Chemical composition, antimicrobial, antioxidant and cytotoxic activity of the essential oil from the leaves of Stachys pilifera Benth.

Stachys pilifera Benth is an endemic species of Stachys family found in Iran with a wide application as an herbal tea. The objective of this research was to evaluate the antimicrobial, antioxidant, and cytotoxic activity of the essential oil from the aerial parts of S. pilifera. Essential oil (EO) composition analysis showed that cis-Chrysanthenyl acetate (24.9%), viridiflorol (18.3%), trans-Caryophyllene (9.8%), caryophyllene oxide (4.6%), α-terpineol (3.3%), and linalool (3.1%) were the most abundant components. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the EO showed a higher antimicrobial activity against gram-positive bacteria (Bacillus cereus and Staphylococcus aureus) than gram-negative organisms (Escherichia coli, Shigella sonnei, Pseudomonas aeruginosa, and Salmonella enterica subsp. Enterica). The antioxidant activity of EO was studied using DPPH, FRAP, and β-carotene/linoleic acid assays. IC50 for the DPPH, FRAP, and β-carotene/linoleic acid tests were 23.2, 28.7, and 16.1 µg/mL, respectively, that it was higher than the results for BHT (p ≤ 0.05). The cytotoxic activity of the EO was evaluated using HT29 and HUVEC cells and it was observed that by increasing in EO concentration from 0.026 to 19.4 ug/mL, the viability of the cells for HT29 and HUVEC reduced to 6.8 and 7.1%, respectively. The results from this study suggest the possibility to use the essential oils from Stachys pilifera Benth as a natural preservative in processed or packaged food due to its high antibacterial, antioxidant, and cytotoxic activities.