Antioxidant activity and stability of α-tocopherol,resveratrol and epigallocatechin-3-gallate in mixture and complexation with bovine serum albumin

Ligand-binding proteins were proposed as ideal carriers for the co-encapsulation of bioactive compounds. Multiple compounds co-encapsulated in food formulation may give rise to different effects on bioactivity and stability. The protein effect on the interplay between bioactive compounds was investigated for selecting suitable co-encapsulation strategy. α-Tocopherol, resveratrol and epigallocatechin-3-gallate (EGCG), as model compounds, interacted with bovine serum albumin (BSA) to form tri-ligand complexes when added in the sequence. For ferric-reducing antioxidant power, the mixtures of α-tocopherol and resveratrol,α-tocopherol and EGCG, resveratrol and EGCG were respectively additive, antagonistic and synergistic, while their ternary mixture were antagonistic. For ABTS+ scavenging capacity, all pairs were antagonistic. BSA improved FRAP of α-tocopherol, resveratrol and EGCG mixture but decreased their ABTS inhibition. Although structural stability and antioxidant activity of resveratrol decreased when alone interacted with BSA, they were improved when α-tocopherol and EGCG were co-presented. Mixing the antioxidants improved their stability and the complexation with BSA can further stabilise them. BSA could thus be a suitable carrier for co-encapsulation/protection of α-tocopherol, resveratrol and EGCG in functional foods.     

In vitro screening of phenolic compounds, potential inhibition against α-amylase and α-glucosidase of culinary herbs in Thailand

Herbs that are commonly used in Thai dishes were selected for evaluation in order to determine their phenolic compounds, antioxidant activity, and in vitro potential inhibition against α-amylase and α-glucosidase. The total phenolic content ranged from 2.89 to 75.26 mg GAE/g dw. The three aqueous herb extracts with the highest total phenolic content were yellow-berried nightshade (Solanum xanthocarpum), holy basil (Ocimum sanctum) and acacia (Acacia pennata). The antioxidant activity was expressed as percent inhibition of DPPH, ranging from a high of 85% in bitter gourd (Monordica charantia) to a low of 0% in garlic (Allium sativum) and shallot (Allium cepa). A high correlation (r = 0.70, p < 0.05) was observed between total phenolic content and antioxidant activity for the herb extracts in the Solanaceae family while, an insignificant high and negatively correlation (r = −1.00, p > 0.05) for the herb extracts in the Cucurbitaceae and Umbelliferae families was observed. All of the herbs had caffeic content, varying from 0.00 to 23.93 mg/g dw. Peppermint (Mentha canalenisa), galangal (Languas galangal) and holy basil (O. sanctum) had a significant p-coumaric acid content. The first and second obtained principal component represented 60% of the total variation. The potential inhibition against α-amylase for the herbs extracts ranged from 0% to 58%, while the highest percentage was observed in the acacia (A. pennata) extract. The potential inhibition against α-glucosidase varied from 7% to 100%. A high correlation (r = 0.68, p < 0.05) was observed between α-amylase inhibition and caffeic acid content for aqueous extracts in the Alliaceae, Cucurbitaceae, and Leguminosae families, while a high correlation (r = 0.49, p < 0.05) was observed between α-glucosidase inhibition and total phenolic content for the aqueous extracts of all herbs. Therefore, specific culinary herbs showed to have a potential use for dietary management during the early stages of hyperglycaemia.     

Extraction of phenolic compounds from grapes and their pomace using β-cyclodextrin

Use of aqueous cyclodextrins (CD) for recovery of selected bioactive phenolic compounds from grapes and their pomace was evaluated. When α, β and γ forms of CD were compared, β-CD was the most effective in recovering stilbenes, flavonols, and flavan-3-ols from grape pomace. The maximum quantified phenolics were obtained from the powder and the slurry of grape pomace when extracted with 2.5% (w/v) aqueous β-CD solutions at 60 °C for 12–24 h. With β-CD, total quantified phenolics obtained from the dry powder were 123 mg/100 g (DW) while from the slurry, they were 35.8 mg/100 g (FW). Incorporation of β-CD to grape mash prior to pressing for juice enhanced the recovery of phenolics in juice. Incorporation of β-CD was more effective in recovering flavan-3-ols than flavonols. Aqueous CD can effectively be used in recovering phenolics from by-products of fruit processing and therefore for functional foods and nutraceutical applications.     

