Essential oil composition and antioxidant activity of Stachys officinalis subsp. algeriensis (Lamiaceae) from a wild population in Tunisia

In continuation of our research focus on the characterization of the volatile components of the spontaneous Tunisian flora, the aim of the present work was to carry out the chemical analysis of the essential oil of wood betony, Stachys officinalis subsp. algeriensis (de Noe) Franco (Lamiaceae). The volatiles were extracted by hydro-distillation and determined by gas chromatography adopting a flame ionization detector and gas chromatography coupled to mass spectrometry technique. 35 constituents were identified representing 97.7% of the total essential oil. Wood betony oil was found to be rich in sesquiterpene hydrocarbons (41.1%) and by oxygenated sesquiterpenes (31.7%). The main metabolites were δ-cadinene (13.7%), followed by cubebol (12.4%), epi-cubebol (7.4%), and α-calacorene (6.9%). The present study—the first—on the antioxidant activity of essential oils obtained from this species collected in Tunisia, showed that the oils exhibit moderate antioxidant activity and reduce 2,2′-diphenyl-1-picrylhydrazyl (radical DPPH⋅) with an effective concentration (IC50) value of 3.9 mg/mL.