Evaluation of the diuretic activity in two Mexican medicinal species: Selaginella nothohybrida and Selaginella lepidophylla and its effects with ciclooxigenases inhibitors.

BACKGROUND

Doradilla is a plant that has a long history in the Mexican traditional system of medicine for gall and renal stones, diuresis, stomach and liver inflammation among other diseases. Major components isolated from these plants include biflavonoids as amentoflavone (1), robustaflavone (2) and (S)-2,3-dihydrorobustaflavone (3) and the carbohydrate trehalose (4). The aim of this study was to evaluate the diuretic effect of the decoction of Selaginella nothohybrida Valdespino and Selaginella lepidophylla (Hook & Grev) Spring (Selaginellaceae), and compounds 1-4. We also explored the probable mode of action comparing the effects when using nonspecific and specific COX׳s inhibitors.

METHODS

Three biflavonoids (1-3) were isolated from the ethyl acetate extraction of the aqueous decoction and the carbohydrate trehalose (4) from the aqueous phase. The structures of all compounds were elucidated by spectroscopic methods and comparisons were made against published data. The diuretic activity was assessed in mice by oral administration of the decoctions in doses of 1000 and 2000mg/kg and biflavonoids 1-3 and trehalose (4) in a dose range of 10mg/kg using furosemide as a standard drug. Inhibitors of COX׳s such as acetyl salicylic acid, sodium naproxen, indomethacin and Celebrex were also assayed to analyze the involvement of renal prostaglandins in diuresis. Water excretion rate, pH, density, conductivity, and contents of Na(+) and K(+) were measured in the urine of mice.

RESULTS

Decoction of Selaginella lepidophylla showed lower effect in the urine output at doses of 1000 and 2000mg/kg, while decoction of Selaginella nothohybrida produced an increase at 2000mg/kg (P<0.05). Urinary electrolytes excretion was also affected by this last extract and pure compounds: decoction diminished urinary excretion of sodium and potassium ions, so as compounds 1 and 4; compounds 2 and 3 observed just a natriuretic effect. Pretreated mice with COX׳s inhibitors and then with test compounds 1, 2, 4 and decoction showed inhibition of diuresis in all cases exception for treatment with trehalose (4); natriuretic effect was observed in all cases except for biflavonoid robustaflavone (2) which behaved as the reference compound furosemide. Selaginella nothohybrida decoction behaved similarly to COX-2 inhibitor Celebrex (8), inhibiting diuresis.

CONCLUSIONS

Selaginella nothohybrida presents a moderate diuretic effect, which appears to be in partly mediated by the presence of biflavonoids and trehalose. Renal prostaglandins may be involved in the mechanism of diuresis. The present results provide a quantitative basis explaining the traditional folk medicine use of Selaginella nothohybrida as a diuretic agent by Mexican population.