Inhibition of salivary and pancreatic α-amylases by a pinhao coat (Araucaria angustifolia) extract rich in condensed tannin

The purpose of the present work was to investigate the possible inhibitory effect of a pinhao coat extract rich in condensed tannin on the activity of alpha-amylases (human salivary and porcine pancreatic). Experiments with the classic alpha-amylase inhibitor acarbose and a condensed tannin from Acacia mearnsii were done for comparative purposes. Fourier transform-infrared spectroscopy analysis of the pinhao coat tannin revealed a higher proportion of procyanidins to prodelphinidins when compared to the A. mearnsii tannin. The pinhao coat extract rich in condensed tannin was an effective inhibitor of both human salivary and porcine pancreatic alpha-amylase. Inhibition was of the mixed S-parabolic I-parabolic type. For the human salivary alpha-amylase the inhibition constants were 56.88 +/- 5.74 and 103.27 +/- 11.85 mu g/L; for the porcine pancreatic alpha-amylase the inhibition constants were smaller, namely, 20.25 +/- 1.97 and 46.79 +/- 4.57 mu g/L The decreasing potency sequence was: acarbose > pinhao coat extract rich in tannin > A. mearnsii tannin. Similarly to acarbose and the A. mearnsii tannin, the pinhao coat extract was also effective in diminishing the post-prandial glycemic levels in rats after starch administration. The inhibitory properties of the pinhao coat extract indicate that it can be used to suppress postprandial hyperglycemia in diabetic patients. (c) 2013 Elsevier Ltd. All rights reserved.