Activated effect of lignin on α-amylase

This paper reports a new kind of activator of α-amylase, lignin, which can greatly increase α-amylase activity. The promoted ratio of lignin is even much higher than that of chloride ion, the traditional activator of α-amylase. Further experimental results reveal that lignin may interact with α-amylase to form a 1:1 complex with a binding constant of 4.47 × 10⁵ M⁻¹. The binding is spontaneous and lignin/α-amylase complex formation is an exothermal reaction. Hydrogen bonding plays a key role and non-radiation energy transfers from α-amylase to lignin in the binding process. Lignin, combining with α-amylase, conforms to a first-order exponential decay function. The formation of the lignin/α-amylase complex results in the reduction of α-helical content from 57.7% to 53.9%, the increase of the polarity around tryptophan residues, the decrease of the hydrophobicity, and the enlargement of protein granule volume. This work will give a deeper insight into lignin as a kind of dietary fibre, known as an important food functional factor. Furthermore, it also contributes to the exploration of an activator of α-amylase, used in the food industry.     

Effects of rendering and α-tocopherol addition on the oxidative stability of horse fat

Food Science and Biotechnology - Oxidative stability of horse fat rendered at 70 °C, − 0.1 MPa under vacuum and 110 °C, 0.1 MPa from horse...     

Retention effect of human saliva on aroma release and respective contribution of salivary mucin and α-amylase

As great differences were observed in the amount of α-amylase in human saliva, there is a need to better understand the effect of this protein alone or in mixture with mucin on aroma compound partitioning. We report the respective role of mucin and α-amylase on the air/liquid partition coefficients of two series of 5 methyl-ketones and 5 ethyl-esters. We confirm that mucin affects the release of aroma compounds and, for the first time, we demonstrate the ability of α-amylase to decrease the release of aroma compounds. For both proteins, we report the involvement of hydrophobic effects. Interestingly, no cumulative effect was observed when both proteins were mixed together in solution. We hypothesize that protein–protein interactions occur between the two proteins and decrease the total number of available binding sites for aroma compounds. The effect of human saliva is also investigated and compared to that of artificial salivas. In the presence of human saliva the release of ketones is lower than in water and slightly higher than in the presence of artificial saliva composed of α-amylase and/or mucin. Esters are more affected by the presence of human saliva than ketones. This observation is due to the presence of an esterase activity in saliva, which activity increases with the hydrophobicity of esters. The difference observed in aroma release between artificial and human salivas could be explained by the presence of other salivary proteins in human saliva.     

The α-amylase and α-glucosidase inhibitory effects of Irish seaweed extracts

To date, numerous studies have reported on the antidiabetic properties of various plant extracts through inhibition of carbohydrate-hydrolysing enzymes. The objective of this research was to evaluate extracts of seaweeds for α-amylase and α-glucosidase inhibitory effects. Cold water and ethanol extracts of 15 seaweeds were initially screened and from this, five brown seaweed species were chosen. The cold water and ethanol extracts of Ascophyllum nodosum had the strongest α-amylase inhibitory effect with IC₅₀ values of 53.6 and 44.7 μg/ml, respectively. Moreover, the extracts of Fucus vesiculosus Linnaeus were found to be potent inhibitors of α-glucosidase with IC₅₀ values of 0.32 and 0.49 μg/ml. The observed effects were associated with the phenolic content and antioxidant activity of the extracts, and the concentrations used were below cytotoxic levels. Overall, our findings suggest that brown seaweed extracts may limit the release of simple sugars from the gut and thereby alleviate postprandial hyperglycaemia.     

Effect of additives on mesophilic α-amylase and its application in the desizing of cotton fabrics

An investigation was carried out on thermal stability of α-amylase. The influence of various additives (calcium acetate, sodium lactate, L-histidine, and water-soluble chitosan) on the stability of α-amylase was studied. Results showed the inactivation behavior of α-amylase with or without additives all followed the first-order kinetics. All additives (Ca2+, sodium lactate, L-histidine, and water-soluble chitosan) displayed good stabilizing effect on α-amylase lower than 80 °C, and only water-soluble chitosan had an efficient stabilizing effect on α-amylase when the treatment temperature exceeds 80 °C. All additives improved the catalytic activity of α-amylase at 70–90 °C, and the appearance of water-soluble chitosan increased the catalytic activity of α-amylase at 90 °C sharply. A desizing ratio of 68.42% was obtained by treating the cotton fabrics in the buffer solution at 100 °C without α-amylase. To obtain a desizing ratio exceed 95% when fabrics were treated at 100 °C for 10 min, the addition of water-soluble chitosan saves 2/3 α-amylase dosage. Moreover, water-soluble chitosan showed a further improvement in desizing effect than the additive of calcium acetate.     

