Hypoglycemic effect of the water extract of Smallantus sonchifolius (yacon) leaves in normal and diabetic rats

The hypoglycemic effect of the water extract of the leaves of Smallantus so nchifolius (yacon) was examined in normal, transiently hyperglycemic and st reptozotocin (STZ)-induced diabetic rats. Ten-percent yacon decoction produ ced a significant decrease in plasma glucose levels in normal rats when adm inistered by intraperitoneal injection or gastric tube. In a glucose tolera nce test, a single administration of 10% yacon decoction lowered the plasma glucose levels in normal rats. In contrast, a single oral or intraperitone al administration of yacon decoction produced no effect on the plasma gluco se levels of STZ-induced diabetic rats. However, the administration of 2% y acon tea ad libitum instead of water for 30 days produced a significant hyp oglycemic effect on STZ-induced diabetic rats. After 30 days of tea adminis tration, diabetic rats showed improved body (plasma glucose, plasma insulin levels, body weight) and renal parameters (kidney weight, kidney to body w eight ratio, creatinine clearance, urinary albumin excretion) in comparison with the diabetic controls. Our results suggest that yacon water extract p roduces an increase in plasma insulin concentration. (C) 2001 Elsevier Scie nce Ireland Ltd. All rights reserved.