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 <i>Origanum compactum</i> essential oils (EOs) from four geographically distinct locations. Additionally, we evaluated their antioxidant properties and potential inhibitory effects on acetylcholinesterase (AChE), tyrosinase, and α-glucosidase enzymes and their insecticidal proprieties. Notably, this research also marks the first examination of the mineral composition of <i>O. compactum</i>. 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 β-carotene bleaching assays. Regarding the insecticidal effect, all studied essential oils showed a significant toxicity against <i>C. capitata</i> adults, and the toxicity was dose and time dependent. The highest insecticidal effect was observed for <i>O. compactum</i> essential oils collected from Gouman (LC₅₀ = 2.515 µL/mL, LC₉₀ = 5.502 µL/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 α-glucosidase (79.90-87.80%), highlighting their potential as natural inhibitors of these enzymes. The essential oils of <i>O. compactum</i> contain components that could be used as a basis for synthetizing derivatives or analogs with potential medicinal applications and pest control properties.