The use of Euphorbia hirta L. (Euphorbiaceae) in diarrhea and constipation involves calcium antagonism and cholinergic mechanisms.

Euphorbia hirta (Linn) family Euphorbiaceae has been used in indigenous system of medicine for the treatment of gastrointestinal disorders. This study was designed to determine the pharmacological basis for the medicinal use of E. hirta in diarrhea and constipation.

The aqueous-methanol extract of whole herb of E. hirta (EH.Cr) and its petroleum ether (Pet.EH), chloroform (CHCl₃.EH), ethyl acetate (Et.Ac.EH) and aqueous (Aq.EH) fractions were tested in the in-vivo experiments using Balb/c mice, while the in-vitro studies were performed on isolated jejunum and ileum preparations of locally bred rabbit and Sprague Dawley rats, respectively, using PowerLab data system.

Qualitative phytochemical analysis showed the presence of alkaloids, saponins, flavonoids, tannins, phenols, cardiac glycosides, while HPLC of EH.Cr showed quercetin in high proportion. In mice, EH.Cr at the dose of 500 and 1000 mg/kg showed 41 and 70% protection from castor oil-induced diarrhea, respectively, similar to the effect of quercetin and loperamide, while at lower doses (50 and 100 mg/kg), it caused an increase in the fecal output. In loperamide-induced constipated mice, EH.Cr also displayed laxative effect with respective values of 28.6 and 35.3% at 50 and 100 mg/kg. In rabbit jejunum, EH.Cr showed atropine-sensitive inhibitory effect in a concentration-dependent manner, while quercetin and nifedipine exhibited atropine-insensitive effects. Fractions of E. hirta also produced atropine-sensitive inhibitory effects except Pet.EH and CHCl₃.EH. On high (80 mM) and low (20 mM) K⁺ - induced contractions, the crude extract and fractions exhibited a concentration-dependent non-specific inhibition of both spasmogens and displaced concentration-response curves of Ca⁺⁺ to the right with suppression of the maximum effect similar to the effect quercetin and nifedipine. Fractions showed wide distribution of spasmolytic and Ca⁺⁺ antagonist like effects. In rat ileum, EH.Cr and its fractions exhibited atropine-sensitive gut stimulant effects except Pet.EH.

The crude extract of E. hirta possesses antidiarrheal effect possibly mediated through Ca⁺⁺ antagonist like gut inhibitory constituents, while its laxative effect was mediated primarily through muscarinic receptor agonist like gut stimulant constituents. Thus, these findings provide an evidence to the folkloric use of E. hirta in diarrhea and constipation.