Monoterpenoid Glycosides from the Leaves of Ligustrum robustum and Their Bioactivities (II)

Ligustrum robustum has been not only used as a heat-clearing and detoxicating functional tea (Ku-Ding-Cha) but also consumed as a hypotensive, anti-diabetic, and weight-reducing folk medicine. From the leaves of L. robustum, ten new monoterpenoid glycosides named ligurobustosides T(10) (1a), T(11) (1b), T(12) (2a), T(13) (2b), T(14) (3a), T(15) (3b), F(1) (4b), T(16) (5a), T(17) (5b), and E(1) (6b), together with five known ones (4a, 6a, 7, 8a, 8b), were separated and identified using the spectroscopic method and chemical method in this research. The results of biological tests exhibited that the fatty acid synthase (FAS) inhibitory action of compound 5 (IC(50): 4.38 ± 0.11 μM) was as strong as orlistat (IC(50): 4.46 ± 0.13 μM), a positive control; the α-glucosidase inhibitory actions of compounds 1–4 and 7–8, and the α-amylase inhibitory actions of compounds 1–8 were medium; the ABTS radical scavenging capacities of compounds 1–3 and 5–8 (IC(50): 6.27 ± 0.23 ~ 8.59 ± 0.09 μM) were stronger than l-(+)-ascorbic acid (IC(50): 10.06 ± 0.19 μM) served as a positive control. This research offered a theoretical foundation for the leaves of L. robustum to prevent diabetes and its complications.