Inhibition of α-amylases by pentagalloyl glucose: Kinetics, molecular dynamics and consequences for starch absorption

Pentagalloyl-glucose (PGG) occurs in many plants and possesses several therapeutic properties, including anti-diabetic ones. Based on the latter, the inhibitory action of PGG on α-amylases was investigated. PGG inhibited both the pancreatic and the salivary α-amylases. With starch as the substrate, complexation with the free enzyme form either predominates (pancreatic enzyme) or is the only complexation that is effectively allowed (salivary enzyme; competitive inhibition). This contrasts with a previous report on the salivary enzyme showing non-competitive inhibition when a synthetic substrate was used. PGG was less effective than acarbose as an inhibitor of α-amylases and presented a different binding pattern in terms of the aminoacyl residues involved. Finally, PGG also diminished the hyperglycemic excursion normally caused by starch administration when it was given to rats simultaneously to the polysaccharide. This suggests that PGG or foods and infusions rich in PGG could be helpful as adjuvants for maintaining normal glycemia.