In vitro antioxidant activity and antidiabetic effect of fractionated potato protein hydrolysate via ultrafiltration and adsorption chromatography

Potato processing effluents represent a potential source of valuable proteins for the production of bioactive peptides. In this study, potato protein was hydrolyzed with Alcalase and fractionated using ultrafiltration (10, 2 kDa molecular weight cut off) and adsorption chromatography (adsorbent resin XAD-16 column). Potato protein hydrolysates (PHM and PHC), membrane fractions PHR1 ( 10 kDa), PHR2 (2-10 kDa) and PHR3 (<2 kDa) and column fractions PF1 (hydrophilic) and PF2 (hydrophobic) were investigated for antioxidant activity, alpha-glucosidase and alpha-amylase inhibition. In addition, alpha-amylase kinetic inhibition, fluorescence quenching and surface hydrophobicity were evaluated. PF2 fraction showed the best antioxidant activity with the highest ABTS center dot+ scavenging activity, Fe2+ chelating and DPPH center dot scavenging activity. PHR1 was the most active against alpha-amylase whereas alpha-glucosidase activity was weak for all samples. Fluorescence quenching results of alpha-amylase showed higher red shift after interaction with PHR1 than PF2. Higher quenching constant for PHR1 demonstrated higher affinity and interaction between this fraction and the enzyme than PF2. Enzyme kinetic studies revealed that PHR1 and PF2 fractions reduced alpha-amylase activity through uncompetitive and mixed inhibition, respectively. These results demonstrate higher antioxidant activity for hydrophobic fraction and higher alpha-amylase inhibitory activity for high molecular weight fraction of the potato hydrolysates.