Inhibitory effects of Ligustrum robustum (Rxob.) Blume extract on α-amylase and α-glucosidase

• Ligustrum robustum (Rxob.) Blume extract (LRE) had high content of polyphenols.
• LRE showed the remarkable antioxidant activity.
• LRE could inhibit the activity of α-amylase and α-glucosidase effectively.
• LRE could delay the digestion and absorption of glucose in Caco-2 cell monolayer.
• Ligustrum robustum (Rxob.) Blume could be prepared as nutraceuticals.

The α-amylase and α-glucosidase inhibitory effects of Ligustrum robustum (Rxob.) Blume extract (LRE) were investigated and the primary bioactive components were isolated and identified. With high contents of phenols and flavonoids, LRE exhibited remarkable inhibitory effects on α-amylase and α-glucosidase. It also displayed strong antioxidant activity for scavenging free radicals (superoxide and hydroxyl radicals), inhibiting lipid peroxidation and providing reducing power. Moreover, LRE effectively inhibited the catalytic activity of sucrase and maltase in Caco-2 cell monolayer. According to the bioassay-guided isolation and analyses using high-performance liquid chromatography, time-of-flight mass spectrometry, and nuclear magnetic resonance spectroscopy, pomolic acid, tormentic acid, 3-O-cis-p-coumaroyl tormentic acid and 3-O-trans-p-coumaroyl tormentic acid were characterized as the main active constituents. These results suggest that Ligustrum robustum (Rxob.) Blume with a great potential to control postprandial hyperglycaemia might be a novel resource for use in the functional food industry.