Chemical Composition and Insecticidal Properties ofThymus numidicus(Poiret) Essential Oil from Algeria

Abstract

Essential oils of thyme (Thymus numidicus (Poiret)) from Algeria were isolated by steam distillation, analysed by gas chromatography coupled with the mass spectrometry (GC-MS) and investigated for their insecticidal activities against Rhizopertha dominica. Contact toxicity of global oil recovered after one hour of extraction and its fraction F₁ recovered after 2.5 minutes of extraction were tested using the filter paper method. Analysis of the essential oil made it possible to identify 14 components, representing 75.4 % of the oil. The major components were thymol (51.0 %) followed by carvacrol (9.4 %), linalool (3.3 %), thymol-methyl-ether (3.2 %) and iso-caryophyllene (2.7 %). The evolution of the yield and the composition of essential oil as function of time extraction show that steam distillation is a very rapid process and the duration of extraction could be limited to 15 minutes, since more than 94 % of oil are extracted. The toxicity tests show that thyme oil and its fraction F₁ have an insecticidal activity, nevertheless, the mortality obtained for global oil are weaker compared with those obtained for the F₁ fraction. This toxicity would be allotted to the presence in strong proportion of linalool and thymol.