Lectins,trypsin and α-amylase inhibitors in dietary supplements containing <Emphasis Type="Italic">Phaseolus vulgaris</Emphasis>

Some dietary supplements used to control overweight are based on protein concentrates from Phaseolus vulgaris, or kidney bean, known to contain high levels of α-amylase inhibitor, which may reduce the adsorption and prevent the digestion of carbohydrates. These concentrates of kidney bean also contain significant levels of antinutritional factors such as lectins and trypsin inhibitors. In recent years the concentrates of kidney bean have been processed to inactivate lectins and trypsin-inhibitor activity while preserving substantial α-amylase inhibitor activity. The aim of this study was to investigate and to compare the activity of the α-amylase inhibitor in some commercial supplements, and to determine the levels of residual lectins and trypsin inhibitors. The results show that the technological treatment used to reduce the levels of lectins and trypsin inhibitors partially decreases the activity of the amylase inhibitor. This study suggests the need for better standardization of the technological treatment of protein concentrates to ensure both the efficacy and safety of these dietary supplements.     

Inhibition of the in vitro activities of α-amylase, α-glucosidase and pancreatic lipase by yellow field pea (Pisum sativum L.) protein hydrolysates

The aim of this work was to produce yellow field pea protein-derived peptides as inhibitors of α-amylase, α-glucosidase and pancreatic lipase activities. A pea protein concentrate was hydrolysed with alcalase, chymotrypsin, pepsin or trypsin and the hydrolysates separated into different fractions (<1, 1–3, 3–5, 5–10 kDa) by membrane ultrafiltration. Peptide sequence analysis showed that the alcalase hydrolysate had higher levels of di- and tripeptides when compared with the chymotrypsin, pepsin and trypsin hydrolysates. The peptide fractions inhibited α-amylase and α-glucosidase activities at levels that were similar to the unfractionated hydrolysates. The peptides were more active against α-amylase (inhibition at μg level) than α-glucosidase (mg level). In contrast, the fractionated peptides had reduced ability (IC₅₀ >4.2 mg mL⁻¹) when compared with the unfractionated hydrolysate (IC₅₀ <4.2 mg mL⁻¹) to inhibit lipase activity. Enzyme kinetic studies revealed that the peptides reduced α-amylase activity through competitive inhibition. However, inhibition of α-glucosidase activity was non-competitive.     

Major triterpenes,cycloeucalenone and 31-norcyclolaudenone as inhibitors against both α-glucosidase and α-amylase in banana peel

The inhibitory activities of banana peel extract against carbohydrate digestive enzymes were investigated. Cycloeucalenone and 31-norcyclolaudenone were obtained by bioassay-guided fractionation as effective inhibitors of α-glucosidase and α-amylase. The structure–activity relationships of four triterpenes isolated from banana peel, cycloeucalenone, 31-norcyclolaudenone and cycloeucalenol and its isomer were investigated. The IC₅₀ values of cycloeucalenone and 31-norcyclolaudenone against α-glucosidase were 31.83 ± 2.46 μm and 38.85 ± 1.54 μm , respectively, and their IC₅₀ values against α-amylase were 20.33 ± 0.59 μm and 27.63 ± 0.83 μm , respectively. In contrast, cycloeucalenol and its isomer had insufficient inhibitory activity against either enzyme. The primary active sites of cycloeucalenone and 31-norcyclolaudenone are the carbonyl group at C-3 and the double bond in the side chain. Cycloeucalenone induced a parabolic mixed-type inhibition with a K_i value of 73.86 μm in the α-glucosidase inhibitory assay. This study provides new evidence for the potential use of banana peel triterpenes as antidiabetic agents.     

