The relaxing effect of Poncirus fructus and its flavonoid content on porcine coronary artery

Coronary artery disease is a common occurrence in human, and causes enormous social cost. Poncirus fructus (PF), the dried immature fruits of Poncirus trifoliata Rafinesquem, is used in the treatment of womb contraction and dyspepsia, as a prokinetic, and in improving blood circulation. This study was performed to investigate the effects of PF and some of its flavonoids components on the coronary from the pig. The arterial ring was suspended by a pair of stainless steel stirrups in an organ bath. The end of the upper stirrup was connected to an isometric force transducer. A dose-dependent induction of relaxation was observed by both water and 70% ethanol extracts of PF in the porcine coronary artery precontracted with U46619 (100 nM), a stable analogue of the potent vasoconstrictor thromboxane A2. The 70% ethanol extract showed more efficacy than the water extract. Pretreatment of the artery with L-NAME (100 µM), a nitric oxide synthase inhibitor, resulted in a significant reduction in the relaxation induced by PF extract. In addition, ODQ (10 µM), a soluble guanylate cyclase inhibitor, also significantly reduced the effects of PF extracts. Hesperidin, a flavonoid present in PF, induced very weak relaxation of the porcine coronary artery at a high concentration (100 µM), while its aglycone, hesperetin, demonstrated a dose-dependent relaxation. In conclusion, PF extracts induced relaxation in the porcine coronary artery, partially through the nitric oxide-cGMP pathway, and the aglycones of flavonoids might be also involved in the relaxation of the same artery.