Helichrysum stoechas (L.) Moench (H.stoechas) is a medicinal plant traditionally used in the Iberian Peninsula to treat different disorders such as arterial hypertension.The aim of this study was to investigate the vascular effects of a polyphenolic methanolic extract of H.stoechas, which has high antioxidant activity, and its mechanism of action.
Isometric myography studies Canine - Food - KibbleDry were performed in an organ bath with rat aortic rings with intact endothelium.The H.stoechas extract produced vasorelaxation in the aortic rings that were precontracted by phenylephrine or KCl.L-NAME and Rp-8-Br-PET-cGMPS but not indomethacin or H-89; it also reduced the relaxant response evoked by H.stoechas extract on the phenylephrine-induced contractions.
H.stoechas extract reduced the response to CaCl2 similar to verapamil and reduced the phenylephrine-induced contractions comparable with heparin.TRAM-34, apamin and glibenclamide reduced relaxation induced by the H.stoechas extract.The combination of L-NAME+TRAM-34+apamin almost completely inhibited the H.
stoechas-induced effect.In conclusion, the relaxant effect of the H.stoechas extract is partially mediated by endothelium through the traction pad activation of the NO/PKG/cGMP pathway and the opening of Ca2+-activated K+ channels.Furthermore, the decrease in the cytosolic Ca2+ by the inhibition of Ca2+ influx through the L-type Ca2+ channels and by the reduction of Ca2+ release from the sarcoplasmic reticulum via the IP3 pathway is also involved.