Bioactivity-directed isolation, identification of diuretic compounds from Polyporus umbellatus.

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AIM OF THE STUDY: Polyporus umbellatus is a fungus used as a diuretic medicine. The objective of this study was to isolate and elucidate the diuretic constituents of n-hexane, ethyl acetate, n-butanol and water extracts of Polyporus umbellatus and to evaluate their diuretic activity.

MATERIALS AND METHODS: The n-hexane, ethyl acetate, n-butanol and water extracts of Polyporus umbellatus were tested by diuretic experiment of normal rats in metabolic cage. The n-hexane extract and n-butanol extract were prepared separately by the bioassay-guided approach. Three isolated compounds doses (5, 10 and 20 mg/kg BW) were orally administered to normal rats. Water excretion rate, pH and content of Na(+), K(+) and Cl(-) were measured in the urine of saline-loaded rats.

RESULTS: n-Hexane extract (P<0.05), n-butanol extract (P<0.05) and three isolated compounds (ergosta-4,6,8(14),22-tetraen-3-one, ergosterol and d-mannitol) displayed diuretic activity.

CONCLUSIONS: The ergosta-4,6,8(14),22-tetraen-3-one was the strongest diuretic constituent in the three compounds. Ergosterol and D-mannitol were found to be also responsible for duiretic effects in Polyporus umbellatus for the first time. Data show that 20 mg/kg dose of the ergosterol for urine out put became significantly higher than in the control rats, but the ratio of Na(+)/K(+) almost unaltered in the three doses. The highest dose of the D-mannitol was significant and increased the cumulative urine output. Regarding the electrolyte excretion, data show that the doses 10 and 20 mg/kg produce significant increase for excretion of Na(+) and Cl(-). The present results provide a quantitative basis explaining application of Polyporus umbellatus as a diuretic medicine. The result proved that its diuretic effects were also due to the contribution of multi-components in clinical application.