Juglans regia L. (walnut) is a plant traditionally used for the treatment of diarrhea. We investigated the antidiarrheal effects of a hydroethanolic leaf extract (HLE) of J. regia against castor oil-induced diarrhea in rats after screening phenolic compounds in the extract. J. regia HLE (0.5, 1, and 2 g\/kg by gavage) produced a dose-dependent delay in the onset of diarrhea compared to the vehicle. It also significantly reduced the number of diarrheal feces, fresh weight and water content of the feces, body weight loss and pain at the two highest doses. Loperamide was effective in inhibiting diarrhea and body weight loss but failed to reduce pain. Our findings show that J. regia HLE has a beneficial effect on diarrhea symptoms and associated pain suggesting that it could be an interesting alternative to standard anti-motility drugs. Flavonoids and hydroxycinnamic acids detected in the extract might explain the effects observed.<\/p>\n\n\n\n