Hypoglycemic effect of Hypoxis hemerocallidea corm (African potato) aqueous extract in rats.

Diabetes mellitus has been recognized as a clinical syndrome since ancient times, and remains a crippling global health problem today. It is a group of heterogeneous, autoimmune, hormonal and metabolic disorders, often accompanied by hypertension, hyperlipidemia and obesity. Current estimates suggest that approximately 150 million people worldwide suffer from diabetes mellitus. The present study was undertaken to examine the hypoglycemic effect of aqueous extract of Hypoxis hemerocallidea (family: Hypoxidaceae) corm (locally known as "African Potato") in normal (normoglycemic) and in streptozotocin (STZ)-treated, diabetic rats. Young adult, male Wistar rats weighing 250-300 g were used. Diabetes mellitus was induced in the group of diabetic test rats by intraperitoneal injections of STZ (90 mg/kg). In one set of experiments, graded doses of the aqueous extract of African Potato (100-800 mg/kg p.o.) were administered to 12-h fasted normal and diabetic rats. In another set of experiments, 800 mg/kg of African potato extract, a dose of the plant extract that produced maximal hypoglycemic effects in fasted normal and diabetic rats in our pilot experiments, was used. The hypoglycemic effect of this single dose was compared with those of insulin (5 micro U/kg s.c.) and glibenclamide (5 mg/kg p.o.) in 12-h fasted normal and diabetic rats. Following acute treatment, relatively moderate to high doses of African potato extract (100-800 mg/kg p.o.) produced dose-dependent, significant reductions (p < 0.05-0.001) in the blood glucose concentrations of fasted normal and diabetic rats. Similarly, insulin (5 micro U/kg s. c.) and glibenclamide (5 mg/kg p.o.) produced significant reductions (p < 0.01-0.001) in the blood glucose concentrations of the fasted normal and diabetic rats. At a dose of 800 mg/kg, the plant extract caused 30.20% and 48.54% reductions in the blood glucose concentrations of fasted normal and STZ-treated diabetic rats, respectively. While it is likely that the hypoglycemic effect of the plant extract is largely due to its phytosterols and/or sterolin content, the exact mechanism of its hypoglycemic action is still obscure and will have to await further studies. However, the results of this experimental animal study indicate that African potato possesses hypoglycemic activity; and thus lends credence to the suggested folkloric use of the herb in the control and/or management of adult-onset, type 2 diabetes mellitus in some communities of South Africa.