Chemical Composition, Phytotoxic and Antimicrobial Activities of the Essential Oil ofScutellaria strigillosaHemsley

The chemical composition of the essential oil isolated by hydrodistillation from the aerial parts of Scutellaria strigillosa Hemsley was analyzed by GC-MS analysis. Forty one compounds were identified, representing 75.84% of total oil, which was found to be rich in sesquiterpene hydrocarbons (57.07%). The main constituents of the oil were: Germacrene D (37.78%), 1-octen-3-ol (8.96%), bicyclogermacrene (3.67%) and β-caryophyllene (3.02%). The phytotoxic effect of the essential oil was evaluated by conducting bioassays against a dicot plant, amaranth (Amaranthus retroflexus L.), and a monocot plant, bluegrass (Poa annua L.). Amaranth seemed to be more sensitive to the essential oil; 1 μl/ml essential oil application resulted in an 86.6% reduction on root elongation, and 3 μl/ml essential oil completely inhibited its seedling growth. In comparison, only 3 μl/ml essential oil showed significant inhibitory effect on bluegrass, which reduced shoot length to 20% of control and root length to 31% of control. The essential oil from S. strigillosa showed higher antimicrobial effects on gram positive bacteria than gram negative bacteria, and showed stronger effect on bacteria than fungi. This is the first report on the chemical composition, the phytotoxic and antimicrobial activity of the essential oil of S. strigillosa.