Differential biochemical and kinetic properties of α-amylases from Rhyzopertha dominica (F.) progenies reared on wheat varieties differing in α-amylase inhibitory activity

The present study was accomplished to gain insights into the biochemical and kinetic properties of Rhyzopertha dominica’s α-amylase isoforms (named RdA70, RdA79, and RdA90) expressed in progenies reared in wheat varieties differing in α-amylase inhibitory activity. An inverse relationship was observed between the progenies’ amylase activity and the wheat inhibitory activity. Wheat samples with a high and low infestation (named HI-Borlaug and LI-Villa Juarez, respectively) were chosen to simplify the study. The progenies amylases were isolated by hydrophobic interaction chromatography, while the wheat samples were analyzed in α-amylase inhibitory activity by size exclusion chromatography. The isoforms RdA70 and RdA90 from LI-Villa Juarez progeny showed higher enzyme activities (73.8 and 43.4%, respectively) than those from HI-Borlaug. When the amylase isoforms were tested in susceptibility to inhibition by the inhibitory albumins, those from LI-Villa Juarez were more susceptible than those of the HI-Borlaug. Determination of the kinetic parameters revealed that RdA70 from the HI-Borlaug progeny showed 3.0-fold less starch affinity than that from the LI-Villa Juarez (K_m of 12.3 ± 1.8 versus 4.0 ± 0.3). The rest of the α-amylases did not show the same pattern as RdA70 in the HI-Bourlag as that their starch affinity was further reduced (RdA79 K_m = 23.1 ± 4.3, RdA90 K_m = 17.1 ± 2.9). Estimation of IC₅₀ values confirmed the high sensitivity of the three α-amylases of the LI-Villa Juarez progeny to wheat α-amylase inhibitors. The inhibitor constant K_i was the lowest for RdA70 in the LI-Villa Juarez progeny indicating the inhibitor’ tight binding to that isoenzyme. These results suggest that R. dominica uses RdA70 to bind large amounts of wheat α-amylase inhibitors than RdA79 and RdA90 as a physiological defense mechanism.     

α-Glucosidase and α-amylase inhibitory constituent of Carex baccans: Bio-assay guided isolation and quantification by validated RP-HPLC–DAD

Carex baccans is used extensively as food additive for its medicinal and nutritional properties. Its extract demonstrated significant inhibition of α-glucosidase and α-amylase with IC₅₀ 43.32 ± 1.22 and 562.18 ± 5.98 μg/mL, respectively. A bio-assay guided approach was employed to identify the active constituent(s). Fractionation and purification of the extract led to the isolation of a potent inhibitor, (+)-α-viniferin, and of weak inhibitors smiglasides A and B. (+)-α-Viniferin was quantified in the extract and fractions using HPLC and the method was validated for linearity, limit of detection, limit of quantification, precision, and accuracy. The calibration curve showed good linearity (r² > 0.999) in the range of 7.813–250 μg/mL. The identification of α-glucosidase and α-amylase inhibitory activity in C. baccans supports the possible use of the plant as functional food for the management of diabetes. The validated HPLC method for the study of plant extracts will be useful in future research.     

Effects of extrusion and conventional processing methods on protein and antinutritional factor contents in pea seeds

The effects of high temperature short time (HTST) treatment compared with other conventional processes on protein, phytic acid, condensed tannins, polyphenols, trypsin, chymotrypsin and α-amylase inhibitor activities and haemagglutinating activities in Renata, Solara and Ballet pea seeds were investigated. Ballet cultivar showed highest protein, phytic acid, tannin, polyphenol contents and trypsin and chymotrypsin inhibitory activities. All pea cultivars contained trypsin- and chymotrypsin-inhibiting activity and lectins but only Solara had α-amylase inhibitory activity. Under extrusion conditions (148°C, 25% moisture and 100 rpm) this thermal processing method was the most effective in condensed tannin, trypsin, chymotrypsin, α-amylase inhibitors and haemagglutinating activity reduction, without modifying protein content as occurs by dehulling, soaking and germination treatments. Trypsin and chymotrypsin inhibitors and haemagglutinating activities in peas were more readily abolished by extrusion treatment than was chymotrypsin inhibitory activity.     

α-Glucosidase and α-amylase inhibitors from seed oil: A review of liposoluble substance to treat diabetes

One of the effective managements of diabetes mellitus, in particular, noninsulin-dependent diabetes mellitus, is to retard the absorption of glucose by inhibition of carbohydrate hydrolyzing enzymes, such as α-glucosidase and α-amylase, in the digestive organs. Currently, there is renewed interest in plant-based medicines and functional foods modulating physiological effects in the inhibition of α-glucosidase and α-amylase. Accordingly, inhibitors of α-glucosidase or α-amylase derived from various sources have also been isolated, and majority of phenolic compounds and their effects have been investigated in animals as well. As such, when the presence of α-glucosidase inhibitor in many foodstuffs was screened for, we found that vegetable seed oil also strongly inhibited α-glucosidase and α-amylase. Seed oil is an important source of liposoluble constituents with potential for inhibition of these enzymes, hence can also be used as therapeutic or functional food sources. Therefore, this review is aimed at highlighting the main liposoluble classes of α-glucosidase and α-amylase inhibitors, but it is not intended to be an exhaustive review on the subject.     

