Mode of action of escins Ia and IIa and E,Z-senegin II on glucose absorption in gastrointestinal tract

We examined the mode of action of escins Ia (1) and IIa (2) and E,Z-senegin II (3) for the inhibitory effect on the increase in serum glucose levels in oral glucose-loaded rats. Although 1-3 inhibited the increase in serum glucose levels in oral glucose-loaded rats, these compounds did not lower serum glucose levels in normal or intraperitoneal glucose-loaded rats, or alloxan-induced diabetic mice. Furthermore, 1-3 suppressed gastric emptying in rats, and also inhibited glucose uptake in the rat small intestine in vitro. These results indicated that 1-3 given orally have neither insulin-like activity nor insulin-releasing activity. Compounds 1-3 inhibited glucose absorption by suppressing the transfer of glucose from the stomach to the small intestine and by inhibiting the glucose transport system at the small intestinal brush border. (C) 1998 Elsevier Science Ltd. All rights reserved.