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

Origanum, widely used for food and pharmaceutical industries, belonging to the Lamiaceae family, is an aromatic and medicinal plant. The aerial parts of the Origanum onites L. were dried at shade and 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 L. 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 the isolated compounds were identified by GC-MS analysis. The essential oil included the carvacrol (88.71%) as the main product. p-Cymene (3.09%) was found as the second constituting component from frequency point of view. The essential oil exhibited excellent insecticidal activity against Sitophilus granaries and Sitophilus oryzae pests. However, methanol extract revealed a moderate activity on S. granarius pet.