Phytochemical Composition and Insecticidal Activities of Essential oil of Thymus munbyanus (Lamiales: Lamiaceae) Aerial Parts and Its Properties Against Biomarkers of Ephestia kuehniella zeller (Lepidoptera: Pyralidae)

Abstract

This research aimed to assess the chemical composition of the essential oil (EO) of Thymus munbyanus subsp. coloratus cultivated in Annaba (Northeast Algeria) and to evaluate its potential insecticidal activity against newly molted pupae of Ephestia kuehniella Zeller (Lepidoptera: Pyralidae). The yields of EO calculated from the dry matter of the aerial part of the plant were estimated at 2.56 % (w / w). Its chemical composition has been analyzed using gas chromatography/mass spectroscopy (GC / MS). 54 Compounds were identified and the main components were carvacrol (39.11 %), paracymene (15.47 %), and thymoquinone (10.59 %). In preliminary bioassays, various doses (5, 15, 25, 40, and 100 μl / mL) of the T. munbyanus EO were tested on newly molted pupae and the inhibition doses (ID) of adult emergence were determined. In a follow-up experiment, EO of T. munbyanus applied at its ID₂₅(15.38 μl / mL) and ID₅₀(25.22 μl / mL) was evaluated on acetylcholinesterase (AChE) and glutathion S-transferases (GSTs) activities. Biomarkers measurements in the treated pupae and adults (ID₂₅ and ID₅₀) revealed an inhibition in AChE activity and activation of the detoxification system as evidenced by induction in GSTs activities. Lastly, our results proved the potential use of this material as an alternative to synthetic insecticides for controlling stored product pests.

Keywords:

• Biomarkers
• Ephestia kuehniella
• Essential oil
• GC / MS
• Thymus munbyanus