Recently, the processing and engineering technology research team of the Institute of Fragrance Drinks of the Chinese Academy of Thermal Sciences has made new progress in the study of the mechanism of synergistic inhibition of α - amylases by pectin and flavonoids . This study analyzed the mechanism of the influence of pectin on the inhibition of α - amylase activity of rutin and quercetin mixture from the aspects of inhibition type, quenching type, fluorescent residue hydrophobicity, enzyme conformation, binding force and binding site.

Postprandial blood sugar levels are closely related to the occurrence of type II diabetes. However, most clinical drugs used to lower glycemics may induce side effects such as bloating, diarrhea and abnormal liver function. It is necessary to find natural and effective alternatives to commercial anti-diabetes drugs. α - amylase is a key hydrolase that plays a key role in carbohydrate hydrolysis. It can hydrolyze starch into maltose, oligosaccharides and a small amount of glucose, and delay postprandial blood sugar levels by inhibiting the activity of α - amylase. Flavonoids can effectively inhibit the activity of α - amylase. In addition to flavonoids, there are also a variety of active substances such as polysaccharides and proteins in food. Understanding the interaction between food components has always been a research hotspot in the academic community. Currently, most studies focus on investigating the effects of polysaccharides on the binding of polyphenol monomers to proteins or enzymes. However, there have been few relevant studies on whether the presence of polysaccharides affects the inhibition of α - amylase activity of flavonoid mixtures .

Therefore, this study used methods such as combined inhibition evaluation, inhibitory kinetics, fluorescence quenching, synchronous fluorescence spectroscopy, three-dimensional fluorescence spectroscopy and isothermal titration calorimetry to explore the effects and mechanism of pectin on the inhibition of α - amylase in flavonoid mixtures. The results show that pectin enhances the inhibition and quenching affinity of rutin - quercetin mixture on α - amylase. Pectin increased the Stern - Wolmer quenching constant of the rutin - quercetin mixture - α - amylase from ( 6.08 ± 0.453 ) × 103 mL/mg to ( 9.80 ± 0.285 ) × 103 mL/mg . Pectin enhances the ability of rutin - quercetin mixture to inhibit α - amylase for two main reasons: on the one hand, because pectin binds to rutin, the opportunity for quercetin to bind to α - amylase activity centers is increased, thereby enhancing the inhibitory effect of rutin - quercetin mixture on α - amylase. On the other hand , pectin and quercetin are simultaneously with α-Different sites of amylase bind to form a ternary complex of pectin - α - amylase - quercetin. The ternary complex changes the conformation of α - amylase and the hydrophobicity of amino acid residues, thereby enhancing the hydrogen bonding effect in the reaction system. In addition, hydrogen bonding between pectin and α - amylase also coordinated the activity of the enzyme. This study provides a new perspective for the screening of α - amylase inhibitors, and also lays the theoretical foundation for the application of rutin, quercetin and pectin in the management of hyperglycemia in functional foods.

The relevant research results were published in the International Journal of Biological Macromolecules under the title " Pectin enhances the inhibition of α -amylase via the mixture of rutin and quercetin " . The research results rely on the Hainan Provincial Key Laboratory for Suitability Processing and Quality Control of Special Tropical Crops, and have been funded by Hainan Provincial Science and Technology Talent Innovation Project, the special project of basic scientific research business fees for central-level public welfare research institutes, the Science and Technology Innovation Team of the National Tropical Agricultural Science Center of the Chinese Academy of Tropical Agricultural Sciences, and the special fund for cassava industry technology system CARS-11 .