Preparation and characterization of α-tocopherol nanocapsules based on gum Arabic-stabilized nanoemulsions

Food Science and Biotechnology - The preparation of water dispersed α-tocopherol nanocapsules through solvent-displacement technique using gum Arabic (GA) as natural stabilizing and...     

Changes in structure and aroma release from starch–aroma systems upon α-amylase addition

The influence of starch hydrolysis by α-amylase addition on structural properties and aroma release from starch–aroma systems was studied. A food model system composed of aqueous tapioca starch dispersion (4 g dry starch/100 g dispersion) and one aroma compound (menthone) was investigated. Structure breakdown and related changes in starch fraction (amylose) were measured by rheology and iodine-binding. Menthone release from the aroma-starch system in the headspace was followed by proton transfer reaction-mass spectrometry (PTR-MS) upon starch hydrolysis. A slightly higher viscosity was found for the starch–menthone system compared to the starch system without menthone upon α-amylase addition. One could hypothesise that menthone acts as a kind of nucleation agent for inducing structure build-up of starch segments, hindering starch degradation. An extensive aroma release from aroma–starch systems upon α-amylase addition was expected, but, instead, just a slight volatile increase was found after a starch hydrolysis time of 60 min. It is suggested that aroma release is the result of several superimposed effects ranging from viscosity effects to interactions between aroma compounds and starch degradation products.     

Metabolite profiling and inhibitory properties of leaf extracts of Ficus benjamina towards α-glucosidase and α-amylase

The use of antioxidant-rich medicinal plants having the potential to reduce oxidative stress and postprandial hyperglycemic pressure is one of the most promising option for the management of diabetes. This study presents information on metabolite profiling and in vitro anti-diabetic effects of leaf extracts of Ficus benjamina. The DPPH (2, 2-diphenyl-1-picrylhydrazyl radicals) assay was performed to determine the in vitro antioxidant potential of the plant extracts. The anti-diabetic effects were investigated by evaluating inhibitory properties of F. benjamina leaf extracts towards carbohydrate hydrolyzing enzymes, i.e., α-glucosidase and α-amylase, whereas ¹H NMR and UHPLC-QTOF-MS/MS analytical methods were employed for metabolite profiling of F. benjamina leaf extracts. Among 40, 60, 80, and 100% ethanolic leaf extracts of F. benjamina, 80% ethanolic extract exhibited the highest antioxidant activity based upon its DPPH radical scavenging ability (IC₅₀ value: 63.71 ± 2.66 µg/mL). The 80% ethanolic leaf extract of F. benjamina also proved to be the most efficient α-glucosidase and α-amylase inhibitor with IC₅₀ values of 9.65 ± 1.04 µg/mL and 13.08 ± 1.06 µg/mL, respectively; these values were even better than acarbose with α-glucosidase inhibition activity (IC₅₀ = 116.01 ± 3.83 µg/mL) and α-amylase inhibition activity (IC₅₀ = 152.66 ± 7.32 µg/mL). Moreover, a total of 31 metabolites were identified in F. benjamina leaf extract, which may have the potential to contribute to its antioxidant and inhibitory properties against carbohydrate hydrolyzing enzymes. The findings of this study depict F. benjamina leaf extracts as a promising α-glucosidase and α-amylase inhibitor, and therefore, can be utilized for the development of anti-diabetic functional diets/nutra-pharmaceuticals.     

