Inhibitory effects of phenolic glycosides from Trollius chinensis Bunge on α-glucosidase: inhibition kinetics and mechanisms

Two undescribed phenolic glycosides, trochinenols B and C (1 and2), together with four known analogues (3-6), were isolated from the functional tea Trollius chinensis Bunge and their α-glucosidase inhibitory kinetics and mechanisms were investigated. It was found that 1 inhibited α-glucosidase in a noncompetitive manner with an IC₅₀ value of 25.96 μM, while 3 showed a notable inhibitory effect against α-glucosidase in an uncompetitive manner with an IC₅₀ value of 3.14 μM. Analysis of synchronous fluorescence and circular dichroism spectroscopy indicated that the binding of 1 to α-glucosidase led to the rearrangement and conformational alteration of the α-glucosidase enzyme. Furthermore, molecular docking indicated that 1 had a high affinity close to the active site pocket of α-glucosidase and indirectly inhibited the catalytic activity of the enzyme. However, 3 was bound to the entrance part of the active center of α-glucosidase and could hinder the release of the substrate as well as the catalytic reaction product, eventually suppressing the catalytic activity of α-glucosidase.