Gamma/alpha‐zein hydrolysates as oral delivery vehicles: Enhanced physicochemical stability and in vitro bioaccessibility of curcumin

In this study, we aimed to evaluate the potential of the γ‐zein hydrolysate (γ‐ZH) as a new delivery system for hydrophobic bioactive molecules such as curcumin (Cur). γ‐ZH‐Cur complexes (γ‐ZH‐Cur) with a particle size of 50–60 nm were successfully formed via the hydrogen bonding and hydrophobic interactions. Compared to α‐ZH, the complexation of Cur in γ‐ZH showed a better improvement in the water solubility and physicochemical stability of Cur and showed sustained release and greater potential for absorption of Cur. The differences in the loading capability, the physicochemical storage and the bioaccessibility of Cur between γ‐ZH and α‐ZH may be associated with the differences in the amino acid composition and typical sequence of peptides. These results indicate that γ‐ZH has a better ability to serve as a novel delivery for the hydrophobic bioactive molecules compared to α‐ZH.     

Purification and physicochemical characterization of ovine β‐lactoglobulin and α‐lactalbumin

Ovine whey proteins were fractionated and studied by using different analytical techniques. Anion‐exchange chromatography and reversed‐phase high‐performance liquid chromatography (HPLC) showed the presence of two fractions of β‐lactoglobulin but only one of α‐lactalbumin. Gel permeation and sodium dodecyl sulfate (SDS)‐polyacrylamide gel electrophoresis allowed the calculation of the apparent molecular mass of each component, while HPLC coupled to electrospray ionisation‐mass spectrometry (ESI‐MS) technique, giving the exact molecular masses, demonstrated the presence of two variants A and B of ovine β‐lactoglobulin. Amino acid compositions of the two variants of β‐lactoglobulin differed only in their His and Tyr contents. Circular dichroism spectroscopy profiles showed pH conformation changes of each component. The thermograms of the different whey protein components showed a higher heat resistance of β‐lactoglobulin A compared to β‐lactoglobulin B at pH 2, and indicated high instability of ovine α‐lactalbumin at this pH.     

Inhibitory activities of kaempferol,galangin, carnosic acid and polydatin against glycation and α‐amylase and α‐glucosidase enzymes

The activities of four natural phenolics, kaempferol, galangin, carnosic acid and polydatin in scavenging free radicals, inhibiting advanced glycation end‐product (AGE) formation, α‐amylase and α‐glucosidase and trapping methylglyoxal (MGO), were evaluated in this study. Carnosic acid and galangin had the highest activity in scavenging free radicals. Kaempferol and galangin had the greatest activity in preventing bovine serum albumin (BSA) against glycation and reducing glycated proteins. Polydatin had the greatest performance in trapping MGO to reduce glycation reaction. However, there was no significant difference for kaempferol, galangin and carnosic acid in inhibiting AGE formation by BSA‐MGO reaction. Kaempferol, galangin and carnosic acid were the competitive inhibitors for α‐amylase, while kaempferol and carnosic acid were noncompetitive inhibitors for α‐glucosidase. However, polydatin showed as a mixed noncompetitive inhibitor for both α‐amylase and α‐glucosidase. The results indicated that the four natural phenolics have potential in inhibiting AGE production and the digestive enzymatic activity with different mechanisms.     

Chemical Constituents of Gold‐red Apple and Their α‐Glucosidase Inhibitory Activities

Ten compounds were isolated and purified from the peels of gold‐red apple (Malus domestica) for the 1st time. The identified compounds are 3β, 20β‐dihydroxyursan‐28‐oic acid (1), 2α‐hydroxyoleanolic acid (2), euscaphic acid (3), 3‐O‐p‐coumaroyl tormentic acid (4), ursolic acid (5), 2α‐hydroxyursolic acid (6), oleanolic acid (7), betulinic acid (8), linolic acid (9), and α‐linolenic acid (10). Their structures were determined by interpreting their nuclear magnetic resonance and mass spectrometry (MS) spectra, and by comparison with literature data. Compound 1 is new, and compound 2 is herein reported for the 1st time for the genus Malus. α‐Glucosidase inhibition assay revealed 6 of the triterpenoid isolates as remarkable α‐glucosidase inhibitors, with betulinic acid showing the strongest inhibition (IC₅₀ = 15.19 μM). Ultra‐performance liquid chromatography‐electrospray ionization MS analysis of the fruit peels, pomace, flesh, and juice revealed that the peels and pomace contained high levels of triterpenes, suggesting that wastes from the fruit juice industry could serve as rich sources of bioactive triterpenes.     

