Analogues of Dihydroflavonol and Flavone as Protein Tyrosine Phosphatase 1B Inhibitors from the Leaves of Artocarpus elasticus .

Protein tyrosine phosphatase 1B (PTP1B) is one of the target enzymes whose disruption leads to obesity and diabetes. A series of PTP1B inhibitors were isolated from the leaves of Artocarpus elasticus , used in traditional medicines for diabetes. The isolated inhibitors ( 1-13 ), including two new compounds ( 1 and 2 ), consisted of dihydroflavonols and flavones. The structural requirements for the PTP1B inhibitory mode and potency were revealed in both skeletons. The two highest PTP1B inhibitory properties were dihydroflavonol 1 and flavone 6 analogs with IC 50 values of 0.17 and 0.79 μM, respectively. The stereochemistry also affected inhibitory potencies: trans isomer 1 (IC 50 = 0.17 μM) vs cis isomer 2 (IC 50 = 2.24 μM). Surprisingly, the dihydroflavonol and flavone glycosides ( 11 and 13 ) displayed potent inhibition with IC 50 s of 2.39 and 0.22 μM, respectively. Furthermore, competitive inhibitor 1 was applied to time-dependence experiments as a simple slow-binding inhibitor with parameters of K i app = 0.064103 μM, k 3 = 0.2262 μM -1 min -1 , and k 4 = 0.0145 min -1 . The binding affinities by using the fluorescence quenching experiment were highly correlated with inhibitory potencies: 1 (IC 50 = 0.17 μM, K SV = 0.4375 × 10 5 L·mol -1 ) vs 3 (IC 50 = 17.79 μM, K SV = 0.0006 × 10 5 L·mol -1 ). The specific binding interactions were estimated at active and allosteric sites according to the inhibitory mode by molecular docking.