Isolation and identification of phenolic compounds from the seeds of Perilla frutescens (L.) and their inhibitory activities against α-glucosidase and aldose reductase

Five phenolic compounds were isolated from the seeds of Perilla (Perilla frutescens L.) using gradient solvent fractionation, silica gel column chromatography, and preparative high-performance liquid chromatography (HPLC). Their chemical structures were identified as caffeic acid-3-O-glucoside (1), rosmarinic acid-3-O-glucoside (2), rosmarinic acid (3), luteolin (4), and apigenin (5) using NMR spectroscopy and HPLC-ESI/MS analysis. Among them, luteolin (4) inhibited α-glucosidase (EC 3.2.1.20) with IC(50) value of 45.4μM. The inhibition kinetic analysed by Dixon plot indicate that luteolin is a noncompetitive inhibitor, and the inhibition constant K(I) was calculated at 45.0μM. Moreover, rosmarinic acid (3) and luteolin (4) inhibited recombinant human aldose reductase (EC 1.1.1.21) with IC(50) values of 11.2 and 0.6μM, respectively. Notably, the inhibition kinetic of luteolin (4) follows a hyperbolic dependence on aldose reductase inhibition by Dixon plot. Thus, inhibition kinetic indicates that luteolin (4) is a mixed-type inhibitor.     

Biological activity of rice extract and the inhibition potential of rice extract,rice volatile compounds and their combination against α-glucosidase, α-amylase and tyrosinase

Rice is produced for consumption and traditional medicine. Rice is also used as an ingredient in cosmetic products. In this study, the author investigated the biological activity and inhibition potential against α-glucosidase, α-amylase and tyrosinase activity of rice extract (black rice [BR], red rice [RR] and white rice [WR]), rice volatile compounds, rice extract combined with volatile compounds, rice extract combined with standard inhibitors and volatile compounds combined with standard inhibitors. The results revealed that the free-radical scavenging capacity of rice extract is related to the phenolic content and flavonoids. BR showed the highest potential to inhibit α-glucosidase and α-amylase activity, whereas WR showed the highest potential to inhibit tyrosinase activity. Among rice volatile compounds, vanillin and vanillyl alcohol had the highest inhibition potential against α-glucosidase and α-amylase, respectively, whereas guaiacol had the highest inhibitory activity against tyrosinase. Molecular docking supported by the high binding efficiency was also obtained from vanillin and guaiacol when located at the active site of these enzymes. The combination of RR with acarbose (AB) had the highest inhibition potential and showed a synergic effect on both α-glucosidase and α-amylase. Interestingly, the combination of rice extract (BR, RR and WR) and vanillin and vanillyl alcohol had a synergic effect on α-amylase. Moreover, the combination of WR and vanillyl alcohol had the highest inhibition potential and showed a synergic effect on tyrosinase, whereas rice volatile compounds had a synergic effect on tyrosinase obtained from 2-pentylfuran/kojic acid (KA), vanillin/KA and vanillyl alcohol/KA.     

Structural,morphological and rheological characterisation of bovine serum albumin–cress seed gum complex coacervate

The interactions between the bovine serum albumin (BSA) and cress seed gum (CSG) were investigated by structural, morphological and rheological characterisation as a function of pH level (7.0–2.0) and biopolymers’ concentrations (BSA, 0.1%, 0.5% and 1%, w/w and CSG, 0.01%, 0.05% and 0.1%, w/w). The results showed that turbidity, zeta potential and coacervate yield values had correlations with the initial number of biopolymers, which are influenced by the level of the positive and negative charges of BSA and CSG. Furthermore, the optimal complexation conditions in terms of pH, CSG-BSA content and yield were 3.5%, 0.05–0.1% and 61.17% respectively. Rheological properties revealed the formation of a weakly gel-like structure with a shear-thinning behaviour. X-ray diffraction (XRD) and scanning electron microscopy (SEM) authenticated an amorphous and branch-like network structure in the coacervate phase respectively. These results reflect that CSG-BSA complex coacervate could be an appropriate biopolymer carrier for susceptible and bioactive compounds.     

