Unlocking hypoglycemic effect of black highland barley by targeting α-glucosidase inhibitors based on UF-HPLC-MS /MS

Highland barley is a unique crop of the Qinghai-Tibet Plateau, and its hypoglycemic properties have attracted extensive attention from the academic community. However, the key active compound that alleviates postprandial hyperglycemia remains unclear. In this study, UF-HPLC-MS/MS identified 25 potential α-glucosidase (α-G) inhibitors from the acetone extract of bran from 80% black highland barley. Among these, seven compounds (baicalin, breviscapine, luteolin-7-glucuronide, robtin, procyanidin B₂, catechin and epicatechin) with strong anti-α-G potential were selected for further investigation. The results showed that proanthocyanidin B₂ (PB₂) showed the highest α-G inhibitory activity with the IC₅₀ of 0.02 mg/mL. These compounds directly interacted with different active sites on α-G through non-covalent bonds and affected α-G conformation by influencing the microenvironment, thereby inhibiting its activity. The relationship between the inhibitory efficiency and molecular structure showed that the location of -OH on the B ring and the amount of -OH could obviously enhance the anti-α-glucosidase activity. In addition, luteolin-7-glucuronide and acarbose exhibited a stronger synergistic effect on hyperglycemia in vivo. The present study uncovered the active compounds of highland barley for its hypoglycemic effect by targeting α-G, which provided more details for the further utilization of highland barley as functional foods.