Phenylethanoid and Phenylmethanoid Glycosides from the Leaves of Ligustrum robustum and Their Bioactivities

The phytochemical study on the leaves of Ligustrum robustum, which have been used as Ku-Ding-Cha, led to the isolation and identification of three new phenylethanoid glycosides and three new phenylmethanoid glycosides, named ligurobustosides R(1) (1b), R(2–3) (2), R(4) (3), S(1) (4b), S(2) (5), and S(3) (6), and five reported phenylethanoid glycosides (7–11). In the bioactivity test, (Z)-osmanthuside B(6) (11) displayed strong fatty acid synthase (FAS) inhibitory activity (IC(50): 4.55 ± 0.35 μM) as the positive control orlistat (IC(50): 4.46 ± 0.13 μM), while ligurobustosides R(4) (3) and S(2) (5), ligupurpuroside B (7), cis-ligupurpuroside B (8), ligurobustoside N (9), osmanthuside D (10), and (Z)-osmanthuside B(6) (11) showed stronger ABTS radical scavenging activity (IC(50): 2.68 ± 0.05~4.86 ± 0.06 μM) than the positive control L-(+)-ascorbic acid (IC(50): 10.06 ± 0.19 μM). This research provided a theoretical basis for the leaves of L. robustum as a tea with function in treating obesity and diabetes.