Recent Advance on Chemistry and Bioactivities of Secondary Metabolites from Viburnum Plants: An Update.

Viburnum species are a group of small trees or shrubs that are of great ornamental and medicinal values. Some of them have been used for a long time both as conventional and ethnic medicine. Viburnum fruits, eaten in fresh and processed forms, have been revealed to contain various health-promoting nutrients. With the increasing research on Viburnum plants, they are considered to be an abundant resource of bioactive natural products possessing diverse pharmacological properties and unique chemical structures, that is powerfully proved by the existence of structurally novel vibsane-type diterpenoids which only occur in Viburnum species, newly discovered lignan constituents with unusual side chains and other noteworthy natural components. This review describes 185 new and 228 known secondary metabolites from Viburnum genus between 2008 and 2020, including their chemical structures, sources and bioactivities, and highlights the corresponding structure-activity relationships.

LC-MS guided isolation of phenolic glycosides from Viburnum luzonicum Rolfe leaves and their α­amylase and α-glucosidase inhibitory activities.

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 α­amylase 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 (1H and 13C NMR, HSQC, HMBC, HRESIMS, and ORD) and enzymatic hydrolysis. In the in vitro enzyme assays, compounds 1-8 showed potent α­amylase 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.

Two new phenolic allopyranosides and their analogues from the stems of Viburnum luzonicum Rolfe guided by LC-MS.

Two new phenolic allopyranosides, named viburluzosides A and B (1, 2), together with eight known phenolic glycosides (3 - 10) were discovered from the stems of Viburnum luzonicum Rolfe under the guidance of LC-MS analyses coupled with bioactivity evaluation. They were purified through various chromatography methods and identified by extensive spectroscopic analyses (1H and 13C NMR, HSQC, HMBC, and HRESIMS) and chemical methods. The in vitro evaluation on α-glucosidase and aldose reductase (AR) inhibitory activities of isolated compounds were conducted. Compounds 1 - 4 and 6 - 9 exhibited α-glucosidase inhibitory activities with IC50 values of 5.35 - 21.34 µM and AR inhibitory activities with IC50 values of 6.21 - 40.06 µM. Moreover, the inhibitory kinetics analyses of compounds 1 and 2 were also performed.