Effects of Cirsiliol, a Flavone Isolated from Achillea fragrantissima, on rat isolated smooth muscle

Abstract

The effects of the flavone cirsiliol on rat isolated phenylephrine-precontracted proximal aorta, acetylcholine-pre-contracted trachea, urinary bladder, and uterus were studied. Cirsiliol (10⁻⁸-3×10⁻⁴M) caused concentration-dependent relaxation of the rat isolated phenylephrine-precontracted proximal aorta, acetylcholine-precontracted trachea, urinary bladder and inhibited the phasic contractions and the tone of the uterus. Cirsiliol (3×10⁻⁵, 1×10⁻⁴ and 3×10⁻⁴M) shifted to the right epinephrine concentration-effect curves on the proximal aorta and significantly inhibited the maximum contractions induced by epinephrine in this preparation. In Ca²⁺-free, depolarizing salt solution, cirsiliol (3×10⁻⁵, 1×10⁻⁴ and 3×10⁻⁴M) also shifted to the right CaCl₂ concentration-effect curves on the proximal aorta and inhibited the maximum contractions induced by 3×10⁻²M CaCl₂ whereas it had no effect on epinephrine-induced contractions in Ca²⁺-free salt solution on the same preparation. These observations suggest that the inhibitory effects of cirsiliol on smooth muscle are attributed to inhibition of transmembrane Ca²⁺ influx and not due to inhibition by cirsiliol of Ca²⁺ release from intracellular stores or of Ca²⁺-binding to Ca²⁺-binding proteins of the contractile system.

Keywords::

• Cirsiliol
• Achillea fragrantissima
• smooth muscle
• flavones
• calcium