Antihyperglycemic effect of fresh Opuntia dillenii fruit from Tenerife (Canary Islands)

The fresh fruit of Opuntia dillenii (Ker-Gawl.) Haw. is used as an antidiabetic agent in Canary Islands folk medicine. To determine whether or not there is a scientific basis for this popular use, the effects of the fruit's red palatable juice on blood glucose levels were assessed in normoglycemic and alloxan-induced diabetic rabbits. Single, or repeated (once a day for 7 consecutive days) oral doses (5 ml/kg) of the juice did not alter blood glucose levels in either normoglycemic or alloxan-induced diabetic rabbits. Instead, a single oral dose reduced significantly the percent increase of glucose-induced hyperglycemia in both normoglycemic and alloxan-induced diabetic rabbits. In normoglycemic rabbits, the hypoglycemic effect of the juice was comparable to that of an oral dose of tolbutamide (100 mg/kg) under the same oral glucose-tolerance conditions; however, the juice did not increase glucose-induced plasma insulin levels. Moreover, the antihyperglycemic effect of the drug was not detected when rabbits received the glucose load intravenously. These data suggest that O. dillenii produces hypoglycemia mainly by reducing intestinal absorption of glucose, but other different mechanisms of action cannot be excluded, for example the presence of an orally active insulin-like compound. During the oral toxicity study of the crude drug, rats given doses up to 50 ml/kg exhibited no symptoms of toxicity.