Comparative evaluation of antioxidant and insecticidal properties of essential oils from five Moroccan aromatic herbs

This study describes the antioxidant and insecticidal activities of essential oils (EOs) of Mentha suaveolens subsp. timija, Thymus satureioides, Achillea ageratum, Cotula cinerea and Salvia officinalis widely used in Morocco as flavorings, food additives and preservatives. Sixty seven components were identified accounting for more than 95.0% of the total oils. M. suaveolens subsp. timija oil had as main components menthone and pulegone. A. ageratum oil was particularly rich in artemisyl acetate and yomogi alcohol. The essential oil of T. satureioides was characterized by high contents of carvacrol and borneol. C. cinerea oil contained trans-thujone and cis-verbenyl acetate as major constituents, whereas S. officinalis oil was characterized by trans-thujone and camphor. Antioxidant activities were examined by means of 2,2-diphenyl-1-picrylhydrazyl radical (DPPH), reducing power, β-carotene/linoleic acid bleaching and ABTS radical tests. In all assays, the highest antioxidant potency was observed in T. satureioides EO with IC50 values ranging from 0.15 ± 0.36 μg mL-1 to 0.23 ± 0.67 μg mL−1 across the four assays. The in vitro evaluation of the insecticidal activity showed that M. suaveolens subsp. timija EO present the highest insecticidal efficiency against adults of Tribolium castaneum with LD50 and LD90 values of 0.17 μL cm−2 and 0.26 μL cm−2, respectively and LT50, LT90 values ranged from 44.19 h to 2.98 h and 98.14 h to 6.02 h, respectively. Our data support the possible use of T. satureioides oil as potential antioxidant agent, while M. suaveolens subsp. timija oil can be developed as a new natural bio-insecticide.