Cardiovascular and airway relaxant activities of peony root extract

Paeonia emodi (peony) is a well known plant used medicinally to treat hypertension, palpitations, and asthma. Despite its popularity, there are few reports in the scientific literature examining its use in such conditions. We prepared a 70% ethanolic extract of peony root (Pe.Cr) and applied it to segments of guinea pig atria and trachea and rat aorta suspended separately in tissue baths. Activity against arachidonic acid (AA)-induced platelet aggregation was measured in human platelet-rich plasma. Airway relaxant effect was evaluated against acetylcholine (ACh)-induced airway contraction in mouse lung slices loaded with fluo-4. Pe.Cr (0.3-10 mg/mL) showed an atropine-resistant negative inotropic effect in atria. In rat aorta, an endothelium-independent vasodilatory effect (0.3-10 mg/mL) was seen in phenylephrine- and high-K+-induced contractions. Pe.Cr (0.01-1 mg/mL) also inhibited AA-induced platelet aggregation. In isolated trachea, Pe.Cr (0.3-10 mg/mL) relaxed carbachol- and histamine-induced contractions independently of beta-adrenergic receptors. In mouse lung slices, Pe.Cr (0.3-1 mg/mL) inhibited ACh-induced airway narrowing and oscillations of intracellular Ca2+ in airway smooth muscle cells. The results showed cardiosuppressant, vasodilatory, antiplatelet, and tracheal and airway relaxant activities of peony, providing potential justification for its medicinal use in different hyperactive cardiovascular and respiratory disorders.