Pharmacological effects of Hypoxis hemerocallidea Fisch. & C. A. Mey. (Hypoxidaceae) Corm ("African Potato") aqueous extract on some mammalian extra-vascular smooth muscles in vitro.
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Extracts of Hypoxis hemerocallidea corm (African potato) are commonly used by some traditional health practitioners in KwaZulu-Natal Province of South Africa for an array of human ailments. This study was, therefore, undertaken to investigate the GIT spasmolytic, bronchospasmolytic, uterolytic and vasa deferentia relaxant effects of Hypoxis hemerocallidea corm aqueous extract. Respectively, these effects were determined on both naive and spasmogenevoked contractions of the guinea-pig and rat isolated ileum, trachea, uterine horns and the vas deferens in vitro. Healthy, young adult, male and female Dunkin-Hartley guinea-pigs (300-400g) and Wistar rats (250-350g) were used in this study. The isolated tissues were prepared and mounted in Ugo Basile organ-baths under normal physiological conditions. After an equilibration period of 30-45 minutes, the isolated smooth tissue segments were challenged with graded concentrations of Hypoxis hemerocallidea corm aqueous extract, and/or reference drugs. Changes in tension developed by the muscle preparations (relaxations and contractions) were recorded isometrically by means of Ugo Basile's force-displacement transducers and pen-writing 'Gemini' recorders. Relatively low to high concentrations of Hypoxis hemerocallidea corm aqueous extract (APE, 25-400 mg/ml) produced dose-dependent and significant (p<0.05) relaxations of the guinea-pig ileum, and the uterine horns taken from non-pregnant rats, as well as on spasmogenprovoked contractions of stilboesterol-primed, oestrogen-dominated, non-pregnant rats in a concentration-related manner. Potassium chloride (40 mM)-induced contractions of uterine horns, ACh (0.1-3.2 ug/ml)-induced increases in the amplitude of contractions of the guinea-pig ileum, as well as noradrenaline (0.2-1.6 ug/ml)-induced increases in the amplitude of contractions of the male rat isolated vasa diferentia, were significantly (p<0.05-0.001) reduced or abolished by bathapplied APE (25-400 mg/ml). Relatively low to high concentrations of the extract (25-400 mg/ml) caused concentration-dependent increases in the relaxations of the guinea-pig isolated tracheal smooth muscles. Inhibitions of ACh (0.1-3.2 ug/ml)-induced contractions of the guineapig isolated ileum probably suggests possession of antidiarrhoeal activity of APE. Results of this study show pronounced relaxant effects of Hypoxis hemerocallidea corm aqueous extract on guinea-pig vas deferens. The study also lends pharmacological credence to the folkloric, ethnomedical uses of APE as a natural antenatal remedy for threatening abortions, as an antidiarrhoeal remedy, and as a bronchorelaxant. The precise mechanisms of APE action on the smooth muscles could not be established in the present study. However, the uterolytic action of the corm's extract is unlikely to be mediated via ^-adrenoceptor stimulation, but probably mediated through a non-specific spasmolytic mechanism.