Diuretic, Natriuretic and Ca2+-Sparing Effects Induced by Rosmarinic and Caffeic Acids in Rats

This study aimed to investigate the possible diuretic effect in rats of two widely distributed bioactive compounds, rosmarinic and caffeic acids, derived from plants used in popular medicine, as well as to demonstrate their effects against in vitro calcium oxalate crystallization. Male Wistar rats were orally treated with vehicle, hydrochlorothiazide, rosmarinic acid, or caffeic acid. The volume and the urinary parameters were evaluated at the end of 8 h. The antiurolithiatic effect of the compounds was verified in vitro. Treatment with rosmarinic acid (3 mg/kg) or caffeic acid (10 mg/kg) significantly increased urine volume when compared with vehicle-treated rats, an effect associated with augmented urinary Na+ excretion. Interestingly, while rosmarinic acid showed a K+-sparing effect, caffeic acid significantly increased urinary K+ excretion, similarly to the group treated with hydrochlorothiazide (10 mg/kg). The two compounds showed a Ca2+-sparing effect. Therefore, the in vitro analysis of urinary calculi revealed that rosmarinic acid and caffeic acid, in concentrations ranging from 0.03 to 0.3 mg/ml, reduced the number of monohydrate and dihydrate forms of calcium oxalate crystals formed in the urine, suggesting a potential antiurolithiatic effect of these compounds.