Biochemical characterisation of α-amylase inhibitors from Achyranthes aspera and their interactions with digestive amylases of coleopteran and lepidopteran insects

BACKGROUND: Starchy seeds are an important food and a source of dietary ingredients in many countries. However, they suffer from extensive predation by bruchids (weevils) and other pests. α‐Amylase inhibitors are attractive candidates for the control of seed weevils, as these insects are highly dependent on starch as an energy source. RESULTS: A proteinaceous α‐amylase inhibitor from the seeds of Achyranthes aspera was identified, purified and characterised. In electrophoretic analysis, two prominent amylase inhibitor activity bands (AI1 and AI2) were detected. The inhibitor was purified 9.99‐fold with 1206.95 total amylase inhibitor units mg^?1 protein. The molecular weight of the purified inhibitor was around 6 kDa. The isolated α‐amylase inhibitor was found to be resistant to heat and proteolysis. Feeding analysis of Callosobruchus maculatus larvae on a diet containing seed powder of A. aspera revealed that survival of the larvae was severely affected, with the highest mortality rate occurring on the fifth day of feeding. The isolated inhibitor inhibited the majority of amylase isoforms of C. maculatus, Tribolium confusum and Helicoverpa armigera in electrophoretic analysis and solution assays. CONCLUSION: The information obtained in the present investigation could be useful for a genetic engineering approach that would make seeds resistant to storage pest infestations. Copyright © 2011 Society of Chemical Industry     

Interaction of milk α- and β-caseins with tea polyphenols

The interaction of α- and β-caseins with tea polyphenols (+)-catechin (C), (−)-epicatechin (EC), (−)-epigallocatechin (EGC) and (−)-epigallocatechin gallate (EGCG) was examined at a molecular level, using FTIR, UV–visible, CD and fluorescence spectroscopic methods as well as molecular modelling. The polyphenol binding mode, the binding constant and the effects of polyphenol complexation on casein stability and conformation were determined. Structural analysis showed that polyphenols bind casein via both hydrophilic and hydrophobic interactions with overall binding constants of K_C–α-cas = 1.8 (±0.8) × 10³ M⁻¹, K_EC–α-cas = 1.8 (±0.6) × 10³ M⁻¹, K_EGC–α-cas = 2.4 (±1.1) × 10³ M⁻¹ and K_{EGCG–α-cas} = 7.4 (±0.4) × 10³ M⁻¹, K_C–β-cas = 2.9 (±0.3) × 10³ M⁻¹, K_EC–β-cas = 2.5 (±0.6) × 10³ M⁻¹, K_EGC–β-cas = 3.5 (±0.7) × 10³ M⁻¹ and K_{EGCG–β-cas} = 1.59 (±0.2) × 10⁴ M⁻¹. The number of polyphenol bound per protein molecule (n) was 1.1 (C), 0.9 (EC), 1.1 (EGC), 1.5 (EGCG) for α-casien and 1.0 (C), 1.0 (EC), 1.1 (EGC) and 1.5 (EGCG) for β-casein. Structural modelling showed the participation of several amino acid residues in polyphenol–protein complexation with extended H-bonding network. Casein conformation was altered by polyphenol with a major reduction of α-helix and β-sheet and increase of random coil and turn structure suggesting further protein unfolding. These data can be used to explain the mechanism by which the antioxidant activity of tea compounds is affected by the addition of milk.     

Equilibrium and non-equilibrium complexes between bovine serum albumin and dextran sulfate—I. Complexing conditions and composition of non-equilibrium complexes

The complexing between bovine serum albumin (BSA) and dextran sulfate (DS) with ionic strengths of 0.01–0.1 was studied at pH 2.7–5.6. At pHs above the BSA isoelectric point (IEP), BSA sorption by DS is reversible and non-cooperative. The swing to cooperative BSA sorption is observed over the pH range 5.6–5.0. At pHs below the BSA IEP, BSA sorption becomes irreversible. When the sorption is irreversible the insoluble complex composition (regardless of the method of macroreagent mixing) depends on the initial ratio between protein and polysaccharide concentration. The macroreagent concentration ratio allowing 100% yield of insoluble complexes corresponds to equality of molar concentrations of BSA cationic groups and DS sulfate groups. Precipitation of non-equilibrium complexes takes place even in the case of low protein content (about 150 monosaccharide units per BSA molecule). Possible reasons for stabilization of non-equilibrium states of the studied complexes are considered.     

Activity and stability enhancement of α-amylase treated with sub- and supercritical carbon dioxide

Various physical, chemical and genetic approaches have been applied in order to enhance enzyme stability and activity. In this study, the aim was to investigate the capability of sub- and supercritical carbon dioxide to alter the stability and activity of α-amylase as an alternative technique. The effects of operational parameters such as pressure (50-300 bar), temperature (28-80 °C), CO? flow (2-10 g min?1) and time (60-180 min) were evaluated in regard to the activity and stability of fungal based α-amylase from Aspergillus oryzea. The activity of untreated enzyme was determined as 17,726 μmol/ml/min. While both sub- and supercritical conditions enhanced the activity, the increase in flow rate had an adverse effect and the activity was decreased by 28.9% at a flow rate of 10 g min?1 under supercritical conditions. Nuclear magnetic resonance (NMR) spectra of untreated enzyme and treated samples exhibiting the lowest and the highest activities were almost identical except for the chemical shifts observed at the lowest activity sample from 4.0 to 4.4 ppm which were assigned to protons of hydrogen-bonded groups. Optimum conditions were determined as 240 bar, 41 °C, 4 g min?1 CO? flow and 150 min of process duration yielding 67.7% (29,728 μmol/ml/min) higher activity than the untreated enzyme providing fundamental basis for enzymatic applications.     

