In Vitro Uterotonic Activity of Launea taraxacifolia(wild) Fractions

Abstract

IntroductionLaunea taraxacifolia(LT) is traditionally used by some native populations of Nigeria to ease labor pains and augment labor thereby facilitating childbirth. A previous study has reported the uterotonic property of the aqueous whole plant extract on isolated uterus of pregnant rats with activity involving oxytocin receptors. The aim of this study was to further validate this activity by evaluating the in‐vitrouterotonic effect of three different fractions of the plant on uterine strips of pregnant female Sprague‐Dawley rats in order to determine the most active fraction(s).MethodThe whole plant of Launea taraxacifolia plant was dried to constant weight and 45g sequentially fractionated using solvents of increasing polarity, i.e n‐Hexane, Ethyl acetate and Methanol. The percentage yield was calculated. The uterotonic property was investigated in vitro using rat uterine strips of rats in late pregnancy (Day18‐20 of gestation). Each pregnant rat was anaesthetized, the uterus removed, cleaned of the connective tissues and cut into strips of about 1 cm in length. Each strip was mounted in an organ bath of 25 ml capacity containing De Jalon physiological salt solution maintained at 37°C and continuously aerated with carbon dioxide and oxygen (5% carbon dioxide + 95% oxygen air mixture). The tissues were allowed to equilibrate for 30 min and normal myometrial contractions were recorded at baseline. Uterine contractile responses were elicited by adding oxytocin (0.17, 0.34, 0.68, 1.36 and 2.72 µg/ml), acetylcholine (4, 8, 16, 32, 64 µg/ml), n‐hexane, ethyl acetate and methanol fractions of LT (80, 160, 320, 640, 1280, 2560 and 5120 µg/ml) organ bath concentrations. Each concentration was allowed to act for 5 mins and the amplitude of contraction recorded by means of an isotonic transducer for three repeated experiments. Data were analyzed using Student t‐test. p<0.05 was considered significant. Dose‐response curves were plotted as displacement from baseline (cm) and percentage of maximal response against logarithm concentrations using Graph pad prism (version 8.3). The EC50 (i.e concentration causing 50% of maximal response) values were estimated by non‐linear curve fitting.ResultsThe methanol fraction gave the highest yield (3.37, 4.56 and 5.09%w/w for n‐hexane, ethyl acetate and methanol respectively). The methanol fraction showed a significant concentration dependent contraction of the uterine strips at 160, 320, 640, 1280, 2560 and 5120 µg/ml with the maximal response obtained at 1280 µg/ml (Figure 1). The n‐Hexane and ethyl acetate fractions did not produce contraction of the uterine strips but rather resulted in a relaxation of the uterine strips. On the other hand, oxytocin and acetylcholine produced a significant contraction at all the concentrations used. Furthermore, when compared to standard agonists, the EC50 obtained were 1270, 2144 and 17859 µg/ml for oxytocin, acetylcholine and LT methanol fraction respectively. The dose response curve of the percentage maximal response versus logarithm concentration was also shifted to the right (Figure 2).ConclusionThe methanol fraction of Launea taraxacifolia possess some uterotonic activity which are absent in the n‐Hexane and Ethyl acetate fractions. This suggests that the uterotonic compounds present in Launea taraxacifolia could be isolated from the methanol fraction.