α-Glucosidase and α-amylase inhibitory activities of guava leaves

The 75% ethanol extract from guava (Psidium guajava Linn.) leaves was extracted further, in turn, with CH₂Cl₂, EtOAc and n-BuOH to afford four fractions, CH₂Cl₂-soluble, EtOAc-soluble, n-BuOH-soluble and residual extract fractions. Both the n-BuOH-soluble and EtOAc-soluble fractions showed high inhibitory activity against α-glucosidase and α-amylase. Seven pure flavonoid compounds, quercetin (1), kaempferol (2), guaijaverin (3), avicularin (4), myricetin (5), hyperin (6) and apigenin (7), were isolated (using enzyme assay-guide fractionation method) from the n-BuOH-soluble and EtOAc-soluble fractions. The structures of these pure compounds were determined on the basis of MS and NMR data and the activities of these compounds were evaluated. Compounds 1, 2 and 5 showed high inhibitory activities, with IC₅₀ values of 3.5 mM, 5.2 mM and 3.0 mM against sucrase, with IC₅₀ values of 4.8 mM, 5.6 mM and 4.1 mM against maltase and with IC₅₀ values of 4.8 mM, 5.3 mM and 4.3 mM against α-amylase, respectively. We found that myricetin showed the most powerful activity among these compounds with a 70% inhibition against sucrase at a concentration of 1.5 mg/ml. The hydroxyl group at the 3-position on the A-ring and a number of hydroxyl groups attached to the C-ring played important roles in the inhibition activity. There was an obvious synergistic effect (the mixing action of two compounds) against α-glucosidase, but against α-amylase this was not found. This is the first study of the active compositions of guava leaves and the biological activity of the active compositions against α-glucosidase and α-amylase.     

Inhibitory activities of extracts from Cleistocalyx operculatus flower buds on pancreatic lipase and α-amylase

In this work, we investigated the inhibitory activities of aqueous extract (Eaq), 30, 60, and 95?% ethanol extracts (E₃et, E₆et, and E₉et), petroleum ether extract (Epe), ethyl acetate extract (Eae), and 2′,4′-dihydroxy-6′-methoxy-3′,5′-dimethylchalcone (DMC) from Cleistocalyx operculatus flower buds on pancreatic lipase and α-amylase, which were closely related to body weight and obesity. The inhibition effect of various extracts was determined by the Lineweaver–Burk plots. The results showed that the IC₅₀ values of DMC, Epe, Eae, and E₉et against pancreatic lipase were 101.5?μM, 38.65, 76.62, and 109.76?μg/ml, respectively, which were much lower than that of E₃et and E₆et. Eaq, E₃et, E₆et, and DMC strongly inhibiting the pancreatic α-amylase, with IC₅₀ values of 73.10, 165.93, 231.23?μg/ml, and 69.35?μM, respectively. Furthermore, the kinetic analysis suggested that the inhibition mode of crude extract against pancreatic lipase was noncompetitive, while that against pancreatic α-amylase was competitive. The content of DMC and total polyphenols in each extract were determined by HPLC and spectrophotometric method, respectively. It was interestingly found that the DMC content had profound influence on pancreatic lipase activity, and the total polyphenols content significantly affected the pancreatic α-amylase activity. The findings in this work suggested that extracts from C. operculatus flower buds possess potent inhibitory activity against pancreatic lipase and α-amylase, and provided some new ideas for the prevention and treatment for obesity.     

Activity of diastase α-amylase immobilized on polyanilines (PANIs)

Starch hydrolysing enzyme α-amylase (EC 3.2.1.1) was immobilized by physical adsorption and covalent binding onto chemically synthesised polymer, polyanilines (PANIs) in two different forms, emeraldine salt and emeraldine base powder. The immobilization efficiency was affected by the pH of the immobilization medium, contact time and amount of enzyme. The kinetic parameters, reusability and storage stability of the enzyme were studied under free and immobilized condition at optimum pH and temperature. The immobilized enzyme showed enhanced storage stability over a period of 6 months, while free enzyme in solution lost all of its activity within a period of 8 days. Reusability of the enzyme was improved by immobilization. The K_m values for starch hydrolysis were found to be high for the immobilized enzymes.     

Interaction of phenolic compounds with bovine serum albumin (BSA) and α-amylase and their relationship to astringency perception

The ability of grape seed extracts to bind to bovine serum albumin (BSA) and α-amylase was studied by fluorescence quenching of protein intrinsic fluorescence and nephelometry. The influence of grape seed ripeness on astringency was also evaluated. From the spectra obtained, the modified Sterm-Volmer (K(app)) and the bimolecular quenching constants were calculated. Results showed that grape seed extracts had good affinity for proteins. The association strength of tannin-protein interactions varied with changes in tannin structure associated with the degree of ripeness affecting the binding/quenching process. In all cases studied, higher values of K(app) were obtained in samples at harvest which have greater ability to bind to proteins than have samples at post-veraison time. Nephelometric assays show the same trend as do fluorescence quenching studies. A possible explanation for this is that, as seeds ripen, their tannins increase in molecular mass, which relates to an increase in hydrophobicity of the molecules, and this increases protein affinity. However, that is contrary to the reported decrease in astringency of grape seeds during maturity. This indicates that tannin-protein interactions are not the only explanation for the complex sensations of astringency of grape seeds.     

