Screening and identification of DPP-4 inhibitors from Xiaokean formula by a fluorescent probe

Fluorescent bio-probes have attracted increasing attentions in studies for screening bioactive compounds from traditional Chinese medicines. In this study, a new-type fluorescent probe with the function of aggregation-induced emission (AIE) was used to screen dipeptidyl peptidase-4 (DPP-4) inhibitor from Xiaokean formula, which has been clinically used for the treatment of type 2 diabetes mellitus. Potential DPP-4 inhibitors were screened by the fluorescent probe, with diprotin A as the positive control; totally 43 components were isolated from Xiaokean formula by systematic separation. The results showed that 13 components can exert inhibitory effects on DPP-4 activity; 16 compounds were further identified by liquid chromatography-mass spectrometry (LC-MS) from those active components. The inhibitory effects of 14 compounds were further verified, while five of them showed significant inhibition against DPP-4. Salvianolicacid C, ginsenoside Rg₅ and timosaponin AI inhibited DPP-4 activity at the concentration of 5-50 μmol•L⁻¹ in a dose-dependent manner. Thus, our study provided a successful example for screening bioactive compounds from traditional Chinese medicines by using a novelfluorescent probe.