Abstract
The inhibitory effect of an extract of guava leaves (GvEx) on the activities of sugar-degrading enzymes such as α-amylase and sucrase, in combination with acarbose or voglibose, was studied. Acarbose and voglibose were used at concentrations that inhibited the activity of α-amylase and sucrase by approximately 50%, respectively. Addition of GvEx to the reaction system in combination with the respective enzymes-sugars increased the degree of inhibition of each enzyme activity. To confirm these in vitro effects, an in vivo study was undertaken using normal ICR mice loaded with either cooked starch (1g/kg) and sucrose (2g/kg). The GvEx (250mg/kg) was administrated together with acarbose or voglibose at a dose that prevented the increase in the postprandial blood glucose level. The GvEx had no effect on the blood glucose-lowering effect of the drugs. However, when GvEx was administered to mice loaded with a high concentration cooked starch (without sucrose) together with acarbose or voglibose at a dose that failed to prevent the increase of the postprandial blood glucose level, there was a significant reduction in the rise of the blood glucose level. These results suggest that GvEx is useful for preventing the increase in the blood glucose level in combination with both acarbose and voglibose without having to increase the dose of these drugs. Furthermore it is emphasized that the use of GvEx jointly with acarbose and voglibose has no adverse toxic effects.