Effect of ascorbic acid and protein concentration on the molecular weight profile of bovine serum albumin and β-lactoglobulin by γ-irradiation

The effects of ascorbic acid and protein concentration on the molecular weight size distribution of BSA and β-lactoglobulin were examined after irradiation of proteins at various doses. Gamma-irradiation of protein solutions caused disruption of the ordered structure of protein molecules resulting in degradation, cross-linking, and aggregation of the polypeptide chains. SDS–PAGE and gel permeation chromatography study showed that ascorbic acid protected the aggregation and degradation of proteins by scavenging oxygen radicals produced by irradiation and the effect of irradiation on protein conformation was more significant at lower concentrations of proteins.     

Variability and relationship among Mixolab and Falling Number evaluation based on influence of fungal α-amylase addition

BACKGROUND: In bread‐making technology, α‐amylase activity is routinely measured with a Falling Number device to predict wheat flour quality. The aim of this study was to determine the possibility of using Mixolab parameters to assess the Falling Number (FN) index. The effects of different doses of fungal α‐amylase addition on the Mixolab characteristics and FN index values were investigated. RESULTS: Principal component analysis was performed in order to illustrate the relationships between the Mixolab parameters and the FN index. To highlight the linear combination between the FN index values and the Mixolab parameters used to evaluate starch pasting properties (C3, C4, C5 and point differences C34 and C54), a multivariate prediction model was developed. Greatest precision (R = 0.728) was obtained for the linear regression FN = f(C4, C54) model. This model was tested on a different sample set than the one on which it was built. A high correlation was obtained between predictive model and measured FN index values (r = 0.896, P = 0.01). CONCLUSION: The model provides a framework to predict the evolution of the FN index, which is predicted by the torque for cooking stability (C4) and the difference between points C5 and C4 (C54). The obtained results suggested that the Mixolab device could be a reliable instrument for evaluation of the FN index values. Copyright © 2012 Society of Chemical Industry     

Reverse micellar extraction of bovine serum albumin – A comparison between the effects of gemini surfactant and its corresponding monomeric surfactant

Gemini surfactant displayed distinct advantages over monomeric surfactant in the liquid–liquid reverse micellar extraction process. First, less amount of gemini surfactant than monomeric surfactant was needed for transferring almost complete bovine serum albumin (BSA) into organic phase from aqueous phase. Second, the loading capacity of gemini surfactant reverse micelle phase was much higher than that of the corresponding monomeric surfactant reverse micelle. Third, efficient backward extraction (75–92%) of BSA could be effected in a wide pH range from 4 to 9 with gemini surfactant reverse micelle while a pH of ca. 4.3 is prerequisite to the recovery of BSA from monomeric surfactant reverse micelle. So far, the reports about the effect of surfactant structure on protein extraction have been limited. This study indicates the important role of the spacer of gemini surfactant in protein extraction process and may provide more knowledge on how to optimise surfactant structure.     

Potential interactions among phenolic compounds and probiotics for mutual boosting of their health-promoting properties and food functionalities – A review

Several foods are rich sources of phenolic compounds (PC) and their beneficial effects on human health may be increased through the action of probiotics. Additionally, probiotics may use PC as substrates, increasing their survival and functionality. This review presents available studies on the effects of PC on probiotics, including their physiological functionalities, interactions and capability of surviving during exposure to gastrointestinal conditions and when incorporated into food matrices. Studies have shown that PC can improve the adhesion capacity and survival of probiotics during exposure to conditions that mimic the gastrointestinal tract. There is strong evidence that PC can modulate the composition of the gut microbiota in hosts, improving a variety of biochemical markers and risk factors for chronic diseases. Available literature also indicates that metabolites of PC formed by intestinal microorganisms, including probiotics, exert a variety of benefits on host health. These metabolites are typically more active than parental dietary PC. The presence of PC commonly enhances probiotic survival in different foods. Finally, further clinical studies need to be developed to confirm in vitro and experimental findings concerning the beneficial interactions among different PC and probiotics.