Effect of Curcuma longa L. extract and curcumin on porcine pancreatic α-amylase structure and activity

This work aimed to evaluate alpha-amylase activity and structure in the presence of Curcuma longa L. extracts obtained with deep eutectic solvent (DES) and curcumin. Isothermal titration calorimetry (ITC), fluorescence, circular dichroism (CD), and molecular docking were applied to study the effect of additives on enzyme activity and structure. Results showed that in the presence of turmeric extracts, there was a lower catalytic rate. Through the ITC analysis, a lower reaction rate was noticed, related to the inhibition of the enzymatic activity, both in the presence of the extract and of curcumin. The turmeric extracts interacted with the enzyme by a static mechanism as demonstrated by fluorescence. CD showed an increase in negative bands characteristic of hydrophobic interactions between the enzyme and the samples, which probably difficult the access of substrate to the enzyme's active site. Molecular docking showed that curcumin is capable to interact with the active site of alpha-amylase confirming results obtained by other techniques. Results presented in this work show the turmeric extracts potential for alpha-amylase inhibition which may be of interest to the pharmaceutical and food industry.