Insecticidal and genotoxic effects of essential oils of Greek sage, Salvia fruticosa, and mint, Mentha pulegium, on Drosophila melanogaster and Bactrocera oleae (Diptera: Tephritidae)

Abstract

The essential oils (EOs) extracted from Greek sage, Salvia fruticosa, and mint, Mentha pulegium, together with their main constituents, 1,8-cineole, thujone, and camphor and pulegone and menthone, respectively, were tested for insecticidal effects on the olive fruit fly, Bactrocera oleae (Diptera: Tephritidae). The EO of Greek sage plant and its main constituents also were screened for toxic and genotoxic activities in Drosophila melano- gaster (Diptera: Tephritidae). Genotoxic activity was determined using the somatic mutation and recombination (SMART) test. Results showed that mint EO and its main constituents are the most effective insecticides against B. oleae. Among the tested constituents of Greek sage oil, 1,8-cineole was found to be the most toxic for B. oleae, whereas thujone and 1,8-cineole did not signifi- cantly differ in their toxicity against D. melanogaster. For both insects, cam- phor was found to be the weakest insecticide. Greek sage EO, 1,8-cineole and thujone showed negative genotoxic activity, whereas camphor exhibited mu- tagenic activity. Mixtures of authentic 1,8-cineole-thujone, 1,8-cineole- camphor, and pulegone-menthone, in proportions resembling those in the cor- responding oils, showed no synergistic or antagonistic interactions among the main constituents of Greek sage oil, whereas the toxicity of pulegone was suppressed in the presence of menthone, indicating antagonistic interactions. Pennyroyal oil and the compounds pulegone, menthone, 1,8-cineole, and cam- phor were significantly more effective as insecticides against the pest B. oleae than D. melanogaster.