Insecticide activity of peppermint and lavender extracts isolated by different methods

Increased pest resistance against traditional synthetic insecticides is the present problem of agriculture worldwide. In addition, components of these insecticides are not easily environmentally degradable and have negative effects on human health. Thus, botanical insecticides, i.e. the agents containing natural plant compounds, are expected to be applied in the future as selective, efficacious and toxicologically-safe insecticides [1,2].

Biologically active components were isolated from peppermint (Mentha piperita L.) and lavender (Lavandula angustifolia L.) using the supercritical fluid extraction (SFE). Three types of extracts were prepared using the benefit of variable solvent power of supercritical carbon dioxide under different experimental conditions, and compared in terms of chemical composition and biological activity with the products of hydrodistillation and Soxhlet extraction with ethanol and hexane. The composition of volatile oil in all extracts was determined using GC-MS and GC-FID. Insecticide activity of all isolates was determined in terms of toxicologic and antifeedant effects against model kinds of insects (Spodoptera litoralis, Musca domestica and Leptinotarsa decemlineata).

Strong insecticidal effects of all isolates were observed, but significant differences between the particular isolates and plants were found. The efficiency of CO₂ extracts was comparable with that of hydrodistillate and higher than the efficiency of other extracts. On the basis of LD₅₀ values, the peppermint isolates showed specific effect on adults of Leptinotarsa decemlineata in contrary to lavender extracts which were more effective against Musca domestica adults and Spodoptera litoralis larvae.

Acknowledgement

The authors thank the Ministry of Education, Youth and Sports (project No. 2B06049) for financial support.

References: [1] Isman, M.B. (2000) Crop. Prot. 19:603–608.

[2] Pavela, R. (2007) Pest. Technol. 1(1):47–52.