Viburnum luzonicum Rolfe is widely used in China as folk medicine. The bioactivity evaluation indicated that the n-BuOH fraction of V. luzonicum leaves (VLLB) could significantly inhibit α-amylase and α-glucosidase. In order to clarify its active constituents, the phytochemical analysis on VLLB was first performed using HPLC-QTOF-MS/MS, and three new phenolic compounds, viburosides A-C (1-3), along with seven known analogues (4-10) were isolated through preparative HPLC. The undescribed compounds were determined by extensive spectroscopic analyses ( 1 H and 13 C NMR, HSQC, HMBC, HRESIMS, and ORD) and enzymatic hydrolysis. In the in vitro enzyme assays, compounds 1-8 showed potent α-amylase and α-glucosidase inhibitory activities.The enzymatic kinetics and molecular docking of the strongest inhibitors 2 and 3 against the corresponding target enzyme were also performed.

Viburnum luzonicum is widely distributed in China. Its branch extracts showed potential α-amylase and α-glucosidase inhibitory activities. In order to discover new bioactive constituents, five undescribed phenolic glycosides, viburozosides AÀ E (1 -5), were obtained by bioassay-guided isolation coupled with HPLC-QTOF-MS/ MS analysis. Their structures were elucidated by spectroscopic analyses, including 1D NMR, 2D NMR, ECD, and ORD. All compounds were tested for their α-amylase and α-glucosidase inhibitory potency. Compound 1 showed significantly competitive inhibition against α-amylase (IC 50 = 17.5 μM) and α-glucosidase (IC 50 = 13.6 μM).