Phytoconstituents from the leaves of Viburnum cylindricum Buch. -Ham. ex D. Don and their enzyme inhibitory activities

Viburnum cylindricum Buch. -Ham. ex D. Don is abundant in bioactive secondary metabolites with promising functions such as anti-inflammation and anti-diabetes. In this work, the polyphenolic extract of V. cylindricum leaves (VCLP) exhibited significant inhibition on α-glucosidase and urease activity. Two previously undescribed phenolic glycosides (1, 2) and fourteen known analogues (3–16) were isolated from VCLP, which were determined by spectroscopic analyses and chemical methods. The bioactivity assessment revealed that compounds 3, 4, 8, 14, and 16 could potently inhibit α-glucosidase activity with IC50 values ranging from 20.83 to 28.52 μM compared to acarbose (IC50 = 29.71 μM) (p < 0.05). In addition, compounds 3 and 4 showed significant urease inhibition with IC50 values of 10.73 and 7.61 μM, respectively, comparable to thiourea (IC50 = 28.57 μM) (p < 0.05). Moreover, the molecular docking analysis elucidated the binding mechanisms between these bioactive compounds and the enzymes α-glucosidase and urease.