Screening grape seeds recovered from winemaking by‐products as sources of reducing agents and mammalian α‐glucosidase and α‐amylase inhibitors

Grape seeds collected from vinification of various grape varieties were extracted by supercritical CO₂ for oil recovery. The defatted residues thus obtained were considered as a re‐utilisable co‐product and assessed for phenolic content, reducing capacity and inhibitory activities against mammalian α‐amylase and α‐glucosidase enzymes. Supercritical CO₂ treatment led to higher recovery of anthocyanins. Reducing capacity of phenolic extracts reached up to ~2200 mmolFe(II) kg^?1, much higher than that of various natural phenolic sources. The anthocyanin‐rich extracts showed the highest inhibitory effectiveness towards α‐glucosidase (I₅₀ value equal to ~40 μg gallic acid equivalents (GAE)/mL ~ half than acarbose). Inhibitory effectiveness towards α‐amylase activity was similar among grape varieties, with I₅₀ values comparable to that of acarbose and correlated with proanthocyanidin contents. These results could pave the way for an efficient processing of grapes, including cascade processes, namely: winemaking, oil extraction from recovered grape seeds and phenolic extraction from defatted grape seeds as potential cost‐effective nutraceuticals.     

In vitro inhibitory effects of cranberry bean (Phaseolus vulgaris L.) extracts on aldose reductase, α‐glucosidase and α‐amylase

The in vitro inhibitory activities of different seed extracts prepared from cranberry bean mutant SA‐05 and its wild‐type variety Hwachia against aldose reductase, α‐glucosidase and α‐amylase were examined. The results indicated that the polyphenolics‐rich extracts obtained using 800 g kg^?1 methanol and 500 g kg^?1 ethanol demonstrated inhibitory activities against aldose reductase (IC₅₀ of 0.36–0.46 mg mL^?1) and α‐glucosidase (IC₅₀ of 1.32–1.94 mg mL^?1). The 500 g kg^?1 ethanol extracts also showed α‐amylase inhibitory activities (IC₅₀ of 70.11–80.22 μg mL^?1). Subsequent extracts, prepared further with NaCl and H₂O from precipitates of 800 g kg^?1 methanol or 500 g kg^?1 ethanol extracts, exhibited potent α‐amylase inhibitory activities (IC₅₀ of 17.68–38.68 μg mL^?1). A combination of 500 g kg^?1 ethanol extraction plus a subsequent H₂O extraction produced highest polyphenolics and α‐amylase inhibitors. The SA‐05 α‐amylase inhibitor extracts showed greater inhibitory activities than that of Hwachia. Thus, cranberry bean mutant SA‐05 is an advantageous choice for producing anti‐hyperglycaemic compounds.     

Characterization of the Supermolecular Structure of Polydatin/6‐O‐α‐Maltosyl‐β‐cyclodextrin Inclusion Complex

Polydatin is the main bioactive ingredient in many medicinal plants, such as Hu‐zhang (Polygonum cuspidatum), with many bioactivities. However, its poor aqueous solubility restricts its application in functional food. In this work, 6‐O‐α‐Maltosyl‐β‐cyclodextrin (Malt‐β‐CD), a new kind of β‐CD derivative was used to enhance the aqueous solubility and stability of polydatin by forming the inclusion complex. The phase solubility study showed that polydatin and Malt‐β‐CD could form the complex with the stoichiometric ratio of 1:1. The supermolecular structure of the polydatin/Malt‐β‐CD complex was characterized by ultraviolet–visible spectroscopy (UV), Fourier transform infrared spectroscopy (FT‐IR), X‐ray diffractometry (XRD), thermogravimetric/differential scanning calorimetry (TG/DSC), and proton nuclear magnetic resonance (¹H‐NMR) spectroscopy. The changes of the characteristic spectral and thermal properties of polydatin suggested that polydatin could entrap inside the cavity of Malt‐β‐CD. Furthermore, to reasonably understand the complexation mode, the supermolecular structure of polydatin/Malt‐β‐CD inclusion complex was postulated by a molecular docking method based on Autodock 4.2.3. It was clearly observed that the ring B of polydatin oriented toward the narrow rim of Malt‐β‐CD with ring A and glucosyl group practically exposed to the wide rim by hydrogen bonding, which was in a good agreement with the spectral data.     

Alterations of the Profiles of Iso‐α‐Acids During Beer Ageing,Marked Instability of Trans‐Iso‐α‐Acids and Implications for Beer Bitterness Consistency in Relation to Tetrahydroiso‐α‐Acids

Age‐induced decomposition of iso‐α‐acids, the main bittering principles of beer, determines the consistency of the beer bitter taste. In this study, the profiles of iso‐α‐acids in selected high‐quality top‐fermented and lager beers were monitored by quantitative high‐performance liquid chromatography at various time intervals during ageing. The degradation of the iso‐α‐acids as a function of time is represented by the ratio, in percentage, of the sum of the concentrations of trans‐isocohumulone and trans‐isohumulone to the sum of the concentrations of cis‐isocohumulone and cis‐isohumulone. This parameter is relevant with respect to the evaluation of bitterness deterioration in aged beers. Trans‐iso‐α‐acids having a shelf half‐life of less than one year proved to be significantly less stable than cis‐iso‐α‐acids, but it appears feasible to counteract degradation if a suitable beer matrix is available. The fate of the trans‐iso‐α‐acids in particular adversely affects beer bitterness consistency. In addition to using hop products containing low amounts of trans‐iso‐α‐acids, brewers may profit of the remarkable stability of tetrahydroiso‐α‐acids, even on prolonged storage, for the production of consistently bitter beers.     

