Soluble dietary fibres decrease ?-glucosidase inhibition of epigallocatechin gallate through affecting polyphenol-enzyme binding interactions

The effects of soluble dietary fibres (SDFs) on alpha-glucosidase inhibition of EGCG were studied. Three arabinox-ylans and polygalacturonic acid (PGA) significantly decreased inhibitory activity of EGCG against alpha-glucosidase, while two beta-glucans hardly affected the inhibition. Although arabinoxylans and PGA weakened the competitive inhibition character of EGCG, they maintained the fluorescence quenching effect of EGCG. Then, arabinoxylans and PGA significantly decreased the particle size and turbidity of EGCG-enzyme complex. These results suggest that there formed SDFs-EGCG-enzyme ternary complexes. The stronger decreasing-effects of arabinoxylans and PGA on alpha-glucosidase inhibition of EGCG than beta-glucans resulted from the stronger non-covalent interactions of arabinoxylans and PGA with EGCG. This is considered to arise from the short-branches of arabinoxylans that provided more opportunity for capturing EGCG, and from the strong polarity of PGA carboxyl that promoted hydrogen bondings with EGCG. Conclusively, SDFs should be considered as an impact factor when evaluating alpha-glucosidase inhibition of dietary polyphenols.

Automated summary

The study investigated the effects of soluble dietary fibres (SDFs) on the alpha-glucosidase inhibition of EGCG. It was found that three arabinoxylans and polygalacturonic acid (PGA) significantly decreased the inhibitory activity of EGCG against alpha-glucosidase, while two beta-glucans had little effect on the inhibition. The arabinoxylans and PGA weakened the competitive inhibition character of EGCG but maintained the fluorescence quenching effect.