Context: Cactus pear (Opuntia ficus-indica (L.) Mill. (Cactaceae)) is a medicinal plant widely used to treat diabetes. Objective: This work investigates the hypoglycemic and antihyperglycemic effect of cactus pear seed oil (CPSO), its mechanism of action, and any toxic effects. Materials and methods: The hypoglycemic effect of CPSO was evaluated in groups of six healthy Wistar rats given 1 or 2 ml kg À1 orally and compared with groups receiving glibenclamide (2 mg kg À1 ) or water. Glycemia was determined after 30, 60, 120, 240, and 360 min. The antihyperglycemic effect of CPSO was determined in healthy rats and in streptozotocin-induced diabetic rats (STZ); normal rats received 0.8 ml kg À1 CPSO, while diabetic rats received 1 ml kg À1 CPSO, their controls received water or 2 mg kg À1 glibenclamide. For the antihyperglycemic effect evaluation, all the animals were fasted for 16 h before treatment and received glucose orally at 1 g kg À1 30 min after treatment; blood was taken after 30, 90, 150, and 210 min. Intestinal glucose absorption was estimated in rat jejunum perfused with a solution containing 5.55 mmol l À1 glucose. Acute toxicity was determined in albino mice that received oral or intraperitoneal doses of 1, 3, or 5 ml kg À1 CPSO. Results: CPSO (p.o.) decreased postprandial hyperglycemia (60 min after glucose loading), 40.33% and 16.01%, in healthy and STZ-diabetic glucose-loaded rats, respectively. CPSO, also, significantly decreased intestinal glucose absorption by 25.42%. No adverse effects were seen in mice administered CPSO at up to 5 ml kg
À1. Conclusion: CPSO is antihyperglycemic. The effect can be explained partly by inhibition of intestinal glucose absorption.