RESEARCH PAPER Insecticidal activity of Origanum majorana L. essential oil as anti-cholinergic agent Sivaprasath PRABU 1 , Dapeng JING 1 , Viswanathan CHANDRAN 2 and Preethy MATHEW 3 1 Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing City, Haidian District, P.R. China 2 Rice Research Institute and Key Lab for Major Crop Diseases, Sichuan Agricultural University, Chengdu, P.R. China 3 CPL Aromas FZE, Dubai, United Arab Emirates Correspondence Sivaprasath Prabu, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Haidian District, Beijing City-100193, China, Phone: +86 13581605837; Email: shivacatchmee@gmail.comPreethy Mathew, CPL Aromas FZE, S31202, Jebel Ali Free Zone, P. O. Box No. 17643, Dubai, United Arab Emirates, Phone: +971 557914387; Email: preethymathewbt@gmail.com Received 6 November 2019; accepted 29 May 2020. doi: 10.1111/1748-5967.12459 Note: The work was conducted at Biogenix Research Center for Molecular Biology and Applied Science, Thiruvananthapuram, Kerala, India. Currently, all authors are working in different organizations Abstract The present study was focused on exploring the presence of active compounds in Origanum majorana essential oil (OmEO), and its various knock-down effects against the rice moth, Corcyra cephalonica. GC–MS analysis detected the existence of major compounds such as monoterpenes, cis-β-terpineol and terpinen-4-ol with the total proportion of 52.16%. Fumigant toxicity against adult and larvae was calculated with an LC  50 value of 11.31 and 49.83 μL/L air, respectively. The contact toxicity against adult, pupa, larvae and eggs was observed with LC  50 value 2.54, 0.95, 2.78, and 0.49 μL/L, respectively. Furthermore, the influential repellent behavior against adults has been observed. Acetylesterase (AChE) inhibition activity of OmEO was observed against adult and larvae of C. cephalonica with an IC  50 value of 35.89 and 118.54 μL/mL, respectively. Moreover, computational docking study revealed the binding affinity of Cis-β-terpineol and terpinen-4-ol towards the active binding sites of AChE. On the other hand, Fluorescence-assisted cytometry and comet assay confirmed the cytotoxic and genotoxic effect of OmEO at various concentrations on C. cephalonica. Altogether, the results showed the knock-down effect of OmEO against C. cephalonica, and it could be a potential biocontrol measure against the stored product pest. Key words: cis-β-terpineol, Corcyra cephalonica, insecticidal activity, Origanum majorana, terpinen-4-ol Introduction The major challenge faced by farmers, agro-industries, governments and researchers is to achieve food adequacy sustainably by the year 2020 (Schillhorn van Veen 1999). According to the Food and Agriculture Organization (FAO), post-harvest grain losses caused by insect damage and other biological agents correspond to about 10–40% of the total annual production, globally. Hence, synthetic pesticides such as methyl bromide and phosphine fumigants are considered to be the most effective treatments to control stored product pests for decades (Isman et al. 1991). However, these pesticides are ozone-depleting in nature (Fields & White 2002; Mansour et al. 2012) and develop pest resistance by disrupting the biological system (Bell & Wlison 1995). Researchers are in search of alternative measures to curb insect infestation. Many members of plants from the various families, belonging to Myrtaceae, Asteraceae, Piperaceae, Meliaceae, Lamiaceae, and Annonaceae are known to possess various active phyto- compounds, which act as antifeedant, repellent activity, insecticidal activity, and growth inhibitors to many insect species (Srivastava et al. 2001). Currently, very few botanical products are used commercially as insecticides, such as rotenone from Derris sp. and pyrethrins from Chrysanthemum sp. (Isman 2006). In recent years, interest in essential oil extractions has expanded because of ecological concerns and as an alternative to chemical pesticides. Plant essential oil is a hydrophobic liquid, containing complex mixtures of volatile organic compounds found in the glandular hairs or secretory Entomological Research (2020) ••–•• © 2020 The Entomological Society of Korea and John Wiley & Sons Australia, Ltd