Understanding Antidiabetic Potential of Oligosaccharides from Red Alga Dulse Devaleraea inkyuleei Xylan by Investigating α-Amylase and α-Glucosidase Inhibition.

In this study, the α-glucosidase (maltase-glucoamylase: MGAM) and α-amylase inhibitory properties elicited by xylooligosaccharides (XOSs) prepared from dulse xylan were analysed as a potential mechanism to control postprandial hyperglycaemia for type-2 diabetes prevention and treatment. Xylan was purified from red alga dulse powder and used for enzymatic hydrolysis using Sucrase X to produce XOSs. Fractionation of XOSs produced xylobiose (X2), ß-(1→3)-xylosyl xylobiose (DX3), xylotriose (X3), ß-(1→3)-xylosyl-xylotriose (DX4), and a dulse XOS mixture with n ≥ 4 xylose units (DXM). The different fractions exhibited moderate MGAM (IC50 = 11.41-23.44 mg/mL) and α-amylase (IC50 = 18.07-53.04 mg/mL) inhibitory activity, which was lower than that of acarbose. Kinetics studies revealed that XOSs bound to the active site of carbohydrate digestive enzymes, limiting access to the substrate by competitive inhibition. A molecular docking analysis of XOSs with MGAM and α-amylase clearly showed moderate strength of interactions, both hydrogen bonds and non-bonded contacts, at the active site of the enzymes. Overall, XOSs from dulse could prevent postprandial hyperglycaemia as functional food by a usual and continuous consumption.

Protein hydrolysates of Moringa oleifera seed: Antioxidant and antihyperglycaemic potential as ingredient for the management of type-2 diabetes.

New plant proteins with high nutritional quality and biological properties are actively searched worldwide. Moringa oleifera seed protein isolate was prepared from defatted flour and hydrolyzed using four proteases namely trypsin, pepsin, Alcalase, and thermolysin. Then, antioxidant activity and cellular glucose uptake properties of the hydrolysates were assessed. A high degree of hydrolysis was obtained for hydrolysate prepared using trypsin (60.07%), followed by pepsin (57.14%), Alcalase (50.68%), and thermolysin (45.45%). Thermolysin hydrolysate was the most antioxidant efficient (IC50 0.15 and 0.74 mg/mL for 2,2'-azino-bis(acide 3-ethylbenzothiazoline-6-sulfonique) diammonium salt (ABTS) and 2,2-Diphenyl-1-picrylhydrazyl (DPPH) scavenging activity, respectively). Trypsin hydrolysate stimulated high glucose uptake by yeast cells (12.34-35.28%). In the absence of insulin, Alcalase hydrolysate was the most efficient for glucose uptake by the muscle, with the rate ranging from 22.03% to 29.93% after 30 min, then from 29.55% to 34.6% after 60 min. The four hydrolysates improved glucose uptake by the muscle in the presence of insulin with the rate ranging from 46.88% to 58.03% after 30 min, and from 50% to 58.18% after 60 min. Therefore, Moringa oleifera seed proteins could be used to prepare peptides as components of functional foods for the management of type-2 diabetes.

Characterisation of Bioactive Peptides from Red Alga Gracilariopsis chorda.

In this study, we studied the bioactive peptides produced by thermolysin hydrolysis of a water-soluble protein (WSP) from the red alga Gracilariopsis chorda, whose major components are phycobiliproteins and Ribulose-1,5-bisphosphate carboxylase-oxygenase (RuBisCo). The results showed that WSP hydrolysate exhibited significantly higher ACE inhibitory activity (92% inhibition) compared to DPP-IV inhibitory activity and DPPH scavenging activity. The phycobiliproteins and RuBisCo of G. chorda contain a high proportion of hydrophobic (31.0-46.5%) and aromatic (5.1-46.5%) amino acid residues, which was considered suitable for the formation of peptides with strong ACE inhibitory activity. Therefore, we searched for peptides with strong ACE inhibitory activity and identified two novel peptides (IDHY and LVVER). Then, their interaction with human ACE was evaluated by molecular docking, and IDHY was found to be a promising inhibitor. In silico analysis was then performed on the structural factors affecting ACE inhibitory peptide release, using the predicted 3D structures of phycobiliproteins and RuBisCo. The results showed that most of the ACE inhibitory peptides are located in the highly solvent accessible α-helix. Therefore, it was suggested that G. chorda is a good source of bioactive peptides, especially ACE-inhibitory peptides.

Effect of heat treatment on the structure, functional properties and composition of Moringa oleifera seed proteins.

Knowledge on how food processing conditions and protein composition can modulate individual or food matrix protein functionality is crucial for designing new protein ingredients. In this regard, we investigated how heat treatment and protein composition influence physicochemical and functional properties of Moringa oleifera seed protein isolate. Results showed that changes in processing temperature induced modifications in the conformation affecting the hydrophobic core of proteins. Protein isolate was more soluble at room temperature whereas prolamin fraction presented high solubility at 70 °C. Glutelin showed higher emulsifying properties at all temperatures. Protein composition also significantly affected physicochemical and functional properties of protein isolate. Increasing soluble glutelin enhanced solubility while increasing albumin, globulin and glutelin decreased hydrophobicity of the isolate. Likewise, increasing soluble globulin improved emulsifying capacity, and emulsion stability of the isolate was negatively affected by increase in albumin and glutelin. These findings could enhance application of Moringa oleifera protein in food formulations.

Influence of pH and temperature on the physicochemical and functional properties of Bambara bean protein isolate.

