Phytochemical characterization, antioxidant and antidiarrheal activities, and safety profile of Lomariopsis japurensis rhizome extract

Abstract Background Lomariopsis japurensis is a fern traditionally used by Indigenous Amazonian communities for gastrointestinal disorders, including diarrhea; however, experimental evidence supporting this use remains limited. This study evaluated the phytochemical screening, in vitro antioxidant properties, antispasmodic and antidiarrheal activities, and acute oral toxicity of L. japurensis rhizome aqueous extract. Results Phytochemical screening revealed flavonoids, tannins, coumarins, saponins, triterpenoids, and sterols, with high total phenolic and flavonoid contents. The extract exhibited antioxidant activity in different in vitro assays. In isolated mouse ileum, L. japurensis rhizome extract exhibited weak intrinsic contractile activity but reduced responsiveness to acetylcholine. Preincubation with 1.0 mg/mL L. japurensis rhizome extract significantly increased the acetylcholine EC₅₀ from 4.65 ± 1.92 to 20.15 ± 5.77 nM, indicating decreased sensitivity to cholinergic stimulation. In vivo , L. japurensis rhizome extract (2,000 mg/kg) reduced gastrointestinal transit from 71.30 ± 4.87% in the control group to 59.28 ± 3.32%, corresponding to a 16.9% inhibition. LJRE also reduced liquid stools from 3.4 ± 1.0 to 1.0 ± 0.55 in the castor oil-induced diarrhea model, corresponding to a 70.6% reduction. No mortality, treatment-related clinical signs, or macroscopic abnormalities were observed following acute oral administration at doses up to 2,000 mg/kg. Conclusions The present study with LJRE showed antispasmodic and antidiarrheal effects, together with in vitro antioxidant activity and a low acute oral toxicity profile under the experimental conditions evaluated. The marked reduction in liquid stools relative to the more moderate inhibition of gastrointestinal transit suggests that its antidiarrheal activity may involve mechanisms beyond reduced intestinal propulsion. These findings provide experimental support for the traditional use of LJRE for diarrhea and warrant further studies to identify its bioactive constituents and clarify their mechanisms of action.