Phenolic constituents from the fruits of Viburnum urceolatum and their α -glucosidase and α -amylase inhibitory activities

Two previously undescribed p-hydroxyphenyl glycosides, viburceosides A (1) and B (2), together with thirteen known analogues, were isolated from the fruits of Viburnum urceolatum. Their structures were established through comprehensive analysis of spectroscopic (NMR, HRESIMS) spectra and quantum-chemically calculated ECD spectra. The sugar moieties of the new isolates were determined by hydrolysing the glycosides and analysing monosaccharides as chiral derivatives by HPLC. Enzyme inhibition assays showed compound 4 was the most potent constituent, exhibiting dual inhibitory activity on α-glucosidase and α-amylase, with IC₅₀ values of 5.49 μM and 7.63 μM, respectively. These values indicated that compound 4 was of significantly superior potency to acarbose (IC₅₀ = 26.75 μM and 37.31 μM, respectively). Subsequent molecular docking studies provided insights into the binding modes responsible for this enhanced activity.