Antidiabetic andantioxidant properties, and α-amylase and α-glucosidase inhibition effects of triterpene saponins from Piper auritum.

Bioactivity-guided fractionation of methanol extracts from leaves of Piper auritum produced four triterpenoid saponin compounds 1-4. Structures were established based on interpretation of mass spectrometry (MS), nuclear magnetic resonance (NMR) data. 21-(p-methoxycinnamoyl)-olean-12-ene-28oic cid-3-O-α-L-arabinopyranosyl-(1→2)-β-D-glucopyranoside (1) and olean-12-ene-28 methyl ester-3-O-α-L-arabinofuranosyl-(1→2)-β-D-glucopyranoside (2) were orally administered to diabetic mice at dosage of 10 mg/kg of body weight per day for 30 days and resultant biochemical parameters were studied. Both compounds significantly (p<0.05) decreased serum glucose, total cholesterol, and triglyceride levels, compared with controls. Low density lipoprotein and high density lipoprotein cholesterol levels were ameliorated. The effects of lipid peroxidation and oxidative stress in the liver, pancreas, and kidney were reversed, with reductions insulin resistance and stimulation of insulin production. β-Glucosidase activities were studied in vitro. Compounds 1 and 2 can be used to improve glucose and lipid metabolism and to reduce the imbalance between generation of reactive oxygen species and scavenging enzyme activities for prevention of diabetic complications.