Diuretic activity of some fractions of the epidermis of Poria cocos

Ethnopharmacological relevance: Poria cocos Wolf (Polyporaceae) is a well-known medicinal fungus, the epidermis ("Fu-Ling-Pi" in Chinese) of the sclerotia is used as a diuretic for treating oedema and promoting the diuretic process. In this paper we report on the diuretic activity in rats of petroleum ether, ethyl acetate, n-butanol and the remaining fractions of the ethanol extract from the epidermis of Poria cocos.

Materials and methods: Petroleum ether, ethyl acetate, n-butanol and the remaining fractions of the ethanol extract of Fu-Ling-Pi were orally administered to rats. The urinary excretion rate and the pH and electrolyte excretion were measured in the urine of saline-loaded rats.

Results: In this study, all the tested fractions of Fu-Ling-Pi increased the urinary excretion rate. The three doses of the ethyl acetate fraction all produced remarkable urinary output in 6h, and all produced a remarkable increase in Na(+) excretion and Cl(-) excretion. The Na(+)/K(+) value in the experimental group was significantly enhanced compared with that of the control group, but the three doses of the ethyl acetate fraction had no effect on the K(+) excretion. The 25-mg/kg and 50-mg/kg doses of the n-butanol fraction showed notable urinary output and produced a remarkable increase of Na(+) excretion and Cl(-) excretion, but the two doses did not produce a remarkable effect on the Na(+)/K(+) value. The petroleum ether and remaining fractions did not show remarkable diuretic activities compared with the control group.

Conclusions: This study confirmed that the ethyl acetate and n-butanol fractions present a remarkable diuretic effect, showing that they are the diuretic bioactive fractions of Fu-Ling-Pi. This finding appears to indicate at least two mechanisms for the observed diuretic activity, and the K(+)-saving diuretic effect may be related to the triterpenoid components of intermediate polarity contained in this fungus, particularly the lanostanes tetracyclic triterpenoids.