α-Glucosidase was immobilized on magnetic nanoparticles (MNPs) for selective solid-phase extraction of the enzyme's ligands present in , which is a medicinal plant used for the treatment of various diseases and possesses anti-diabetic activity. One new compound, aloeacone (), together with two known compounds, aloenin aglycone () and aloin A (), were fished out as the enzyme's ligands. The structure of was determined by HR-MS and comprehensive NMR techniques. Compound exhibited a weak inhibitory effect on α-glucosidase, while compounds and were found to possess activation effects on the enzyme for the first time. It is interesting that both an inhibitor and agonists of α-glucosidase were fished out in one experiment.