New insights into the interactions between dark blue pigment from Vaccinium bracteatum Thunb leaves and digestive enzymes

The dark blue pigment from Vaccinium bracteatum Thunb. leaves (VBTL) is a healthy ingredient for controlling postprandial blood glucose during the stage of dietary carbohydrate digestion. Our previous study has proved that the dark blue pigment has an inhibition effect on pancreatic alpha-amylase. However, the influence on other digestive enzymes (alpha-glucosidases, trypsin, and alpha-chymotrypsin) is still unclear. Therefore, this research evalu-ated the impact of this dark blue pigment on the three digestive enzymes during in-vitro digestion. The effects of dark blue pigment on the activities and conformations of the alpha-glucosidase, trypsin, and alpha-chymotrypsin were confirmed by multi-spectroscopic techniques and molecular docking. The results showed that this pigment possessed a higher inhibition ability on the alpha-glucosidase. The complexes of three enzymes and the pigment all resulted in the changes in fluorescence quenching and secondary structures of these complexes. However, the interactions between two proteolytic enzymes and pigment slightly impacted their activities. Additionally, molecular docking suggested that the complex between alpha-glucosidase and pigment formed hydrogen bonds and hydrophobic interactions in the substrate-binding pocket. These findings provide creative insight into the VBTL dark blue pigment controlling postprandial hyperglycemia without side effects on the proteolytic enzymes.

Automated summary

This research evaluated the impact of the dark blue pigment from Vaccinium bracteatum Thunb. leaves on three digestive enzymes. The results showed that the pigment had a higher inhibition ability on alpha-glucosidase and had minimal impact on proteolytic enzyme activities. Molecular docking suggested the formation of hydrogen bonds and hydrophobic interactions between alpha-glucosidase and the pigment.