The inhibitory effects of ethanol extracts from sorghum,foxtail millet and proso millet on α-glucosidase and α-amylase activities

Cereal crops have recently experienced increased interest due to their potential health benefits. It has been suggested that the intake of whole grain foods is beneficial to the prevention and management of diabetes mellitus. In this study, we investigated the inhibitory effect of 70% EtOH extracts from different cultivars of sorghum, foxtail millet and proso millet on α-glucosidase and α-amylase. Among the six sorghum cultivars, Mongdang-susu(SS-1), Me-susu(SS-2), Susongsaengi-susu(SS-3) and Sikyung-susu(SS-4) extracts exhibited higher inhibitory activities against α-glucosidase (IC₅₀ = 1.1–1.4 μg/ml) than acarbose, reference inhibitor (IC₅₀ = 2.1 μg/ml). In addition, these extracts strongly inhibited degradation of starch by pancreatic and salivary α-amylase, whereas extracts from foxtail and proso millets exhibited no visible or detectible inhibitory effect on α-amylase or on α-glucosidase activity. These in vitro studies indicate the potential of sorghum in the development of effective anti-diabetic agents.     

Identification and characterization of novel α-amylase and α-glucosidase inhibitory peptides from camel whey proteins

This study explores the inhibitory properties of camel whey protein hydrolysates (CWPH) toward α-amylase (AAM) and α-glucosidase (AG). A general full factorial design (3 × 3) was applied to study the effect of temperature (30, 37, and 45°C), time (120, 240, and 360 min), and enzyme (pepsin) concentration (E%; 0.5, 1, and 2%). The results showed that maximum degree of hydrolysis was obtained when hydrolysis was carried out at higher temperature (45°C; P < 0.05), compared with lower temperatures of 30 and 37°C. Electrophoretic pattern displays degradation of all protein bands upon hydrolysis by pepsin at various hydrolysis conditions applied. All the 27 CWPH generated showed significant AAM and AG inhibitory potential as indicated by their lower IC₅₀ values (mg/mL) compared with intact whey proteins. In total 196 peptides were identified from selected hydrolysates and 15 potential peptides (PepSite score > 0.8; http://pepsite2.russelllab.org/) were explored via in silico approach. Novel peptides PAGNFLMNGLMHR, PAVACCLPPLPCHM, MLPLMLPFTMGY, and PAGNFLPPVAAAPVM were identified as potential inhibitors for both AAM and AG due to their high number of binding sites and highest binding probability toward the target enzymes. CCGM and MFE, as well as FCCLGPVPP were identified as AG and AAM inhibitory peptides, respectively. This is the first study that reports novel AG and AAM inhibitory peptides from camel whey proteins. The future direction for this research involves synthesis of these potential AG and AAM inhibitory peptides in a pure form and investigate their antidiabetic properties in the in vitro, as well as in vivo models. Thus, CWPH can be considered for potential applications in glycaemic regulation.     

Chemical fractionation of caseins by differential precipitation: influence of pH,calcium addition,protein concentration and temperature on the depletion in α- and β-caseins

The impact of pH, calcium and casein concentrations, and temperature on the efficiency of the differential precipitation of caseins by calcium affinity was investigated, using native phosphocaseinate as starting material. We adapted one of the most recent methods for the separation of caseins that is based on the addition of calcium at alkaline pH. Increasing the pH to 11 disturbed the micellar structure by enhancing electrostatic repulsion of caseins, leading to a marked viscosity increase and a significant particle size decrease, indicating casein micelle disruption. This pH-driven increase in negative charges enhanced the affinity of individual caseins for calcium, proportionally to the number of phosphate groups carried by each casein. The addition of calcium first led to a progressive increase in the proportion of precipitated caseins, before reaching a plateau. Hence, an optimal calcium/casein molar ratio of about 40 was evidenced to optimise casein precipitation (and fractionation), leading to significant depletion of α-casein (around 80%) and, in a lesser extent, β-casein (around 65%) and κ-casein (around 55%). This method led to relative proportions of caseins significantly differing from the starting material: 31% α-casein, 45% β-casein and 24% κ-casein.     

