Argemone mexicana Linn (family Papaveraceae) is an exotic weed indigenous in South America but has widespread distribution in many tropical and sub-tropical countries including West Africa. Phytochemical screening and toxicity evaluation was carried out on the leaves of this herb. Preliminary phytochemical evaluation of the ethanolic extract revealed the presence of reducing sugars, flavonoids, sterols/terpenes, tannins and alkaloids. Acute toxicity determination also showed the plant to possess an LD50 value of 400mg/kg body weight intraperitoneally in mice with a weight of 18 – 25gm and averagely aged between 4 – 6 weeks. The results of the various phytochemical tests indicated the plant to be rich in various biologically active compounds which could serve as potential source of crude vegetable drugs and in addition the plant is slightly toxic to the experimental model used.

Keywords: Phytochemical constituents, toxicity evaluations, ethanolic extract, Argemone mexicana Linn, leaves