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The muscle relaxant properties of Portulaca oleracea are associated with high concentrations of potassium ions

Habtemariam, S and Harvey, A L and Waterman, P G (1993) The muscle relaxant properties of Portulaca oleracea are associated with high concentrations of potassium ions. Journal of Ethnopharmacology, 40 (3). pp. 195-200. ISSN 0378-8741

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Abstract

The juice and aqueous extracts from the plant Portulaca oleracea have been used in West Africa for a variety of medical purposes, and extracts were previously shown to have muscle relaxant properties on isolated nerve-muscle preparations. We have attempted to characterise the components responsible for this activity. Ethanolic extracts caused an initial augmentation of twitch height in chick biventer cervicis preparations and then blockade which appeared to be mediated by an action directly on muscle fibres rather than on neuromuscular transmission. Solvent fractionation of the crude ethanolic extract followed by bioassay on the chick biventer cervicis preparation showed that muscle paralysis increased with increasing polarity: i.e. water fraction > butanol > ethyl acetate approximately equal to crude extracts. These fractions contained 28%, 18%, 12.2% and 9%, respectively, of potassium by weight of dried extract. Similar concentrations of KCl reproduced the same effect as the extracts on muscle activity, and when the most active fraction (water fraction) was desalted, it had no neuromuscular activity even at 10 times higher concentration than used previously. We conclude that the neuromuscular activity of extracts of Portulaca oleracea is caused by high concentrations of potassium ions.