Comparison of antispasmodic effects of Dracocephalum kotschyi essential oil, limonene and α-terpineol

Dracocephalum kotschyi is an essential oil containing plant found in Iran. In Iranian traditional medicine, D. kotschyi has been used as antispasmodic and analgesic but so far there is no pharmacological report about its antispasmodic activity. Therefore, the objective of this research was to study antispasmodic activity of the essential oil of D. kotschyi and two of its constituents namely limonene and α-terpineol. The essential oil was obtained from aerial parts of D. kotschyi using hydrodistillation method. The main components found in the essential oil were α-pinene (10%), neral (11%), geraniol (10%), α-citral (12%), limonene (9%) and α-terpineol (1.1%). For antispasmodic studies, a portion of rat ileum was suspended under 1 g tension in Tyrode's solution at 37 °C and gassed with O2. Effect of the D. kotschyi essential oil, limonene and α-terpineol were studied on ileum contractions induced by KCl (80 mM), acetylcholine (ACh, 500 nM) and electrical field stimulation (EFS). The essential oil, in a concentration dependent manner inhibited the response to KCl (IC50=51 ± 8.7 nl/ml), ACh (IC50=19 ± 2.7 nl/ml) and EFS (IC50=15 ± 0.5 nl/ml). Limonene and α-terpineol showed same pattern of inhibitory effect on ileum contraction. Their inhibitory effects were also concentration dependent. However, limonene was more potent than the essential oil while the α-terpineol was less potent than either limonene or the essential oil. From this experiment it was concluded that D. kotschyi essential oil has inhibitory effect on ileum contractions. Limonene contribute a major role in inhibitory effect of the essential oil while α-terpineol has weak antispasmodic activity.