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

<i>Viburnum cylindricum</i> 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 <i>V. cylindricum</i> leaves (VCLP) exhibited significant inhibition on <i>α</i>-glucosidase and urease activity. Two previously undescribed phenolic glycosides (<b>1</b>, <b>2</b>) and fourteen known analogues (<b>3</b>-<b>16</b>) were isolated from VCLP, which were determined by spectroscopic analyses and chemical methods. The bioactivity assessment revealed that compounds <b>3</b>, <b>4</b>, <b>8</b>, <b>14</b>, and <b>16</b> could potently inhibit <i>α</i>-glucosidase activity with IC₅₀ values ranging from 20.83 to 28.52 μM compared to acarbose (IC₅₀ = 29.71 μM) (<i>p</i> < 0.05). In addition, compounds <b>3</b> and <b>4</b> showed significant urease inhibition with IC₅₀ values of 10.73 and 7.61 μM, respectively, comparable to thiourea (IC₅₀ = 28.57 μM) (<i>p</i> < 0.05). Moreover, the molecular docking analysis elucidated the binding mechanisms between these bioactive compounds and the enzymes <i>α</i>-glucosidase and urease.