Isolation and Antidiarrhoeal Activity of Methyl 9, 10-Dimethoxyanthracene-2-Carboxylate from Morinda lucida Stem Bark: A Potential Ethnomedicinal Lead for Diarrhoea Treatment

Morinda lucida Benth. (Rubiaceae) is widely used in Nigerian ethnomedicine for Diarrhoea treatment. This study aimed to isolate and characterize bioactive compounds from its stem bark and evaluate their antidiarrhoeal efficacy in a mouse model. A compound, identified as methyl 9, 10-dimethoxyanthracene-2-carboxylate, a mono-substituted oral derivative, was isolated from the ethyl acetate fraction using column chromatography and characterized via ¹H and ¹³C NMR spectroscopy. The antidiarrhoeal activity of the ethyl acetate fraction (50 and 100 mg/kg) was assessed in a castor oil-induced gastrointestinal motility test in Wistar albino mice, with loperamide (2 mg/kg) and normal saline (10 mL/kg) as controls (n = 4 per group). The 100 mg/kg dose significantly reduced charcoal meal transit (5.75 cm at 1 hour, 0.00 cm by 4 hours) compared to loperamide (9.25 cm at 1 hour, 0.25 cm at 4 hours) and normal saline (19.50 cm at 5 hours) (p < 0.001, ANOVA). The 50 mg/kg dose showed moderate efficacy (7.00 cm at 2 hours, 0.00 cm by 6 hours). These findings validate the ethnomedicinal use of Morinda lucida and suggest that methyl 9,10-dimethoxyanthracene-2-carboxylate contributes to its antidiarrhoeal effects, warranting further mechanistic and clinical studies for development as a natural therapeutic agent. Keywords: Morinda lucida, anthraquinone, methyl 9,10-dimethoxyanthracene-2-carboxylate, antidiarrhoeal activity, castor oil, ethnomedicine