Bambara bean is a rich low-cost protein source and a functional ingredient in the food industry. We investigated the effects of temperature and different pH on the physicochemical and functional properties of Bambara bean protein isolate. Vicilin was the major protein of Bambara bean as revealed by SDS PAGE analysis. The emulsifying capacity of protein isolate was highest at 80 °C, pH 9 while emulsion stability was highest at pH 4. Generally, increase in temperature decreased protein solubility at pH 4 and 7, while increase was observed at pH 9 and 100 °C. The hydrophobicity of isolate was highest at pH 4 and lowest at pH 9, regardless of temperature. Protein isolate possessed highly compact ß-sheet and α-helix secondary structures in proportions greater than 75% (at pH 9 and 50 °C). Increase in temperature generally promoted protein rearrangement and partial unfolding. Protein secondary structure and surface hydrophobicity can predict food functionality, directly affecting protein behavior during formulation and long-term storage. This study clearly demonstrated the potential of exploiting pulse protein isolates as nutritional and functional ingredients through temperature and pH control.

Investigation on antioxidant, angiotensin converting enzyme and dipeptidyl peptidase IV inhibitory activity of Bambara bean protein hydrolysates.

Protein isolate was hydrolysed by Alcalase, thermolysin and trypsin. BBPH produced by Alcalase showed highest angiotensin-converting enzyme (ACE) inhibitory properties (IC50: 52 µg/mL). Hydrolysates produced by Alcalase and thermolysin exhibited similar dipeptidyl peptidase-IV (DPP-IV) inhibitory activity (IC50: 1.73 mg/mL), while low inhibitory activity was observed for hydrolysate produced by trypsin. BBPH also showed protective effect against oxidative stress with significant 2,2-diphenyl-1-picrylhydrazyl radical scavenging and ferrous chelating activity. Bioactive peptides of BBPH produced by thermolysin showed better resistance to simulated gastrointestinal digestion (SGID), while the DPP-IV and ACE inhibitory properties were significantly reduced. Molecular weight distribution showed significant reduction in peptides of the molecular weight range 200-400 Da in BBPH produced by Alcalase, after SGID. LC-ESI-TOF-MS and in silico analysis showed the presence of potential peptides with both ACE and DPP-IV inhibitory properties in BBPH produced by thermolysin.

Production and characterization of cowpea protein hydrolysate with optimum nitrogen solubility by enzymatic hydrolysis using pepsin.

BACKGROUND: Cowpea is a source of low-cost and good nutritional quality protein for utilization in food formulations in replacement of animal proteins. Therefore it is necessary that cowpea protein exhibits good functionality, particularly protein solubility which affects the other functional properties. The objective of this study was to produce cowpea protein hydrolysate exhibiting optimum solubility by the adequate combination of hydrolysis parameters, namely time, solid/liquid ratio (SLR) and enzyme/substrate ratio (ESR), and to determine its functional properties and molecular characteristics. RESULTS: A Box-Behnken experimental design was used for the experiments, and a second-order polynomial to model the effects of hydrolysis time, SLR and ESR on the degree of hydrolysis and nitrogen solubility index. The optimum hydrolysis conditions of time 208.61 min, SLR 1/15 (w/w) and ESR 2.25% (w/w) yielded a nitrogen solubility of 75.71%. Protein breakdown and the peptide profile following enzymatic hydrolysis were evaluated by sodium dodecyl sulfate polyacrylamide gel electrophoresis and size exclusion chromatography. Cowpea protein hydrolysate showed higher oil absorption capacity, emulsifying activity and foaming ability compared with the concentrate. CONCLUSION: The solubility of cowpea protein hydrolysate was adequately optimized by response surface methodology, and the hydrolysate showed adequate functionality for use in food. © 2016 Society of Chemical Industry.

Optimising functional properties during preparation of cowpea protein concentrate.

Response surface methodology (RSM) was used for modelisation and optimisation of protein extraction parameters in order to obtain a protein concentrate with high functional properties. A central composite rotatable design of experiments was used to investigate the effects of two factors, namely pH and NaCl concentration, on six responses: water solubility index (WSI), water absorption capacity (WAC), oil holding capacity (OHC), emulsifying activity (EA), emulsifying stability (ES) and foam ability (FA). The results of analysis of variance (ANOVA) and correlation showed that the second-order polynomial model was appropriate to fit experimental data. The optimum condition was: pH 8.43 and NaCl concentration 0.25M, and under this condition WSI was ⩾17.20%, WAC⩾383.62%, OHC⩾1.75g/g, EA⩾0.15, ES⩾19.76min and FA⩾66.30%. The suitability of the model employed was confirmed by the agreement between the experimental and predicted values for functional properties.

Functional properties of acetylated and succinylated cowpea protein concentrate and effect of enzymatic hydrolysis on solubility.

The present study was undertaken to improve functional properties of cowpea protein concentrate by acylation and partial hydrolysis with pepsin. The acylated concentrate showed significant improvement in protein solubility and water solubility index, at neutral pH. In addition, acylation increased fat absorption capacity compared with the untreated concentrate, and the maximum was obtained at 0.75 g succinic anhydride/g concentrate. Acetylation at concentrations of 0.25-0.50 g/g led to the higher emulsifying activity, and a markedly improvement in emulsifying stability was observed at 1.0 g anhydride/g concentrate. Foaming activity increased following acylation, particularly at 0.25 and 1.00 g/g succinic anhydride/g concentrate, while foam stability decreased. At pH 3.5, protein solubility of the acylated concentrates was low ( < 8%). Partial hydrolysis of cowpea protein concentrate with pepsin increased protein solubility at the isoelectric and neutral pH.