Piliostigma reticulatum (Caesalpiniaceae) has been used in traditional medicine for the treatment of gastrointestinal disorders like diarrhea. The aim of the present study was to examine the relaxant activity of an extract of P. reticulatum stem bark and five of its fractions on isolated rabbit duodenum. Segments of duodenum of rabbits were suspended in an organ bath. The ethanol extract had been fractioned to obtain some fractions heptane, dichloromethane, ethyl acetate, butanol and aqueous extract. The ethanol extract and the dichloromethane fraction were tested on the contraction of rabbit duodenum at the increasing concentrations. Increasing concentrations of P. reticulatum ethanol extract and its fraction induced a relaxant effect on spontaneous rabbit duodenum. The ethanol extract reduced duodenum contraction totally at 1.32 mg/mL at IC50 = 0.62 mg/mL. At the test concentration of 0.52mg/mL in organ bath, the dichloromethane fraction showed a relaxation of 100% (IC50 = 0.24 mg/mL). Piliostigma reticulatum stem bark possesses antispasmodic properties that can at least explain and support its traditional use against diarrhea.

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The objective of the present study was to investigate the anticholinergic and adrenergic activities of a dichloromethane fraction of a crude ethanol extract of stem bark of P. reticulatum, on isolated rabbit duodenum contractions. In the first study, the dichloromethane fraction was tested on the isolated rabbit duodenum contractions at increasing concentrations (0.13; 0.26; 0.39 and 0.52 mg/mL) after addition of acetylcholine. In the second study, the dichloromethane fraction was tested on the isolated rabbit duodenum contractions ten minutes after addition of prazosin or propanolol at increasing concentrations (10 -4 , 10 -3 and 10 -2 mg/mL). The amplitude and tone induced by acetylcholine were significantly inhibited by the dichloromethane fraction. At a concentration of 0.52 mg/mL, the amplitude induced by the acetylcholine was 0.42 ± 0.05g. The relaxation induced by the dichloromethane fraction was significantly inhibited by prazosin and propanolol as well. At a concentration of 10 -2 mg/mL, prazosin and propanolol inhibited the relaxation induced by the dichloromethane fraction at rates of 18.6 ± 2.42 and 17.4 ± 0.7 % respectively. Results showed that the dichloromethane fraction of crude ethanol extract of stem bark of Piliostigma reticulatum exhibited anticholinergic and adrenergic properties that could at least explain and back up its traditional use against diarrhea.

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