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

Two undescribed phenolic glycosides, trochinenols B and C (1 and 2), together with four known analogues (3-6), were isolated from the functional tea Trollius chinensis Bunge and their alpha-glucosidase inhibitory kinetics and mechanisms were investigated. It was found that 1 inhibited alpha-glucosidase in a noncompetitive manner with an IC50 value of 25.96 mu M, while 3 showed a notable inhibitory effect against alpha-glucosidase in an uncompetitive manner with an IC50 value of 3.14 mu M. Analysis of synchronous fluorescence and circular dichroism spectroscopy indicated that the binding of 1 to alpha-glucosidase led to the rearrangement and conformational alteration of the alpha-glucosidase enzyme. Furthermore, molecular docking indicated that 1 had a high affinity close to the active site pocket of alpha-glucosidase and indirectly inhibited the catalytic activity of the enzyme. However, 3 was bound to the entrance part of the active center of alpha-glucosidase and could hinder the release of the substrate as well as the catalytic reaction product, eventually suppressing the catalytic activity of alpha-glucosidase.