Composition and antioxidant and antimicrobial activity of the essential oil and extracts of Stachys inflata Benth from Iran

Composition and antioxidant and antimicrobial activities of essential oil and methanol extract polar and nonpolar subfractions of Stachys inflata were determined. GC and GC/MS analyse of the essential oil showed 45 constituents representing 95.46% of the oil, the major components linalool (28.55%), α-terpineol (9.45%), spathulenol (8.37%) and (2E)-hexenal (4.62%) constituted 50.99% of it. Essential oil and extracts were also tested for their antioxidant activities using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and β-carotene/linoleic acid assays. In the DPPH test, IC50 value for the polar subfraction was 89.50 μg/ml, indicating an antioxidant potency of about 22% of that of butylated hydroxytoluene (IC50 = 19.72 μg/ml) for this extract. In β-carotene/linoleic acid assay, the best inhibition belonged to the nonpolar subfraction (77.08%). Total phenolic content of the polar and nonpolar extract subfractions was 5.4 and 2.8% (w/w), respectively. The plant also showed a week antimicrobial activity against three strains of tested microorganisms. Linalool and α-terpineol were also tested as major components of the oil and showed no antioxidant but considerable antimicrobial activities.