Antispasmodic Activity of Onion (Allium cepa L.) Peel Extract on Rat Ileum

Onion (Allium cepa) bulb from Liliaceae has antioxidant, spasmolytic and antihypertensive activities. The aim of present study was to investigate the antispasmodic effect of onion peel on rat ileum contractility. Onion peel powder was extracted by maceration in 70% alcohol for 72 h. A terminal portion of ileum from male Wistar rat was dissected and its contractions were recorded isotonically in an organ bath containing Tyrode solution (37°C) under 1 g tension. Extract cumulative concentrations (0.1, 0.2 and 0.4 mg/ml) reduced the ileum contractions induced by KCl (60 mM) and carbachol (10 μM) dose-dependently (P<0.0001). The extract antispasmodic effect was not reduced by tissue incubation with propranolol (1 μM, 30 min), naloxone (1 μM, 30 min), L-NAME (100 μM, 20 min), glibenclamide (10 μM, 5 min) neither by tetraethylammonium (1 mM, 5 min). In Ca2+-free with high K+ (60 mM) Tyrode solution, extract reduced the ileum contractions induced by CaCl2 dose-dependently (P<0.05, P<0.01). Onion peel extract inhibits ileum contractions without involving β-adrenoceptor, opioid receptor, nitric oxide production, and potassium channels activation. It is suggested that quercetin in onion peel extract induces spasmolytic effect via calcium channels.