Chemical Constituents from the Leaves of Ligustrum robustum and Their Bioactivities

The leaves ofLigustrum robustumhave been consumed as Ku-Ding-Cha for clearing heat and removing toxins, and they have been used as a folk medicine for curing hypertension, diabetes, and obesity in China. The phytochemical research on the leaves ofL. robustumled to the isolation and identification of two new hexenol glycosides, two new butenol glycosides, and five new sugar esters, named ligurobustosides X (1a), X1(1b), Y (2a), and Y1(2b) and ligurobustates A (3a), B (3b), C (4b), D (5a), and E (5b), along with seven known compounds (4aand6–10). Compounds1–10were tested for their inhibitory effects on fatty acid synthase (FAS), α-glucosidase, and α-amylase, as well as their antioxidant activities. Compound2showed strong FAS inhibitory activity (IC504.10 ± 0.12 μM) close to that of the positive control orlistat (IC504.46 ± 0.13 μM); compounds7and9revealed moderate α-glucosidase inhibitory activities; compounds1–10showed moderate α-amylase inhibitory activities; and compounds1and10displayed stronger 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) ammonium salt (ABTS) radical scavenging effects (IC503.41 ± 0.08~5.65 ± 0.19 μM) than the positive controll-(+)-ascorbic acid (IC5010.06 ± 0.19 μM). This study provides a theoretical foundation for the leaves ofL. robustumas a functional tea to prevent diabetes and its complications.Keywords:Ligustrum robustum;hexenol glycoside;butenol glycoside;sugar ester;FAS;α-glucosidase;antioxidant;antiobesity;hypoglycemic