Monoterpenoid Glycosides from the Leaves of Ligustrum robustum and Their Bioactivities

The leaves of Ligustrum robustum have been applied as Ku-Ding-Cha, a functional tea to clear heat, remove toxins, and treat obesity and diabetes, in Southwest China. The phytochemical research on the leaves of L. robustum led to the isolation and identification of eight new monoterpenoid glycosides (1-8) and three known monoterpenoid glycosides (9-11). Compounds 1-11 were tested for the inhibitory activities on fatty acid synthase (FAS), alpha-glucosidase, alpha-amylase, and the antioxidant effects. Compound 2 showed stronger FAS inhibitory activity (IC50: 2.36 +/- 0.10 mu M) than the positive control orlistat (IC50: 4.46 +/- 0.13 mu M), while compounds 1, 2, 5 and 11 displayed more potent ABTS radical scavenging activity (IC50: 6.91 +/- 0.10 similar to 9.41 +/- 0.22 mu M) than the positive control L-(+)-ascorbic acid (IC50: 10.06 +/- 0.19 mu M). This study provided a theoretical basis for the leaves of L. robustum as a functional tea to treat obesity.