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.     

Multiple molecular forms of finger millet subtilisin and amylase inhibitors

Nine varieties of finger millet (Eleusine coracana Gaertn) including a wild form were screened for proteinase and α-amylase inhibitory activities. Subtilisin inhibitory activity was present in all the varieties examined and was highest in the wild form, while the cultivated varieties had more trypsin inhibitory activity. Isoelectric focusing of a 60% ammonium sulphate fraction of the wild form, before and after complexing with subtilisin, showed multiple forms of subtilisin inhibitors one of which was also active against trypsin. Isoforms of finger millet subtilisin inhibitors were isolated from the ammonium sulphate fraction by ion exchange chromatography on DEAE-Sephadex followed by SP-Sephadex chromatography. Copurification of trypsin and α-amylase inhibitory activities with subtilisin inhibitory activity was observed during cation exchange chromatography. PAGE analysis revealed them to be charge isomers with pI in the range 5·5–6·0. SDS–PAGE gave an estimate of 12 000 mol wt for each of them. Finger millet subtilisin inhibitors were more active on bacterial proteinases than on bovine trypsin and chymotrypsin.     

银耳多糖对淀粉消化酶的抑制作用及其机理研究

目的:研究银耳多糖对胰α-淀粉酶和α-葡萄糖苷酶的抑制作用及机制。方法:以干银耳为原料,分别采用碱法提取、酶法脱蛋白和柱层析分离,得到总糖含量为92.45%的银耳多糖（Tremella fuciformis polysaccharide,TP）,采用可见光分光光度法分析了TP对胰α-淀粉酶和α-葡萄糖苷酶的抑制作用,采用荧光光谱法和圆二色谱法表征了TP对该两种酶结构的影响。结果:TP能抑制该两种酶的活性,其对胰α-淀粉酶的抑制作用明显高于α-葡萄糖苷酶,对该两种酶的半抑制浓度（IC₅₀）分别为7.6835和16.9306 mg/mL。TP通过与该两种淀粉消化酶发生相互作用抑制其活性。TP与胰α-淀粉酶相互作用明显,可静态猝灭此酶,改变其二级结构;TP与α-葡萄糖苷酶相互作用微弱,不能改变其二级结构。结论:TP通过与淀粉消化酶发生相互作用抑制其活性。     

Is There Consistency between the Binding Affinity and Inhibitory Potential of Natural Polyphenols as α-amylase Inhibitors?

The inhibitory potential of natural polyphenols for α-amylases has attracted great interests among researchers. The structure–affinity properties of natural polyphenols binding to α-amylase and the structure–activity relationship of dietary polyphenols inhibiting α-amylase were deeply investigated. There is a lack of consistency between the structure-affinity relationship and the structure-activity relationship of natural polyphenols as α-amylase inhibitors. Is it consistent between the binding affinity and inhibitory potential of natural polyphenols as with α-amylase inhibitors? It was found that the consistency between the binding affinity and inhibitory potential of natural polyphenols as with α-amylase inhibitors is not equivocal. For example, there is no consistency between the binding affinity and the inhibitory potential of quercetin and its glycosides as α-amylase inhibitors. However, catechins with higher α-amylase inhibitory potential exhibited higher affinity with α-amylase.     

