α‐glucosidase inhibition and the in vivo hypoglycemic effect of butyl‐isobutyl‐phthalate derived from the Laminaria japonica rhizoid

The rhizoid of Laminaria japonica is widely used in Chinese medicine as a treatment for diabetes. Therefore, a bioactivity-tailored isolation and detailed chemical characterization was used to identify the antidiabetes compounds found in the L. japonica rhizoid. Liquid chromatography/mass spectrometry (LC/MS), proton NMR and carbon NMR spectra analyses demonstrated that the active compound was butyl-isobutyl-phthalate (BIP). BIP demonstrated a significant concentration-dependent, non-competitive inhibitory activity against alpha-glucosidase in vitro, with an IC(50) of 38 mu M. In vivo, the ethyl acetate fraction (EAF) and purified BIP displayed a significant hypoglycemic effect in streptozocin-induced diabetic mice. The present study indicates BIP could be considered as an alpha-glucosidase inhibitor and developed as an important antidiabetes agent for type II diabetes therapy. Copyright (C) 2010 John Wiley & Sons, Ltd.