Abstract
Methanolic extract of Onosma griffithii and its fractions were evaluated for possible effects on rabbits' jejunum preparations. Rabbits of either sex (weight 1.5-2.0 kg) were used in experiments. Studies were carried out on rabbits' jejunum preparations. Crude methanolic extract of Onosma griffithii (Meth.OG) was tried in concentrations of 0.01, 0.03, 0.1, 0.3, 1.0, 3.0, 5.0 and 10.0 mg/ml on rabbits' jejunum preparations. Meth.OG was also tried on KCl-induced contractions to explain its possible mode of actions in the presence and absence of atropine (0.03 mu M). Fractions of Meth.OG were tried in similar manner. Calcium chloride curves were constructed for Meth.OG treated tissues that were compared with Curves constructed for verapamil in same fashion. Preliminary phytochemical screening of the plant was also performed. Meth.OG increased the amplitude of spontaneous activity of rabbits' jejunum preparations at concentrations of 0.1, 0.3 and 1.0 mg/ml. However, spasmolytic effects were observed at higher concentrations 3.0, 5.0 and 10.0 mg/ml. Mean EC50 values (mg/ml), respectively, in absence and presence of atropine were 7.5 +/- 0.25 (6.9-8.4, n=6) and 3.0 +/- 0.17 (2.3-3.5, n=6, p<0.05). Mean EC50 values, respectively, for effects on spontaneous and KCL-induced contractions were 7.5 +/- 0.25 (6.9-8.4, n=6) and 7.3 +/- 0.35 (6.25-8.2, n=6, p<0.05). n-Hexane, chloroform and ethyl acetate fractions showed their respective EC50 values (mg/ml) 9.7 +/- 0.25 (8.6-10.2, n=6), 4.0 +/- 0.2 (3.5-4.6, n=6) and 1.07 +/- 0.093 (0.78-1.5, n=6). EC50 values for calcium chloride curves in presence of 0.3 mg/ml Meth.OG were - 2.27 +/- 0.038 (- 2.4 to - 2.10, n=6) vs. control - 2.78 +/- 0.04 (-2.9 to - 2.6, n=6, p<0.05) Log [Ca++]M. Comparing with curves of calcium chloride constructed in presence of 0.1 mu M verapamil, the EC50 (log [Ca++] M) values were - 1.82 +/- 0.087 (- 2.0 to -1.65, n=6) vs. control - 2.64 +/- 0.089 (-2.9 to -2.4, n=6) demonstrated a right shift (p<0.05). Meth.OG tested positive for terpenes, saponins, sterols, flavonoids and carbohydrates. We concluded that the relaxant effect of Meth.OG is exerted through blocking of calcium channels. However, n-butanolic and aqueous fractions produced spasmogenic effects that require further work for isolation of pharmacologically active substances.