Vasorelaxant effects and mechanisms of action of Heracleum sphondylium L. (Apiaceae) in rat thoracic aorta

Ethnopharmacological relevance

Aerial parts of Heracleum sphondylium L. (HS) are used in traditional medicine to treat hypertension. To provide pharmacological basis for this use, we investigated the vasorelaxant effects of a dichloromethane extract of HS (HSDE) and the mechanisms involved.

Materials and methods

Activity of HSDE was evaluated on rat isolated thoracic aortic rings.

Results

HSDE induced vasorelaxation in phenylephrine (PE, 10⁻⁶ mol/L) and high KCl—(6×10⁻² mol/L) pre-contracted aortic rings that was independent on the presence of endothelium. HSDE markedly decreased extracellular Ca²⁺-induced contraction in high-KCl and PE pre-challenged rings. It also inhibited the intracellular Ca²⁺ release sensitive to PE (10⁻⁶ M). The relaxant effect of HSDE were blunted by 4-amino-pyridine (4-AP, 10⁻³ mol/L), an inhibitor of voltage-dependent K⁺ channels.

Conclusion

Our results provide the first evidence that a dichloromethane extract of Heracleum sphondylium L. exhibits vasorelaxant properties through endothelium-independent mechanisms involving the inhibition of Ca²⁺ mobilization and changes in Kv channel conductances. These data argue for its use as antihypertensive therapy in traditional medicine.