Lignan and phenolic glycosides from Viburnum betulifolium fruits and their α‑amylase and α-glucosidase inhibitory activities.

The phytochemical investigation on the methanol extract of Viburnum betulifolium fruits resulted in the isolation and identification of two new lignan constituents (1 and 2) and seven known phenolic glycosides (3-9). The structures of new isolates, including their absolute configurations were elucidated by extensive spectroscopic analyses (1H and 13C NMR, HSQC, HMBC, HRESIMS, and ECD) and chemical methods. In the in vitro enzyme assays, compounds 1, 2, 6, and 8 showed potential α‑amylase and α-glucosidase inhibitory activities. Among them, compound 1 exhibited stronger inhibitory effects towards α-amylase and α-glucosidase with the IC50 values of 12.68 and 15.17 μM, respectively, than those of the positive control acarbose (IC50, 29.19 and 18.15 μM, respectively). In addition, the molecular docking analyses of compound 1 with strongest inhibition against the target enzymes were also performed.