Evaluation of the Diuretic Activity and Phytochemical Screening of Different Solvent Fractions of the Rhizomes of Rumex abyssinicus Jacq (Polygonaceae) in Rats

Rumex abyssinicus J. (Polygonaceae) is a widely spread medicinal plant used traditionally to treat a variety of diseases, including hypertension. Previous study confirmed the diuretic effect of the aqueous and 80% methanol crude extracts of the plant, of which the 80% methanol extract produced a better diuresis. The aim of this study was to investigate which solvent fraction(s) of the 80% methanol extract would be responsible for the diuretic effect of the plant. Diuretic activity was examined in adult male rats, which were orally administered with aqueous, methanol and ethyl acetate fractions of 80% methanol extract of R. abyssinicus at doses of 250, 500 and 750 mg/kg; furosemide (10 mg/kg) or vehicle. Total urine output and electrolyte content of the urine was computed over 24 h period and compared with the standard and negative controls. Phytochemical composition of the fractions was also investigated using standard tests. The methanol (p<0.01) and ethyl acetate (p<0.001) fractions induced a significant diuresis at the lower dose (250 mg/kg) compared to the aqueous fraction, which produced a notable effect only at its higher dose. Both fractions also increased urinary electrolyte excretion significantly (p<0.001) at their highest doses. Whilst the ethyl acetate fraction increased urine output comparably to that of furosemide, the methanol fraction showed the highest saluretic effect. These findings collectively indicate that an increase in urine volume is observed with decreasing polarity of the fractions. This suggests that the diuretic activity of the plant might be mostly due to active principles contained in the less polar fractions.Keywords: Rumex abyssinicus, Furosemide, Diuretic Activity, Electrolytes, Solvent Fraction