Isolation and Identification of<i>α</i>-Glucosidase Inhibitors from Tochu-cha (<i>Eucommia ulmoides</i>)

Abstract

alpha-Glucosidase inhibitory activity was found in aqueous methanol extracts of tochu-cha, dried leaves of Eucommia ulmoides (Eucommiaceae). Five active principles against yeast enzyme were isolated and characterized. Among them, quercetin (1, Ki: 8.5 x 10(-6) M) was considered to contribute mostly to the activity of the tochu leaves. In regard to an animal alpha-glucosidase, rat intestinal sucrase activity was also inhibited by 1.