GC-MS Analysis, Free-Radical-Scavenging and Insecticidal Activities of Essential Oil of Scrophularia oxysepala Boiss

Scrophularia oxysepala Boiss. is endemic to western and central regions of Iran, and belongs to the genus Scrophularia (family: Scrophulariaceae), which has long been used in traditional medicines. In the present work, chemical composition of the essential oil of the aerial parts of this species was analyzed. The air-dried ground aerial parts of S. oxysepala were subjected to hydro-distillation. The resulting oil was analyzed, for the first time, by the gas chromatography/mass spectrometry (GC-MS) and gas chromatography/flame ionization detection (GC-FID). Free-radical-scavenging activity of the essential oil was determined by the DPPH assay. Adults of Oryzeaphilus mercator were used for contact toxicity insecticidal assay. A total yield of 0.1 ml of essential oil per 100 g of plant dry mass was obtained, and 15 compounds were identified, representing 91.2% of total oil. The essential oil was characterized by a high content of aromatic compounds and phytol. The main constituents were phytol (25.3%), methyl benzyl alcohol (9.3%), dehydrodieugenol (6.7%), methyl benzaldehyde (5.3%) and eugenol (1.3%). The low level of free-radical-scavenging activity of the essential oil was demonstrated by the RC50 value of 1.852mg/ml, and the insecticidal activity was also found to be low. The insecticidal activity of this essential oil was not remarkable, but was time and concentration-dependent. The low free-radical-scavenging activity was probably due to its low percentage of phenolic compounds