both plant species revealed high aphicidal activity against the polyphagous pest M. Persicae according to the nymph mortality and fecundity reduction, and their efficacy was comparable to that of azadyrachtin. This study shows the prospects of the two investigated species as possible innovative crops for the production of essential oils to be employed in agro-industry.