Abstract
Recent studies of Hibiscus sabdariffa Linn. have demonstrated that it presents diuretic, natriuretic, and potassium sparing effects. However, the mechanism that induces these effects has not yet been elucidated. The aim of this study was to explore the possible mechanism of action for the diuretic effect of Hibiscus sabdariffa extract and its fractions.
The aqueous extract from this plant and the fractions obtained with solvents of different polarities were administered to adrenalectomized rats, and the diuretic effect was measured in the presence of deoxycorticosterone acetate (aldosterone analog).
The effect on renal filtration was also evaluated in an in situ kidney model, and finally, the effect of diuretic active extracts on gene expression of the alpha subunit from the transporter (αENaC) of renal epithelial cell was quantified. The subsequent results were obtained: The aqueous extract of Hibiscus sabdariffa presented the following chemical composition, 32.4 mg/g delphinidin-3-O-sambubioside, 11.5 mg/g cyanidin-3-O-sambubioside, 11.5 mg/g quercetin, and chlorogenic acid 2.7 mg/g. The concentration of anthocyanins was diminished until disappearance due to decrease of the polarity of the solvents used in the extraction process, in contrast to the flavonoids and chlorogenic acid, which had their concentration increased. The diuretic effect caused by adrenalectomy in rats was reversed by deoxycorticosterone acetate activity. However, the effect of deoxycorticosterone acetate was antagonized by spironolactone, the aqueous extract of Hibiscus sabdariffa, and the acetonitrile : methanol 5 : 5 mixture extract, administered orally. A similar effect was observed on renal filtration obtained from the isolated kidney model.
When the gene expression levels of αENaC was measured in adrenalectomized rats, it was observed that spironolactone, the aqueous extract of Hibiscus sabdariffa, the acetonitrile : methanol 5 : 5 mixture, as well as the acetonitrile extract significantly decreased the expression of this protein.
The conclusion of this work is that the diuretic, natriuretic, and potassium sparing effects of Hibiscus sabdariffa are due in part to the modulation of aldosterone activity by the presence in the extract of this plant of compounds potentially responsible for this modulation, as anthocyanins, flavonoids, and chlorogenic acid.
Key words
Hibiscus sabdariffa Linn. - Malvaceae - diuretic - aldosterone antagonism
