Effect of triterpene saponins from roots of Ampelozizyphus amazonicus Ducke on diuresis in rats.

Ethnopharmacological Relevance: Ampelozizyphus amazonicus Ducke is a plant used in Brazilian folk medicine to both prevent malaria and act as a depurative.
Aim of the Study: We have investigated the effects of an ethanol crude extract of roots of Ampelozizyphus amazonicus (CEAaD), a chemically characterized saponin mixture (SAPAaD), as well as a saponin-free fraction (SAPAaD-free) obtained from CEAaD on diuresis in rats.
Materials and Methods: Wistar rats under ad libitum water conditions or water deprivation for 12h prior to the start of the experiment were volume-expanded with 0.9% NaCl (4% body weight, by gavage) containing either CEAaD, SAPAaD, or SAPAaD-free at the doses indicated in the text. Rats were individually housed in metabolic cages, and urine volume was measured every 30 min throughout the experiment (3 h).
Results: CEAaD increased urine volume in rats under conditions of both free access to water and under water deprivation. In the latter condition, CEAaD (150 mg/kg) increased the urine volume from zero to 0.9+/-0.1 ml/120 min, n=6). Similarly, the SAPAaD-free (50-200 mg/kg) mixture also increased the urine volume. In contrast, SAPAaD (12.5-1000 mg/kg) produced a significant reduction (p<0.01) in diuresis under conditions of both water deprivation and with free access to water prior to the start of the experiment.
Conclusion: Our data indicate that CEAaD contains compounds that cause both diuresis and antidiuresis and that the antidiuretic effect is due mainly to the presence of saponins.