Chemical Composition and Biological Activities of Essential Oil from Plectranthus amboinicus Collected in Dak Lak, Vietnam

Plectranthus amboinicus (Lamiaceae) is a medicinal plant widely cultivated and naturalized in the tropics of the Old and New World, with a history of use in folk medicine. However, there has been no prior investigation into the chemical composition and biological properties of this species in the Dak Lak Province, Vietnam. In this study, the essential oil extracted from P. amboinicus, collected in Buon Ma Thuot City in Dak Lak Provincfe was analyzed using gas chromatography-mass spectrometry (GC-MS). A total of 89 compounds were identified, constituting 0.62% of the oil; the major constituents included 2,3,5,6-tetramethylphenol (67.94%), caryophyllene (9.74%), trans-α-bergamotene (5.82%), α-humulene (3.20%), γ-terpinene (2.5%), o-cymene (1.90%), and terpinen-4-ol (1.14%). Notably, the carvacrol content exceeded previously reported values. In addition, P. amboinicus showed strong antibacterial activity against Escherichia coli using the agar disc diffusion method, with approximately 88.35% inhibition and a diameter of 47.3 mm. The antioxidant capacity of the essential oil was evaluated with the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, yielding an antioxidant efficiency of 89.21% and an IC50 value of 44.15 μg/mL. This demonstrates the high pharmaceutical potential of the P. amboinicus species grown in Vietnam.