Monoterpenoid Glycosides from the Leaves of Ligustrum robustum and Their Bioactivities

Abstract

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), α-glucosidase, α-amylase, and the antioxidant effects. Compound 2 showed stronger FAS inhibitory activity (IC50: 2.36 ± 0.10 μM) than the positive control orlistat (IC50: 4.46 ± 0.13 μM), while compounds 1, 2, 5 and 11 displayed more potent ABTS radical scavenging activity (IC50: 6.91 ± 0.10~9.41 ± 0.22 μM) than the positive control L-(+)-ascorbic acid (IC50: 10.06 ± 0.19 μM). This study provided a theoretical basis for the leaves of L. robustum as a functional tea to treat obesity.

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

“…The fresh leaves of L. robustum were agitated and baked at 120 °C for 50 min and then smashed. The raw powder (7.0 kg) was extracted with 70% ethanol (28 L × 1) under reflux in a multi-function extractor for 2 h [ 13 ]. The ethanol extract was percolated and condensed in vacuo to gain a paste (2.2 kg).…”

“…The hydrolyzed solution was filtered and condensed. The monosaccharides in the condensed solution were affirmed by TLC (EtOAc- MeOH-HOAc-H 2 O, 8:1:1:0.7, 2 developments) with authentic samples [ 13 ]. The R f values of D-mannose, D-glucose, and L-rhamnose were 0.46, 0.43, and 0.73, respectively.…”

“…The inhibitory effects on FAS, α -glucosidase and α -amylase, and the DPPH and ABTS radical scavenging activities of compounds 1 – 11 were determined by the reported methods [ 12 , 13 , 18 , 19 ], while orlistat, acarbose, and L-(+)-ascorbic acid were applied as the positive controls, respectively ( Supplementary Material S1 ).…”

“…Blume (Oleaceae), classified as a food by the Chinese Ministry of Health since 2011, has been used as Ku-Ding-Cha in Southwest China [ 4 , 5 ]. In the previous investigations on L. robustum [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 ], more than 60 chemical constituents, including monoterpenoid glycosides, phenylethanoid glycosides, phenylmethanoid glycosides, iridoid glycosides, flavonoid glycosides, lignan glycosides, and triterpenoids, were discovered, and the antioxidative, anti-obesity, and anti-inflammatory effects of the aqueous extract, the inhibitory activities on FAS, α -glucosidase, and α -amylase, and the antioxidant effects of some constituents, were observed. To further elucidate the active components for preventing obesity and diabetes, the phytochemical and biological study on the leaves of L. robustum , which had been performed preliminarily [ 12 , 13 ], was carried out.…”

“…In the previous investigations on L. robustum [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 ], more than 60 chemical constituents, including monoterpenoid glycosides, phenylethanoid glycosides, phenylmethanoid glycosides, iridoid glycosides, flavonoid glycosides, lignan glycosides, and triterpenoids, were discovered, and the antioxidative, anti-obesity, and anti-inflammatory effects of the aqueous extract, the inhibitory activities on FAS, α -glucosidase, and α -amylase, and the antioxidant effects of some constituents, were observed. To further elucidate the active components for preventing obesity and diabetes, the phytochemical and biological study on the leaves of L. robustum , which had been performed preliminarily [ 12 , 13 ], was carried out. As a result, 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 ) ( Figure 1 ) were isolated from the leaves of L. robustum .…”