Potent protein tyrosine phosphatase 1B (PTP1B) inhibiting constituents from Anoectochilus chapaensis and molecular docking studies.

Context: Anoectochilus chapaensis Gagnep. (Orchidaceae), an indigenous and valuable Chinese folk medicine, has been used as an antidiabetic remedy. However, the bioactive constituents have not been reported. Objective: To explore potent protein tyrosine phosphatase 1B (PTP1B) inhibitors from the whole herbs of A. chapaensis for the treatment of diabetes. Materials and methods: The compounds were obtained by PTP1B bioactivity-guided isolation from the active fraction of ethonal extract of A. chapaensis, and elucidated by extensive spectroscopic methods and evaluated for their potential to inhibit PTP1B with a series of doses in dimethyl sulphoxide by a colorimetric assay in vitro. The Autodock program was used to dock the active compounds into the binding sites. Results: Fifteen compounds were identified; epifriedelanol, friedelane, 2 alpha, 3 beta-dihydroxyolean-12-en-23, 28, 30-trioic acid, dibutyl-phthalate, and 7-hydroxy-2-methoxy-9,10-dihydrophenanthrene- 1,4-dione were isolated from the genera Anoectochilus for the first time. All 15 compounds were tested for their inhibitory activity against PTP1B in vitro. Nine active compounds exhibited potent inhibitory effect with IC50 values of 1.16-6.21 mu M, which were comparable with the positive control suramin. The 3D-docking simulations showed negative binding energies of -7.4 to -8.5 kcal/mol and supported a high affinity to PTP1B residues in the pocket site, indicating that they may stabilize the open form and generate tighter binding to the catalytic sites of PTP1B. Discussion and conclusion: The results clearly demonstrated that the potential active constituents from A. chapaensis could inhibit PTP1B, which may be mainly attributed to a combination of triterpenoids and flavonoids.