Diuretic activity of Smilax canariensis, an endemic Canary Island species

Smilax canariensis is an endemic species of the Canary Islands, popularly known as "Zarzaparrilla sin espinas". This species has wide use in folk-medicine practice on the islands, especially as diuretic. So the aim of our study is to evaluate the diuretic activity of an aqueous and a methanol extract of this species.

Three infusions doses (250, 500 and 750 mg/kg) and two methanol extract doses (100 and 200 mg/kg) were orally administered to laboratory rats. Water excretion rate, pH, density, conductivity, and content of Na(+) and K(+) were measured in the urine of saline-loaded rats.

Water excretion rates were significantly increased in a dose-dependent manner by both hot water infusions and the alcohol extract. The electrolytic excretion was also dose-dependent, although potassium excretion was markedly reduced when using the alcohol extract compared with that observed for the infusion.

Smilax canariensis presents a notable diuretic effect which appeared to be related both to its potassium content and to the presence of polar organic compounds. The present results provide a quantitative basis explaining the traditional folk-medicine use of Smilax canariensis as a diuretic agent by the Canary Island population.