α‐Glucosidase and α‐amylase inhibitory activities of phloroglucinal derivatives from edible marine brown alga,Ecklonia cava

BACKGROUND: Diabetes mellitus (DM) is a chronic metabolic disorder characterized by defects in insulin secretion and action, which can lead to damaged blood vessels and nerves. With respect to effective therapeutic approaches to treatment of DM, much effort has being made to investigate potential inhibitors against α‐glucosidase and α‐amylase from natural products. The edible marine brown alga Ecklonia cava has been reported to possess various interesting bioactivities, which are studied here. RESULTS: In this study, five phloroglucinal derivatives were isolated from Ecklonia cava: fucodiphloroethol G ( 1 ), dieckol ( 2 ), 6,6′‐bieckol ( 3 ), 7‐phloroeckol ( 4 ) and phlorofucofuroeckol A ( 5 ); compounds 1, 3 and 4 were obtained from this genus for the first time and with higher yield. The structural elucidation of these derivatives was completely assigned by comprehensive analysis of nuclear magnetic spectral data. The anti‐diabetic activities of these derivatives were also assessed using an enzymatic inhibitory assay against rat intestinal α‐glucosidase and porcine pancreatic α‐amylase. Most of these phlorotannins showed significant inhibitory activities in a dose‐dependent manner, responding to both enzymes, especially compound 2 , with the lowest IC₅₀ values at 10.8 µmol L^?1 (α‐glucosidase) and 124.9 µmol L^?1 (α‐amylase), respectively. Further study of compound 2 revealed a non‐competitive inhibitory activity against α‐glucosidase using Lineweaver‐Burk plots. CONCLUSION: These results suggested that Ecklonia cava can be used for nutritious, nutraceutical and functional foods in diabetes as well as for related symptoms. Copyright © 2009 Society of Chemical Industry     

Anti‐acetylcholinesterase,antidiabetic, anti‐inflammatory,antityrosinase and antixanthine oxidase activities of Moroccan propolis

Biological properties of Moroccan propolis have been scarcely studied. In the present work, the total phenols and flavonoids from 21 samples of propolis collected in different places of Morocco or 3 supplied in the market were determined, as well as the in vitro capacity for inhibiting the activities of acetylcholinesterase, α‐glucosidase, α‐amylase, lipoxygenase, tyrosinase, xanthine oxidase and hyaluronidase. The results showed that samples 1 (region Fez‐Boulemane, Sefrou city) (IC₅₀ = 0.065, 0.006, 0.020, 0.050, 0.014 mg mL^?1) and 23 (marketed) (IC₅₀ = 0.018, 0.002, 0.046, 0.037, 0.008 mg mL^?1) had the best in vitro capacity for inhibiting the α‐amylase, α‐glucosidase, lipoxygenase, tyrosinase and xanthine oxidase activities, respectively. A negative correlation between IC₅₀ values and concentration of phenols, flavones and flavanones was found. These activities corresponded to the generally higher amounts of phenols and flavonoids. In the same region, propolis samples have dissimilar phenol content and enzyme inhibitory activities.     

Thermal modifications of structure and codenaturation of α‐lactalbumin and β‐lactoglobulin induce changes of solubility and susceptibility to proteases

Study of heat denaturation of major whey proteins (β‐lactoglobulin or α‐lactalbumin) either in separated purified forms, or in forms present in fresh industrial whey or in recomposed mixture respecting whey proportions, indicated significant differences in their denaturation depending on pH, temperature of heating, presence or absence of other co‐denaturation partner, and of existence of a previous thermal pretreatment (industrial whey). α‐Lactalbumin, usually resistant to tryptic hydrolysis, aggregated after heating at ⪈85°C. After its denaturation, α‐lactalbumin was susceptible to tryptic hydrolysis probably because of exposure of its previously hidden tryptic cleavage sites (Lys‐X and Arg‐X bonds). Heating over 85°C of β‐lactoglobulin increased its aggregation and exposure of its peptic cleavage sites. The co‐denaturation of α‐lactalbumin with β‐lactoglobulin increased their aggregation and resulted in complete exposure of β‐lactoglobulin peptic cleavage sites and partial unveiling of α‐lactalbumin tryptic cleavage sites. The exposure of α‐lactalbumin tryptic cleavage sites was slightly enhanced when the α‐lactalbumin/β‐lactoglobulin mixture was heated at pH 7.5. Co‐denaturation of fresh whey by heating at 95°C and pH 4.5 and above produced aggregates stabilized mostly by covalent disulfide bonds easily reduced by β‐mercaptoethanol. The aggregates stabilized by covalent bonds other than disulfide arose from a same thermal treatment but performed at pH 3.5. Thermal treatment of whey at pH 7.5 considerably enhanced tryptic and peptic hydrolysis of both major proteins.