Spasmogenic Activity of Butanolic Leaf Extract of Spondias mombin in Isolated Uterine Muscle of the Rat: Role of Calcium

Objective: To investigate the role of calcium [Ca²⁺] on uterine muscle contraction induced by butanolic leaf extract of Spondias mombin (Anacardiaceae). Materials and methods: Dried leaves of S.mombin were exhausively extracted with n-hexane and 80% ethanol. The 80% ethanol extract was partitioned in dichloromethane, ethyl acetate, butanol, and water. The butanolic extract was tested for spasmogenicity on isolated uterine muscle strips of the rat using conventional methods. Results: The extract contracted the uterine muscle concentration-dependently (EC₅₀, 0.08 mg/ml). The responses to the extract (0.14 mg/ ml) were abolished in Ca²⁺-free media with or without EGTA and by verapamil (0.18 μg/ml). The contractions were similarly abolished by LaCl₃ but significantly (P<0.05) attenuated by amiloride ( 72 μmol). The extract altered the pattern of contraction induced by high K⁺ depolarization (20 mmol) from fast phasic to a tonic contracture. Both isoprenaline (0.1 μmol) and salbutamol (0.1 μmol) inhibited the extract induced contractions which were reversed by propranolol (0.03 μmol). Conclusion: Butanolic leaf extract of S. mombin contracts uterine muscle of the rat primarily through voltage-dependent extracellular Ca²⁺ entry channel.