Compositions of Essential Oils and Some Biological Properties of Stachys laxa Boiss. & Buhse and S. byzantina K. Koch

Background and objectives: Stachys L. genus from the Lamiaceae family is distributed worldwide. It is used for medicinal purposes in traditional medicine. Stachys laxa as an endemic species and S. byzantina which grow in the north of Iran were selected in this study for analyzing the chemical compositions of the volatile oils and investigation of some biological activities. Methods: The chemical constituents of the oils from the aerial parts were analyzed by GC-MS. The antimicrobial activity of the essential oils was investigated by disc diffusion method and the MIC was determined. Toxicity and total phenolics content were surveyed by brine shrimp lethality and Folin-Ciocalteu assays, respectively. Two different methods (DPPH and FRAP) were conducted to assess the antioxidant activity of both extracts. Results: Sixty-one compounds were identified in the oils, whereas sesquiterpenes were the major components in both volatile oils. Hexadecanoic acid (16.65%) and hexahydrofarnesyl acetone (20.41%) were the main compounds in S. laxa and S. byzantina, respectively. The ethyl acetate fraction of S. byzantina showed the strongest antioxidant activity (DPPH IC50: 18.3 µg/mL; FRAP: 687.4 FeSO4.7 H2O mg /g extract) and the highest total phenolics content (115.43 gallic acid mg /g extract) compared to other fractions. The volatile oil of S. laxa showed more potent antimicrobial activity on Salmonella paratyphi A (MIC: 5.62 µg/mL). Conclusion: Both species were safe and showed no toxicity. They demonstrated strong antioxidant properties. The essential oil of S. laxa showed potent activity against Salmonella paratyphi A.