Interaction between orange juice and < 1 kDa leaf peptides: effect on the antioxidant and antidiabetic related enzyme inhibitory activities

Abstract

AbstractDesigning a good vehicle for functional ingredients is the major focus of this study. Small molecular weight peptides (< 1 kDa) extracted from amaranth leaf protein (ALP), eggplant leaf protein (ELP) and fluted pumpkin leaf protein (FLP) were incorporated into freshly prepared orange juice at an effective and inhibitory concentrations of the peptides. The rate of degradation of ascorbic acid was more in the control juice (140.06 to 18.43 mg/mL) when compared with juice containing peptides at both storage conditions (140.08 to 32.32 mg/mL). However, the rate of ascorbic acid reduction during storage (refrigerated and ambient) was least in the juice containing peptide, isolated from ELP when compared with the juice samples that contained peptides isolated from ALP and FLP. After the eighth week of storage, juice that contained FLP peptide had greater amounts of residual total phenolic content (370.53 & 432.33 µg GAE/100 mL), juice that contained ALP peptide retained better ability to scavenge DPPH radicals (52.32 & 66.84%) while juice sample that contained ELP retained more metal chelating activities (44.82 and 51.03%). The results of antidiabetic property showed that juice containing peptide isolated from ALP contained greater amounts of α-amylase inhibitory activity (41.50 and 46.89%) while greater amounts of α-glucosidase inhibitory activities were retained in juice that contained peptide isolated from FLP. The results concluded that orange juice may be considered a veritable vehicle for functional ingredients for improved health. Graphical Abstract