F.C. Nwinyi, S.O. Aniagu, N.M. Enwerem, J.I. Okogun, K.S. Gamaniel
The aqueous extract of the leaves of Andrographis paniculata (Family: Acanthaceae) was prepared and tested on gastrointestinal smooth muscles of mice, rats and rabbits. The median lethal dose (LD50) of the extract was determined. The effects of the extract on rat ileum, rabbit jejunum, rat stomach fundus strip and mice gastrointestinal motility were evaluated. The LD50 value in mice was 950 mg/kg i.p. Low concentrations of the extract (1.0 �?¢�?�?��?�?? 4.0 mg/ml) relaxed the isolated rat ileum and rabbit jejunum but did not alter the intrinsic myogenic contraction of the isolated rat stomach fundus strip. Higher concentrations of the extract (8.0 �?¢�?�?��?�?? 32.0 mg/ml) produced a concentration �?¢�?�?��?�?? dependent contraction of the same tissues. Lower doses of the extract (16 �?¢�?�?��?�?? 32 mg/kg p.o.) reduced mice gastrointestinal motility while the higher doses (64 �?¢�?�?��?�?? 500 mg/kg p.o) increased the motility. The contractile effects of acetylcholine (5 ng/ml) and histamine (2.0 �?Ž�?¼g/ml; 0.04 mg/ml) were blocked by the lower concentrations of the extract (4.0 mg/ml; 2.0 mg/ml) on both rat ileum and rabbit jejunum. Atropine (0.25 �?¢�?�?��?�?? 1.0 �?Ž�?¼g/ml) reduced the contractile activity of the higher concentration of the extract (16.0 mg/ml) on rat stomach fundus strip while mepyramine (0.25 �?¢�?�?��?�?? 1.0 �?Ž�?¼g/ml) blocked the contractile activity of higher concentrations of the extract (16.0 mg/ml) on the same tissue. The studies suggest that the aqueous extract of Andrographis paniculata exhibited biphasic effects on the gastrointestinal smooth muscles which may be attributable to different mechanisms. These effects may influence the therapeutic dose(s) and application of Andrographis paniculata in the treatment of different ailments.
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