The current work describes the antispasmodic action of Artemisia macrocephala, which is achieved via blocking of the calcium channels. This explains its traditional use as an antispasmodic.The crude methanolic extract of A. macrocephala was studied for possible relaxant effect(s) on spontaneous rabbits’ jejunum preparations. Analytical-grade chemicals were used in the experimental protocols. A. macrocephala gave positive tests for flavonoids, saponins, glycosides, alkaloids, and terpenes. A. macrocephala caused relaxation of spontaneous rabbits’ jejunum preparations (n=6) at a dose of 10.0 mg/mL (EC50 = 6.95 ± 0.20 mg/mL; 95% CI: 6.2 to 7.5). Contractions induced by 80 mM potassium chloride (KCl) were also relaxed by the A. macrocephala at dose of 10.0 mg/mL. Attempting to find an explanation for the possible mode of action, we found that, A. macrocephala at concentration of 1.0 mg/mL produced rightward shift in the calcium chloride curves, with EC50 value of −1.65 ± 0.02 log [Ca++] M vs control with EC50 value of −2.44 ± 0.043 for calcium chloride curves. At a concentration of 1.0 mg/mL it could produce 52.4% of the control response at log [Ca++] M = −1.6. Similarly, verapamil at a concentration of 0.1 μM produced a rightward shift, with EC50 value of −1.74 ± 0.026 log [Ca++] M (95% CI: –1.66 to –1.82; n=6) vs control with EC50 value of −2.45 ± 0.05 log [Ca++] M (95% CI: – 2.23 to –2.91; n=6). The right shift of the EC50 values is justification for the folkloric use of A. macrocephala as an antispasmodic, suggesting that the possible mode of action is through calcium channel blockade.
Key words: Antispasmodic, Artemisia macrocephala, calcium channel blocking activity, folkloric use, verapamil.