In vitro and in vivo inhibitory effect of anthocyanin-rich bilberry extract on α-glucosidase and α-amylase

The inhibition of glycosidase activity is regarded as an effective treatment for diabetes mellitus. Bilberry (Vaccinium myrtillus L.) fruit has a high content of anthocyanins with various biological activities. The objective of this study was to investigate the inhibitory activity of anthocyanin-rich bilberry extract (BE) on alpha-glucosidase and alpha-amylase and their interaction mechanisms in vitro. The IC50 values of BE with regard to alpha-glucosidase and alpha-amylase inhibition were 0.31 +/- 0.02 and 4.06 +/- 0.12 mg/mL, respectively. The enzyme kinetics revealed that BE acts as a mixed-type inhibitor against alpha-glucosidase and alpha-amylase. Moreover, the fluorescence of two glucosidases showed significant quenching by BE. FTIR spectra and differential scanning calorimetry (DSC) indicated that BE changed the enzyme structure and decreased its stability. A morphological observation of starch granules found that BE inhibited the activity of alpha-amylase to postpone the hydrolysis of starch. Furthermore, the in vivo study further showed that BE had a hypoglycaemic effect. The most suitable conformation (main anthocyanidins of BE) and optimal binding site (alpha-glucosidase, alpha-amylase) were assayed by molecular docking. In conclusion, this study revealed that BE could be a potential glycosidase inhibitor.

Automated summary

The study found that bilberry extract had inhibitory activity against alpha-glucosidase and alpha-amylase, acting as a mixed-type inhibitor and changing the enzyme structure and stability. In vivo study also showed a hypoglycaemic effect of bilberry extract. Molecular docking assay indicated that bilberry extract could be a potential glycosidase inhibitor.