Solanum macrocarpon (eggplant) leaf protein isolate (ELI) was hydrolyzed using four different enzymes to produce hydrolysates from alcalase (AH), chymotrypsin (CH) pepsin (PH) and trypsin (TH). CH had an overall stronger antioxidant property and was separated using ultrafiltration membranes into <1, 1–3 and 3–5 kDa peptide fractions. Gel-permeation chromatography confirmed conversion of the ELI (average of 22 kDa) into protein hydrolysates that contained smaller peptides (<6 kDa). A total of 23 peptides consisting of tri and tetrapeptides were identified from the CH, which is a wider spectrum when compared to seven for AH and four each for TH and PH. CH exhibited stronger scavenging activities against DPPH and hydroxyl radicals. CH and TH exhibited the strongest inhibitions against angiotensin-converting enzyme. In contrast, AH was the strongest inhibitor of α-amylase while AH and PH had strong inhibitory activities against α-glucosidase when compared with other hydrolysates. Ultrafiltration fractionation produced peptides that were stronger (p < 0.05) scavengers of DPPH, and hydroxyl radicals, in addition to better metal-chelating and enzyme inhibition agents. The study concluded that the eggplant protein hydrolysates and the UF fractions may find applications in tackling oxidative stress-related diseases and conditions involving excessive activities of the metabolic enzymes.

Isoelectric precipitation was used to produce protein isolates (>90% protein contents) from three edible vegetable leaves. Amaranth (ALI), eggplant (ELI) and fluted pumpkin (FLI) leaf protein were isolated to study their conformational structures. Intrinsic fluorescence indicated a loose structural conformation for ELI at all the pH values, whereas FLI and ALI had more compact structures at pH 3.0 and pH 9.0. The surface hydrophobicity showed a greater distribution of hydrophobic amino acid groups of the protein isolates at the basic than the acidic regions. The SDS-PAGE results showed that the leaf isolates had similar polypeptide bonds characterized by 20, 25, 40 and 200 kDa and some distinct bands above 200 kDa. The ELI formed emulsions with significantly (p < .05) smallest oil droplet sizes (<3.3 µm) when compared to FLI and ALI. However, foaming capacity was mostly pH-dependent with significantly (p < .05) higher values at pH 7.0 and 9.0. The leaf protein isolates may be considered as potential functional food ingredients.

The need to feed the increasing world population with high quality protein and the enormous post-harvest losses of okra fruits necessitated the research on okra seeds in this study. Whole flour (WF) of matured okra seed was processed to obtain defatted flour (DF), protein concentrate (PC) and protein isolate (PI), followed by hydrolysis of the protein isolate by three different proteases; pepsin (PHp), pancreatin (PHc) and trypsin (PH_T) to produce hydrolysates. The okra seed flours, proteins and the hydrolysates were analyzed for changes in the functional groups using Fourier, Transform Infrared (FTIR), amino acid composition, solubility profile and some functional properties. The FTIR results showed the presence of N-H stretching, C=O stretching, C=N stretching N-H bending and C-N stretching in the samples. Protein hydrolysate had higher essential amino acids (51.32–53.01%) than unhydrolysed samples (36.31–37.99%). PI and WF had the highest water absorption and swelling capacities respectively. The solubility profiles of the samples were minimal at pH 2–4 and then increased after the isoelectric point. The PC was more soluble than PI between pH 2–8. The foaming properties of the samples was least in the absence of salt but high in the presence of 0.5 M sodium chloride. The emulsion capacity of the samples was least in the presence of 1.0 M NaCl. The in-vitro protein digestibility results showed that okra seed protein hydrolysates were more digestible (83.26–86.08%) than unhydrolyzed proteins (36.48–80.90%). The results of the antioxidant properties showed that PHp and PH_T exhibited better radical scavenging and metal chelating activities respectively than the other samples. The study concluded that okra seed proteins and hydrolysates demonstrated potentials as ingredients in functional food preparation and this may be considered as a strategy to reducing the post-harvest losses of okra fruit and subsequently feeding the world with quality proteins. Graphical

Hydrolysates were produced using Alcalase (AH), chymotrypsin (CH), pepsin (PH), and trypsin (TH), and also fluted pumpkin leaf protein isolate (FLI) as a substrate. AH had the lowest degree of hydrolysis (16.37%) but exhibited overall superior antioxidant and enzyme inhibitory properties....

Optimization of the yield, total phenolic content (TPC), and total antioxidant activities (TAA) of polyphenol concentrates extracted from Solanum macrocarpon leaves was studied using response surface methodology. The process variables investigated included extraction temperature (30, 50, and 70°C), extraction time (2, 4, and 6 h), and dried leaf powder : water ratio (1 : 10, 1 : 20, and 1 : 30 w/v). Box–Behnken design resulted in 15 experimental runs. The results showed the following optimum extraction conditions: temperature, 49.05°C; extraction time, 243 min; leaf powder : water ratio, 1 : 22 w/v. The optimized extraction conditions gave polyphenol concentrate yield, TPC, and TAA values of 24.94%, 421.09 mg GAE/g, and 23.81 mg AAE/g, respectively. Results of the in vitro antioxidant activities of the polyphenol concentrate showed 2, 2-diphenyl-2-picrylhydrazyl hydrate, metal chelating ability, and ferric reducing ability values of 76.78%, 80.22%, and 56.46 mg AAE/g, respectively. The study concludes that the experimental values compared closely with the predicted values, which indicates suitability of the model employed for polyphenol extraction optimization from dried S. macrocarpon leaves.