Composition and bioactivity of essential oil from Stachys macrostachya (Wend.) Briq

Stachys species belonging to Lamiaceae family have been used for medicinal purposes since ancient times. The aim of the present study was to investigate the chemical compositions and antibacterial, anti-tyrosinase activities of the essential oil of Stachys macrostachya. The essential oil was prepared by hydrodistillation method using a Clevenger-type apparatus and chemical composition was determined by gas chromatography (GC). The antibacterial activity of essential oil was performed by the disc diffusion and microdilution broth method against five Gram-positive and two Gram-negative bacteria. The tyrosinase inhibitory activity was evaluated by minor modifications of Masuda's method. According to the results of GC analyses, twenty-three compounds were identified representing 91.9% of the total volatile composition. The main compounds were germacrene D (12.2%), globulol (10.9%), α-pinene (9.7%), and valencene (7.6%). The present study showed that the tested essential oil of S. macrostachya exhibited antibacterial activity against Acinetobacter baumannii (MIC 62.50 μg/mL) and tyrosinase inhibition activity (IC50 22.86 ± 0.82 μg/mL). These results suggest that the essential oil could be exploited as a potential source of natural antimicrobial agents of this bacterium as well as tyrosinase inhibitors.