Proceedings of The Physiological Society
University of Manchester (2010) Proc Physiol Soc 19, PC92
The mechanism of actions of crude extract of leaves from Cymbopogon citratus and citral on the isolated rabbit ileum
C. D. Ramachandran1, S. Si Mui2, R. Ismail1
1. Physiology, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia. 2. Pharmacology, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia.
Cymbopogon citratus (C.citratus) or lemongrass has been reported to be useful in treating gastrointestinal discomforts. Citral, its major constituent has been claimed to exhibit other medicinal properties (1). Our previous study had shown that citral and the methanolic extract of leaves from C. citratus (CLE) relax spontaneous, ACh- and/or KCl-induced contractions in rabbit ileum. Therefore, the aim of this study is to investigate the possible mechanisms involved in the relaxation of ileal smooth muscle by CLE and citral. In this study, we have focused mainly on the involvement of calcium ion and nitric oxide. Ileal strips from rabbits were mounted in the organ bath containing Tyrode’s solution. Subsequently, KCl (80mM) was added followed by verapamil (0.01-3.0µM) (a well known calcium channel blocker), CLE (0.1-10.0mg/ml) and citral (1:64-1:4, v/v dilution) separately. The involvement of Ca2+ movement was studied by incubating the tissues in a calcium-free medium followed by addition of the test substances individually. Then CaCl2 solution, ranging from 0.03-30mM, was added. Meanwhile, the involvement of nitric oxide in the spasmolytic effects of the test substances was tested in the presence and absence of L-NAME (2). All the data were presented as mean ± S.E.M. of n= 6 rabbits for each experiment. Statistical significance was estimated by the Student’s t-test for paired observations and p value < 0.05 was regarded to be significant. Our results showed that the KCl-induced contraction was dose-dependently relaxed, from 0.87±3.41% to 82.48±12.84%, 0.91±2.20% to 89.88±10.06% and 13.60±0.03% to 90.34±0.01% by CLE, citral and verapamil, respectively (p<0.05). The contraction induced by calcium in the calcium-free Tyrode’s solution was decreased by up to 42.6% and 88.06% in the presence of CLE and citral, respectively, and completely abolished by verapamil. The spasmolytic activity of citral at 1:64-1:4 was reduced in the presence of L-NAME from 20.59±7.31% to 6.93±8.26%. However, the relaxation effect of crude extract of leaves was not affected by L-NAME. In conclusion, these findings provide evidence that the relaxation induced by CLE and citral may be via blockade of calcium entry. In addition, nitric oxide pathway may involve in the relaxation induced by citral.
Where applicable, experiments conform with Society ethical requirements