Smooth Muscle Relaxant Activity of The Aqueous Leaf Extract of Croton Zambesicus Linn (Euphorbiaceae) In Laboratory Animals
No Thumbnail Available
Date
2014
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Basic & Clinical Pharmacology & Toxicology
Abstract
Croton zambesicus Muell Arg. (Euphorbiaceace) (CZ)
is used by traditional medicine practitioners in Nigeria to treat a variety
of ailments including hypertension. We confirmed the hypotensive
activity in laboratory animals of the aqueous leaf extract of CZ
(unpublished work).
Aim: To determine the smooth muscle relaxant activity and mechanism
of action of the aqueous leaf extract of CZ in laboratory animals.
Methods: The effects of aqueous leaf extract of CZ on spontaneous
contractions of rabbit ileum and on rat ileum precontracted with Ach
(1 lM), angII (1 nM–1 lM), CaCl2 (1–30 mM) and K+ (80 mM)
were determined.
Results: Spontaneous contractions of rabbit ileum were reduced in a
concentration-dependent manner by CZ aqueous extract (3–6 mg/ml)
with a maximal reduction of 70 _ 3 %. In the rat ileum CZ aqueous
extract inhibited AngII-induced contraction in two phases. A Concentration-
dependent inhibition of up to 60 _ 12 % was obtained with
0.6 mg/ml. The second phase inhibition of 98 _ 4 % was obtained
with CZ concentration of 6 mg/ml. This effect was similar to that produced
by valsartan, a non-competitive antagonist of angiotensin 1
receptor (AT1-receptor). Furthermore, KCl-induced contraction was
blocked completely by 0.6 mg/ml CZ leaf extract. CZ extract (1–
6 mg/ml) caused a concentration-dependent inhibition of CaCl2 and
Ach-induced contraction of the rat ileum, with a maximal inhibition of
95 _ 2 % and 80 _ 18 % respectively.
Conclusion: The aqueous leaf extract of CZ has smooth muscle relaxant
activity mediated via inhibition of AT1-receptors and calcium
influx through calcium channels, thus providing a pharmacologic basis
for use of the plant as antihypertensive in traditional medicine. This
study also reveals that CZ acts via multiple pathways, which is in line
with the current therapy for hypertension that encompasses the use of
drugs with complementary mechanisms of action.
Description
Keywords
Croton zambesicus Muell Arg