Bioactive Profiling and Anti-Hyperglycemic Potential of Berberis nummularia Bunge: Role of Polyphenols and α-Amylase Inhibition

The <i>Berberis nummularia</i> fruit is rich in polyphenols and which are associated with the inhibition of carbohydrate-digesting enzymes. However, the phytochemical compositions, antioxidant strength, and the ability of the fruits on the inhibition of α-amylase to control postprandial blood glucose remained elusive. In this study, therefore, different concentrations of ethanol were used in ultrasound processing at 70 °C for 1 h to obtain the crude polyphenol of <i>B. nummularia</i> fruit (CPB) and obtain the purified polyphenol (PPB) using AB-8 macroporous resin. After this, the polyphenolic constituents within PPB were identified using LC-MS/QTOF and investigated for anti-hyperglycemic properties by sucrose loading test. The results showed that the optimal extraction yield (44.32 ± 2.08%) of CPB was achieved with 30% ethanol and the PPB from CPB was reached at 71.88 ± 2.74%. A total of 30 polyphenols including 13 phenolic acids, 13 flavonoids, 3 benzaldehyde derivatives, and 1 aromatic acid were identified, in which the caffeic acid had the highest content (426.20 ± 0.18 ng/mg). The PPB displayed potent α-amylase inhibitory activity with an IC₅₀ value of 69.91 μg/mL and kinetic analysis via Lineweaver-Burk double reciprocal plots confirmed a non-competitive inhibition mechanism. Moreover, at an administration dose of 100 mg/kg body weight (BW), PPB significantly reduced blood glucose levels by 13.75 ± 0.87% and exerted a marked ameliorative effect on postprandial hyperglycemia in vivo. Therefore, these findings provide a foundation for considering PPB as a beneficial functional food ingredient and a potential dietary supplement for the management of postprandial hyperglycemia.