Abstract The pericarp of Trapa natans L., an annual aquatic floating herb belonging to Lythraceae family, is used as a folk medicine in China. In this study, extracts of Trapa natans pericarp were tested both in vitro and in vivo through a high-fat diet with a single medium dosage streptozotocin injection induced type 2 diabetic mice. Different solvent extracts of Trapa natans pericarp showed α-amylase and α-glucosidase inhibitory activity. After four weeks administration, the ethyl acetate extract of Trapa natans pericarp (50 and 100 mg/kg b.w.) reduced fasting blood glucose level, ameliorated oral glucose tolerance and insulin resistance, improved serum lipids alterations in type 2 diabetic mice as well. Additionally, ethyl acetate extract significantly elevated the insulin receptor substrate 1 and Akt serine/threonine kinase phosphorylation compared to diabetic group. HPLC-MS and HPLC-DAD analysis showed that the ethyl acetate extract was rich in hydrolysable tannins. Results support the notion that Trapa natans pericarp extract has a potential hypoglycemic activity.

ABSTRACT Folium Eriobotryae, the dried leaves of loquat (Eriobotrya japonica, (Thunb.) Lindl., Rosaceae), is a traditional Chinese medicine used to treat cough with phlegm in China. Fallen and growing loquat leaves were tested for their effect on coughing and expectoration in mice. HPLC-ELSD and HPLC-MS analyses of aqueous and ethanol extracts of fallen or growing leaves were used to identify the chemical components responsible for this effect. Both the aqueous and ethanol extracts of growing and fallen leaves of loquat contained antitussive and expectorant activities. Moreover, an aqueous extract of growing loquat leaves with a higher flavonoid content displayed a stronger expectorant activity while the ethanol extract of fallen loquat leaves that contained a higher content of triterpenoid acids induced a stronger antitussive activity.