Strategic immobilization of α-amylase on a ZIF-8 nanoplatform for targeted bioactivity screening of Gynura medica extracts.

This study presents an enzyme immobilization strategy utilizing zeolitic imidazolate framework-8 (ZIF-8), a metal-organic framework (MOF) material synthesized in-house, for α-amylase immobilization, establishing a novel solid-phase extraction platform for targeted isolation of enzymatic inhibitors from Gynura medica aqueous extracts. The ZIF-8@α-amylase nanoparticles were prepared using the in situ encapsulation method and exhibited 91% enzyme encapsulation efficiency and enhanced aqueous stability. ZIF-8@α-amylase exhibited a broader operational range, retaining more than 50% activity across 20-70 °C and pH 4.0-9.0 (compared to 20-65 °C and pH 5.5-7.5 for the free enzyme). This immobilized system also demonstrated a high binding capacity of 189.5 mg g-1 for acarbose. Using a mild alkaline buffer for elution, a concentrated fraction showing 18.1% α-amylase inhibition was obtained, which mainly contained phenolic acids, flavonoids, and hydrolyzable tannins as identified by LC-MS/MS. Dose-response analyses demonstrated significant pancreatic amylase inhibition by identified compounds: ellagic acid-4-O-glucoside: 98.86 ± 2.3% (1.0 g L-1), quercetin-3-O-rhamnoside: 66.32 ± 1.9% (1.0 g L-1), and methyl gallate: 33.56 ± 1.2% (1.0 g L-1). Overall, ZIF-8@α-amylase is a promising solid-phase extraction platform for selectively enriching bioactive amylase inhibitors from complex botanical matrices, with potential in pharmaceutical discovery and diabetes management.