Diuretic and potassium-sparing effect of isoquercitrin-an active flavonoid of Tropaeolum majus L

Aim of the study Previous studies have shown that the extracts obtained from Tropaeolum majus L. exhibit pronounced diuretic effects supporting the ethnopharmacological use of this plant as diuretic. In the present work, phytochemical investigation, guided by bio-assay in spontaneously hypertensive rats (SHR), was carried out in order to identify the compounds responsible for diuretic action. Material and methods Chromatographic fractionation of the hydroethanolic extract yielded an active fraction (TMLR) rich in isoquercitrin. TMLR (25–100 mg/kg) and isoquercitrin (5–10 mg/kg), as well the reference drug hydrochlorothiazide (10 mg/kg) were orally administered in a single dose or daily for 7 days to SHR. The urine excretion rate, pH, density, conductivity and content of sodium (Na+) and potassium (K+) electrolytes were measured in the urine of saline-loaded animals. Results The urinary excretion rate was dose-dependently increased in both TMLR and isoquercitrin groups, as well as Na+. Despite the changes in urinary excretion of electrolytes, the plasmatic levels of Na+ and K+ had not been changed. In addition, we did not find any evidence of renal toxicity or other adverse effects in these animals, even after prolonged treatment with TMLR or isoquercitrin. Conclusion This research supports and extends the ethnomedicinal use of T. majus as diuretic. This activity seems to be associated to the presence of the flavonol isoquercitrin.