Screening and separation of α-amylase inhibitors from Solanum nigrum with amylase-functionalized magnetic graphene oxide combined with high-speed counter-current chromatography

A screening method using alpha-amylase-functionalized magnetic graphene oxide combined with high-speed counter-current chromatography was proposed and utilized to screen and separate alpha-amylase inhibitors from extract of Solanum nigrum. The alpha-amylase-functionalized magnetic graphene oxide was characterized and found to demonstrate satisfactory structure, magnetic response (24.5 emu/g), and reusability (retained 90% of initial activity after five cycles). The conditions for the screening with alpha-amylase functionalized magnetic graphene oxide were optimized and set at pH 7.0 and 25 degrees C. As a result, two potent flavonoid compounds, apigenin-7-O-glucuronide (1) and astragalin (2), were separated and collected through high-speed countercurrent chromatography and subjected to high-performance liquid chromatography analysis with purity higher than 90% (according to HPLC data), which were identified as alpha-amylase inhibitors. These results suggested that utilization of alpha-amylase functionalized magnetic graphene oxide in the rapid screening and isolation bioactive compounds from complex natural products is a feasible and environmentally friendly method.