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.