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

Abstract

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 R1 (1b), R2–3 (2), R4 (3), S1 (4b), S2 (5), and S3 (6), and five reported phenylethanoid glycosides (7–11). In the bioactivity test, (Z)-osmanthuside B6 (11) displayed strong fatty acid synthase (FAS) inhibitory activity (IC50: 4.55 ± 0.35 μM) as the positive control orlistat (IC50: 4.46 ± 0.13 μM), while ligurobustosides R4 (3) and S2 (5), ligupurpuroside B (7), cis-ligupurpuroside B (8), ligurobustoside N (9), osmanthuside D (10), and (Z)-osmanthuside B6 (11) showed stronger ABTS radical scavenging activity (IC50: 2.68 ± 0.05~4.86 ± 0.06 μM) than the positive control L-(+)-ascorbic acid (IC50: 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.