Chemical Composition, Antioxidant and Anti-Enzymatic Activities, and In Vitro Insecticidal Potential of Origanum compactum (Benth.) Essential Oils

This study aimed to investigate the variation in the chemical composition of Origanum compactum essential oils (EOs) from four geographically distinct locations. Additionally, we evaluated their antioxidant properties and potential inhibitory effects on acetylcholinesterase (AChE), tyrosinase, and alpha-glucosidase enzymes and their insecticidal proprieties. Notably, this research also marks the first examination of the mineral composition of O. compactum. The chemical composition was determined using gas chromatography-mass spectrometry (GC-MS), which identified thymol (28.72-80.39%), carvacrol (6.54-61.84%), p-cymene (0.27-8.64%), linalool (1.44-1.96%), and caryophyllene oxide (1.34-1.56%) as the major constituents. Concurrently, inductively coupled plasma atomic emission spectroscopy (ICP-AES) revealed significant levels of macro and microelements, including calcium (295.50-512.20 mg/kg), potassium (195.99-398.45 mg/kg), magnesium (59.70-98.45 mg/kg), and iron (43.55-112.60 mg/kg). The EOs demonstrated notable antiradical activities through DPPH (1,1-diphenyl-2-picrylhydrazyl), FRAP (ferric reducing antioxidant power), and beta-carotene bleaching assays. Regarding the insecticidal effect, all studied essential oils showed a significant toxicity against C. capitata adults, and the toxicity was dose and time dependent. The highest insecticidal effect was observed for O. compactum essential oils collected from Gouman (LC50 = 2.515 mu L/mL, LC90 = 5.502 mu L/mL) after 48 h of treatment. Furthermore, at a concentration of 1 mg/mL, the EOs exhibited strong inhibitory effects against AChE (84.75-94.01%), tyrosinase (84.75-94.01%), and alpha-glucosidase (79.90-87.80%), highlighting their potential as natural inhibitors of these enzymes. The essential oils of O. compactum contain components that could be used as a basis for synthetizing derivatives or analogs with potential medicinal applications and pest control properties.