Impact of B-Ring Substitution and Acylation with Hydroxy Cinnamic Acids on the Inhibition of Porcine α-Amylase by Anthocyanin-3-Glycosides

Julia A H Kaeswurm; Lisa Könighofer; Melanie Hogg; Andreas Scharinger; Maria Buchweitz

doi:10.3390/foods9030367

Impact of B-Ring Substitution and Acylation with Hydroxy Cinnamic Acids on the Inhibition of Porcine α-Amylase by Anthocyanin-3-Glycosides

Foods. 2020 Mar 21;9(3):367. doi: 10.3390/foods9030367.

Authors

Julia A H Kaeswurm¹, Lisa Könighofer¹, Melanie Hogg¹, Andreas Scharinger², Maria Buchweitz¹

Affiliations

¹ Institute of Biochemistry and Technical Biochemistry, Department of Food Chemistry, University of Stuttgart, 70569 Stuttgart, Germany.
² Chemisches und Veterinäruntersuchungsamt Karlsruhe, Weißenburger Str. 3, 76187 Karlsruhe, Germany.

Abstract

An inhibitory effect on α-amylase and α-glucosidase is postulated for polyphenols. Thus, ingestion of those secondary plant metabolites might reduce postprandial blood glucose level (hyperglycemia), which is a major risk factor for diabetes mellitus type II. In addition to a previous study investigating structure-effect relationships of different phenolic structures, the effect of anthocyanins is studied in detail here, by applying an α-amylase activity assay, on the basis of the conversion of 2-chloro-4-nitrophenyl-4-O-ß-galactopyranosyl maltoside (GalG₂CNP) and detection of CNP release by UV/Vis spectroscopy and isothermal titration calorimetry (ITC). All anthocyanin-3-glucosides showed a mixed inhibition with a strong competitive proportion, K_ic < 134 µM and K_iu < 270 µM; however, the impact of the B-ring substitution was not statistically significant. UV/Vis detection failed to examine the inhibitory effect of acylated cyanidins isolated from black carrot (Daucus carota ssp. Sativus var. Autrorubens Alef.). However, ITC measurements reveal a much stronger inhibitory effect compared to the cyanidin-3-glucoside. Our results support the hypothesis that anthocyanins are efficient α-amylase inhibitors and an additional acylation with a cinnamic acid boosts the observed effect. Therefore, an increased consumption of vegetables containing acylated anthocyanin derivatives might help to prevent hyperglycemia.

Keywords: acylated anthocyanins; black carrot anthocyanins; inhibition kinetics; isothermal titration calorimetry (ITC); non-acylated anthocyanins; α-amylase.