Chemical constituents, quantitative analysis and insecticidal activities of plant extract and essential oil from Origanum onites L.

Origanum, widely used for food and pharmaceutical industry, belonging to the Lamiaceae family, is an aromatic and medicinal plant. The aerial parts of the Origanum onites L. were dried at shade and was extracted with methanol. Rosmarinic acid, gentisic acid, 4-hydroxybenzoic acid, protocatechuic acid, caffeic acid, vanillic acid, 4-hydroxylbenzaldehyde, p-cumaric acid, ferullic acid, apigenin-7-glucoside, and narigenin were found in O. onites methanol extract. Quantitative analyses of these compounds were determined by LC-TOF/MS and rosmarinic acid was the main constituent (32.05 mg/100 g dried plant). The essential oil was isolated by steam distillation and compounds were identified by GC-MS analysis. The essential oil included the carvacrol (88.71%) as a main product. p-Cymene (3.09%) was found as a second chief product. The essential oil exhibited excellent insecticidal activity on Sitophilus granaries and Sitophilus oryzae pests. However, methanol extract revealed the moderate activity on S. granarius pet.