Magnolol blocks homocysteine-induced endothelial dysfunction in porcine coronary arteries

Magnolol, the main constituent of the stem bark of Magnolia obovata and Magnolia officinalis Rhed., is widely used as a folk remedy for gastrointestinal disorders, cough, diarrhoea, anxiety, and allergic diseases. We investigated the vasorelaxant effect of magnolol on porcine coronary arteries and evaluated its vasoprotective effects. A luminol chemiluminescence test was also used to investigate scavenging capacity of magnolol against homocysteine-induced reactive oxygen species (ROS). Our results reveal that magnolol possesses the ability to induce relaxation of coronary arteries in a concentration-dependent manner, with an IC50 value of 5.78 μM. Treatment with homocysteine markedly increased protein levels of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) in porcine coronary arteries, whereas pretreatment with magnolol suppressed the homocysteine-induced expression of iNOS and COX-2 protein in a concentration-dependent manner. Moreover, the vasorelaxant effect of magnolol was significantly reduced in endothelium-denuded coronary arteries compared with endothelium-intact vessels and was significantly decreased in endothelium-intact arteries in the presence of the NOS inhibitor L-NNA. Magnolol also displayed vasoprotective effects and the ability to scavenge hydrogen peroxide and homocysteine-induced superoxide anions.