Toxicity and biochemical efficacy of chemically characterized Rosmarinus officinalis essential oil against Sitophilus oryzae and Oryzaephilus surinamensis

The study explores the efficacy of Rosmarinus officinalis essential oil (EO) as a plant based insecticide
and its effect on acetylcholinesterase (AChE) and antioxidant enzyme system in Sitophilus oryzae and
Oryzaephilus surinamensis. GC–MS result revealed 2-methoxy-3-(2-propenyl)-phenol, 1,8-cineole, and
camphor as the major component of the EO. As a fumigant, at 0.15 ␮l/ml EO exhibited 100% toxicity
and antifeedant activity against the test insect pests without affecting seed germination. EO inhibited
acetylcholinesterase enzyme activity (>40%) in both test insect pest. A significant impairment in the
antioxidant enzyme system; superoxide dismutase (SOD), and catalase (CAT), along with the decrease in
reduced glutathione (GSH) level was observed. However, in the case of O. surinamensis GSH level showed
a biphasic response with an initial increase followed by a decline in its level. The findings revealed that
the toxicity of EO might be associated with inhibition of AChE activity and oxidative imbalance. In view
of the strong fumigant toxicity and antifeedant activity, test EO may be recommended as an eco-friendly
alternative to synthetic insecticides.