Investigation of the laxative, spasmolytic and prokinetic properties of aqueous methanol extract of Buxus sempervirens Linn (Buxaceae)

Purpose: To investigate the spasmolytic and laxative properties of Buxus sempervirens Linn (Buxaceae) in rabbits and mice. Methods: Aqueous methanol extract (AqMeBS) as well as the dichloromethane (DCMF) and aqueous (AqF) fractions of Buxus sempervirens were investigated on isolated rabbit jejunum to explore its antispasmodic effect, relative to the standard drug, verapamil. Laxative and prokinetic potentials of 250 and 500 mg/kg doses of AqMeBS extract were evaluated in mice and compared to that of negative (normal saline) and positive (carbachol) control groups. The effects of AqMeBS and carbachol were also tested in mice pretreated with atropine (10 mg/kg). Single dose, acute oral toxicity study on AqMeBS was also executed in mice at 4000, 8000 and 12000 mg/kg doses. Results: AqMeBS, DCMF and AqF significantly inhibited the rhythmic contractility of jejunum with 0.961, 0.0327 and 0.242 mg/mL, respectively, as median effective concentrations (EC50). In addition, AqMeBS, DCMF and AqF significantly relaxed the contractions due to K+, with EC50 of 1.85, 0.05 and 1.07 mg/mL, respectively. Ca2+ concentration response curves (CCRCs) were shifted to the right by AqMeBS and DCMF, in the same manner as verapamil. In the in vivo experiments, AqMeBS produced significant (p < 0.0001) laxative and prokinetic effects at 250 and 500 mg/kg doses and was comparable to that of carbachol. The acute toxicity study showed that AqMeBS was associated with one mortality at the highest tested dose (12000 mg/kg). Conclusion: These results provide the pharmacological basis for the traditional use of B. sempervirens Linn as a laxative and prokinetic remedy in the management of constipation.