Extractability and evaluation of α-galactosides of sucrose in leguminous seeds

The levels of sucrose and α-galactosides of sucrose in a range of leguminous seeds extracted by various procedures and analysed by the gel-permeation technique are reported. Cowpeas contained the highest levels of α-galactosides, dry weight basis, the lowest levels being recorded in chickpeas. Levels in lupins are almost comparable with soybeans and intermediate quantities have been measured in adzuki beans. All the legumes examined contained varying amounts of α-galactoside-hydrolysing enzyme (α-galactosidase EC 3.2.1.22) and the defatting process has no effect on its activity. No hydrolysis of these oligomers due to the extraction technique has been observed, except in one procedure. Conditions of cultivation may have been responsible for anomalies in the values of these oligomers observed by various investigators within the same variety and species of a leguminous seed.     

Inhibitory effect of Zanthoxylum bungeanum maxim. and Capsicum annuum L. on the activities of pancreatic lipase and α-amylase

Zanthoxylum bungeanum maxim. (ZBM) and Capsicum annuum L. (CAL) are popular condiments in China. In this study, the inhibition of pancreatic lipase and α-amylase by ZBM and CAL extracts, as well as catechin, rutin, hydroxy-α-sanshool (from ZBM extract) and capsaicin (from CAL extract), was determined. The half maximal inhibitory concentration (IC₅₀) values of ZBM extract, CAL extract, rutin, hydroxy-α-sanshool and capsaicin against pancreatic lipase were 82.1, 533.5, 583.8, 565.7 and 62.4 μg mL⁻¹, respectively, while that against α-amylase were 125.6, 1167.2, 213.2195.6 and 163.2 μg mL⁻¹, respectively. Catechin had no detectible inhibition on the two enzymes even at 4 mg mL⁻¹. The combination of hydroxy-α-sanshool and capsaicin against the two enzymes showed similar inhibition trends to that of ZBM and CAL extracts (synergism at low concentrations but antagonism at high concentrations), suggesting the two compounds were closely associated with the functions of the crude extracts. The results obtained from the in vitro digestion were similar but with a lower inhibition rate. Kinetic studies revealed that ZBM extract, hydroxy-α-sanshool and capsaicin showed mixed-type inhibition for pancreatic lipase and α-amylase. Molecular modelling suggested capsaicin had a higher affinity to the two enzymes, with glide scores of −8.18 and −7.87 kcal mol⁻¹, respectively.     

Extraction optimisation,antioxidant activity and inhibition on α-amylase and pancreatic lipase of polyphenols from the seeds of Syzygium cumini

The objectives of this study were to determine the optimal extraction conditions of polyphenols from Syzygium cumini seeds by response surface methodology and investigate their antioxidant activity and inhibition on α-amylase and pancreatic lipase. As results, the optimal extraction conditions in the ultrasonic extraction process which maximised total polyphenols content, minimised the IC₅₀ values of α-amylase and pancreatic lipase were determined as follows: extraction time 60 min, ethanol concentration 63% and solvent/solid ratio 44 mL g⁻¹. The main phenolic compounds in partially purified fraction of Syzygium cumini seeds were catechin, epicatechin, kaempferol, gallic, 5-caffeoylquinic, caffeic and ferulic acids. In addition, the partially purified fraction inhibited 87.66 ± 5.55 and 86.61 ± 3.15% of α-amylase and pancreatic lipase, respectively. The results suggested that Syzygium cumini seeds could be explored as a natural antioxidant and could be used as a source of highly antidiabetic and anti-obesity bioactive compounds.     

Inhibitory properties of polyphenols in Malus “Winter Red” crabapple fruit on α-glucosidase and α-amylase using improved methods

To explore the inhibitory activity of polyphenols on α-glucosidase and α-amylase, 16 polyphenols were isolated, identified, and quantified in an edible Malus “Winter Red” crabapple fruit. The limitations of two traditional methods for α-glucosidase and α-amylase activity assay in vitro were assayed. An improved method based on an HPLC assay for α-glucosidase and a colorimetric method coupled with a custom-made mini-column for α-amylase were established. Compared with positive controls, acarbose and miglito, most polyphenols, especially the four aglycones (cyanidin, quercetin, phloretin, and 3-hydroxyphloretin) showed higher inhibition rates on α-glucosidase. None of the polyphenols showed higher inhibition rates on α-amylase than acarbose, but most, especially the four aglycones, showed higher inhibition rates on α-amylase than miglito. The Malus Winter Red fruit has great potential for postprandial blood glucose management as a potential diet therapy for diabetic patients.