Hesperetin and diosmetin, but not hesperidin and diosmin, dose-dependently (10–100 µM) and reversibly inhibited acetylcholine (1 µM) and KCl (80 mM) induced contractile activity. The antispasmodic effect of hesperetin was partially blocked by 4-aminopyridine (100 µM), glibenclamide (100 µM) and NG-nitro-L-arginine methyl ester (L-NAME, 100 µM). By contrast, apamin (0.1 µM), tetraethylammonium (500 µM) and methylene blue (10 µM) did not affect the magnitude of hesperetin-induced myorelaxant effect. Indomethacin (10 µM) increased the force of hesperetin-evoked reaction.
In conclusion, hesperetin and diosmetin are potent myorelaxant agents. The antispasmodic effect of hesperetin is partially mediated by fast current low-voltage activated K+ channels, voltage-independent K+ channels and involves the nitric oxide pathway. Finally, hesperetin shows a synergistic effect with indomethacin towards jejunal KCl-precontracted smooth muscle.