Anoectochilus chapaensis Gagnep. （Orchidaceae）, an indigenous and valuable Chinese folk medicine, has been widely used in China to treat diabetes. However, few reports are available about its constituents and activity. The present experiment was conducted to investigate the active fractions from A. chapaensis in diabetic rat model induced by high-fat diet plus streptozotocin. The total EtOH extract from the whole herbs ofA. chapaensis, half of which was partitioned in sequence with petrol ether （PE）, ethyl acetate （EtOAc）, n-BuOH and H2O, thus yielding four fractions, all of them were orally administered with an identical dose amount to 4 g/kg dried crude herbs once a day for consecutive two weeks to further investigate the antihyperglycemic activity. The EtOAc fraction caused a significant fall in the non-fasting blood glucose level of diabetic rats from （402.66±82.26） to （226.26±62.10） mg/dl, which may be attributed to ameliorating insulin resistance, modulating the activity of enzymatic antioxidants, reducing the content of NO, etc. Much more intact β cells in the islets of Langerhans in EtOAc fraction-treated groups than the negative control were observed, which greatly supported the morphological and functional elucidation. The OGTT evidenced that EtOAc fraction could promote the endurance capacity of acute glucose increase in diabetic rats. The EtOAc fraction of A. chapaensis contains some hypoglycemic and antioxidant principles with the potential to be developed further for the treatment of diabetes specifically associated with an insulin resistance state.
