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

Ligustrum robustumhas 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 ofL. robustum, ten new monoterpenoid glycosides named ligurobustosides T10(1a), T11(1b), T12(2a), T13(2b), T14(3a), T15(3b), F1(4b), T16(5a), T17(5b), and E1(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 compound5(IC50: 4.38 ± 0.11 μM) was as strong as orlistat (IC50: 4.46 ± 0.13 μM), a positive control; the α-glucosidase inhibitory actions of compounds1–4and7–8, and the α-amylase inhibitory actions of compounds1–8were medium; the ABTS radical scavenging capacities of compounds1–3and5–8(IC50: 6.27 ± 0.23 ~ 8.59 ± 0.09 μM) were stronger thanl-(+)-ascorbic acid (IC50: 10.06 ± 0.19 μM) served as a positive control. This research offered a theoretical foundation for the leaves ofL. robustumto prevent diabetes and its complications.Keywords:Ligustrum robustum;monoterpenoid glycoside;FAS;α-glucosidase;antioxidant;anti-diabetes