Three New Glycosides from the Leaves of Ligustrum robustum and Their Antioxidant Activities and Inhibitory Effects on Fatty Acid Synthase, α ‐Glucosidase, and α ‐Amylase

In the phytochemical study of the leaves of Ligustrum robustum, two new monoterpenoid glycosides named ligurobustosides V (1a), V₁ (1b), and a new secoiridoid glycoside named ligurobustoside W (2), together with three known glycosides (3-5), were isolated and identified by spectroscopic and chemical methods. The biological research discovered, compounds 3 and 4 showed powerful fatty acid synthase inhibitory activity (half inhibitory concentration [IC₅₀]: 4.21 ± 0.16-4.51 ± 0.12 µM); compounds 1, 4, and 5 displayed some α-glucosidase inhibitory activity; compounds 1-5 revealed some α-amylase inhibitory activity; compounds 1, 3, and 4 showed stronger 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt radical scavenging effect (IC₅₀: 3.98 ± 0.01-6.80 ± 0.07 µM) than L-(+)-ascorbic acid (IC₅₀: 10.06 ± 0.19 µM). Compounds 1, 3, and 4 were considered as some functional constituents of L. robustum to prevent diabetes mellitus and its complications.