Diarylheptanoid-chalcone hybrids with PTP1B and α-glucosidase dual inhibition from Alpinia katsumadai.

The EtOH extracts of the dried seeds of Alpinia katsumadai were revealed with hypoglycemic effects on db/db mice at the concentration of 200 mg/kg. In order to clarify the antidiabetic constituents, 16 new diarylheptanoid-chalcone hybrids, katsumadainols A1-A16 (1-16), together with 13 known analogues (17-29), were isolated from A. katsumadai under the guidance of bioassay. Most of the compounds showed α-glucosidase and PTP1B dual inhibition, among which compounds 1-3, 5-7, 11-14, 21-25, and 27 showed PTP1B/TCPTP selective inhibition with IC50 values ranging from 22.0 to 96.7 µM, which were 2-10 times more active than sodium orthovanadate (IC50, 215.7 µM). All compounds exhibited obvious inhibition against α-glucosidase with IC50 values of 2.9-29.5 µM, indicating 6-59 times more active than acarbose (IC50, 170.9 µM). Study of enzyme kinetics indicated compounds 1, 3, and 12 were PTP1B and α-glucosidase mixed-type inhibitors with Ki values of 13.1, 12.9, 21.6 µM, and 4.9, 7.4, 3.4 µM, respectively.