Biol. Pharm. Bull. 29(6) 1275—1277 (2006)

caused as lifestyle disease is increasing and has become something of a social problem in recent years. a-Glucosidase inhibitors, medicines that prevent elevation of postprandial blood glucose, can control blood glucose levels without depending on increased secretion of insulin and results in lowering the amount of insulin required after meals. A similar effect to that of these medicines can be expected as a result of a-amylase inhibition. Although the influential factor seems to be an inconsistency in the source of enzyme, we have called attention to aamylase in plasma and gastrointestinal tube of mouse and have surveyed crude drugs and plants that elicit inhibitory activity on this enzyme for the purpose of finding new uses of these materials. In this study, we found that stem bark of Callistemon rigidus (Myrtaceae) intensely inhibits a-amylase activity in isolated mouse plasma in vitro. Consequently, we investigated the active components in this plant and examined the inhibitory effects of these isolated components on a-amylase in mouse gastrointestinal tract in vivo.