Anti-hyperglycemic effect of chebulagic acid from the fruits of Terminalia chebula Retz

Abstract

In the present study, we firstly compared rat intestinal α-glucosidase inhibitory activity by different ethanol-aqueous extractions from the dried fruits of Terminalia chebula Retz. The enzymatic assay showed that the 80% ethanol extract was more potent against maltase activity than both 50% and 100% ethanol extracts. By HPLC analysis, it was determined that the 80% ethanol extract had a higher content of chebulagic acid than each of 50% or 100% ethanol extract. Next, we investigated how efficiently chebulagic acid could inhibit sugar digestion by determining the glucose level on the apical side of the Caco-2 cell monolayer. The result showed that the maltose-hydrolysis activity was down-regulated by chebulagic acid, which proved to be a reversible inhibitor of maltase in Caco-2 cells. On the other hand, chebulagic acid showed a weak inhibition of sucrose-hydrolysis activity. Meanwhile, chebulagic acid did not have an obvious influence on intestinal glucose uptake and was not effective on glucose transporters. Further animal studies revealed that the oral administration of chebulagic acid (100 mg/kg body weight) significantly reduced postprandial blood glucose levels by 11.1% in maltose-loaded Sprague-Dawley (SD) rats compared with the control group, whereas the oral administration of chebulagic acid did not show a suppressive effect on postprandial hyperglycemia in sucrose- or glucose-loaded SD-rats. The results presented here suggest that chebulagic acid from T. chebula can be used to control blood glucose and manage type 2 diabetes, although clinical trials are needed.

Keywords: Terminalia chebula; anti-hyperglycemia; chebulagic acid; α-glucosidase inhibitor.

Figure 1

Maltose-hydrolysis inhibitory activity of rat intestinal α-glucosidase by 50–80% ethanol extracts from the fruits of Terminalia chebula Retz.

Figure 2

HPLC-DAD chromatograms of 50–100% ethanol extracts from the fruits of Terminalia chebula Retz. (A), 50% ethanol extract; (B), 80% ethanol extract; (C), 100% ethanol extract.

Figure 3

Results of the maltose hydrolysis assay with the Caco-2 monolayer in the presence of chebulagic acid (0.05–0.5 mM/well). PGG, 1,2,3,4,6-penta-O-galloyl-β-d-glucose (0.5 mM/well) as a positive control.

Figure 4

Results of the sucrose hydrolysis assay with the Caco-2 monolayer in the presence of chebulagic acid (0.05–0.5 mM/well). Baicalein, 5,6,7-trihydroxyflavone (0.05 mM/well) as a positive control.

Figure 5

Maltose-hydrolysis activity in the Caco-2 monolayer pretreated with chebulagic acid (0.05–0.5 mM/well) for 20 min at 37 °C in 5% CO₂ atmosphere.

Figure 6

Glucose uptake in the Caco-2 monolayer in the presence of chebulagic acid (0.05–0.5 mM/well).

Figure 7

Anti-hyperglycemic effects of chebulagic acid on SD-rats. Fasted rats were given 2 g/kg of maltose (A), 2 g/kg of sucrose (B) and 2 g/kg of glucose (C), with or without 100 mg/kg of chebulagic acid (■) and vehicle (control: ◆). Acarbose (○) was used as a positive control for maltose-loaded SD-rats (A). Data are presented as the mean ± SD (n = 5). ^* p < 0.05 vs. control.

Figure 7

Anti-hyperglycemic effects of chebulagic acid on SD-rats. Fasted rats were given 2 g/kg of maltose (A), 2 g/kg of sucrose (B) and 2 g/kg of glucose (C), with or without 100 mg/kg of chebulagic acid (■) and vehicle (control: ◆). Acarbose (○) was used as a positive control for maltose-loaded SD-rats (A). Data are presented as the mean ± SD (n = 5). ^* p < 0.05 vs. control.