In vitro evaluation of digestive enzyme inhibition and antioxidant effects of naked oat phenolic acid compound (OPC)

This research was focused on digestive enzyme inhibition and antioxidant properties of naked oat phenolic acid compound (OPC). Free and bound phenolic acid were separated from ethyl acetate fraction, n-butanol fraction and aqueous fraction. The interactions between OPC and main digestive enzymes (α-amylase, α-glucosidase, pepsin and trypsin) were studied. It was shown that the semi-purified bound phenolic acid (semi-purified by AB-8 column) has a competitive alpha-glucosidase inhibitor, while OPC of the organic extract fraction exhibited the characteristics of a mixed inhibitor. Bound phenolic-n-butanol fraction (IC₅₀ = 98.39 ± 0.89 µg mL⁻¹) had the strongest ability to scavenge the 1,1-diphenyl-2-picrylhydrazyl (DPPH). Additionally, the starch hydrolysis degree of n-butanol extraction naked oat phenolic compound was significantly lower than other fractions in vitro. The integrated results suggested that OPC could be considered as potential healthy factor to control postprandial blood glucose, and the mechanism maybe via anti-digestion, antioxidation and interaction with diabetes-related starch.     

Antinutritional factors changes occurring in trifoliate yam (Dioscorea dumetorum) tubers after harvest

Studies were conducted on the changes in antinutritional factors occurring during the storage of Dioscorea dumetorum (cv. Yellow) yam tubers. The tubers were harvested and stored under prevailing tropical ambient conditions (19–28 °C, 60–85% RH) for 0, 2, 5, 7, 14, 21, 28, 42 and 56 days. The samples were evaluated for total phenols, tannins, phytic acid, α-amylase inhibitors, trypsin inhibitors and oxalates. Results showed that, during storage, total phenols and tannin contents decreased by approximately 22–28% after 56 days of harvest, due to the hardening phenomenon and sprouting. Phytate and α-amylase inhibitor levels declined, respectively, from 690–416 mg/100 g and 1013–659 AIU/g, while oxalates and trypsin inhibitor contents increased during the first week of storage (days 0–7) and, after this period, they started to decrease progressively. Since sprouting of most tubers was observed after 28 days of storage, the results suggest that post-harvest hardening and sprouting influence antinutritional composition of D. dumetorum tubers.     

Curcumin as a mild natural α-glucosidase inhibitor: a study on its mechanism in vitro

Curcumin, natural dietary ingredient, is considered as mild effective inhibitors for α-glucosidase to prevent type 2 diabetes. In this work, spectroscopic techniques combined with molecular simulation were used to further understand the inhibition kinetic mechanism of curcumin on α-glucosidase. Curcumin showed a mild inhibition effect (IC₅₀ =20.54 ± 1.02 mg/ml) for α-glucosidases through a competitive inhibition mechanism, and it led to fluorescence quenching as well as energy transfer by binding behaviour (average binding distance, r₀ = 2.43 nm). Hydrogen bonds and steric hindrance were the main interactions between curcumin and the activity site of α-glucosidases, as revealed by molecular docking. Circular dichroism spectroscopy results also indicate that curcumin affected the denaturation temperature of α-glucosidases, which dropped from 74 °C to 68 °C, resulting in inhibition. The findings can contribute to a better understanding of the development and application of curcumin in functional dietary food.     

Effects of carboxymethylation,hydroxypropylation and dual-enzyme hydrolysis combination with heating on in vitro hypoglycaemic properties of coconut cake dietary fibres

Effects of carboxymethylation, hydroxypropylation and dual-enzyme hydrolysis combined with heating on in vitro hypoglycaemic properties of coconut cake dietary fibre (CCDF) were studied. Results showed that all the three modification methods could effectively improve (P < 0.05) the glucose-adsorption ability (GAA), glucose dialysis retardation index (GDRI), α-glucosidase and α-amylase inhibition activity of CCDF. The highest GAA (4.45–4.93 mm  g⁻¹), GDRI (85.09–86.94% mm  g⁻¹) and α-glucosidase inhibition activity (16.39–19.37%) were found on CCDFs modified by hydroxypropylation and carboxymethylation, attributed to the increased soluble dietary fibre content, viscosity and water retention and swelling capacity. Moreover, CCDF treated by enzymatic hydrolysis combined with heating demonstrated the highest α-amylase inhibition activity (53.95%), attributed to the high specific surface area, more porous surface structure and formation of fibre–amylase complex proved by fluorescence spectroscopy. These results suggest that the modified CCDFs could be used as low-calorie functional ingredients in food or other industries.     

Antioxidant and type II diabetes related enzyme inhibition properties of methanolic extract of an underutilized food legume,Canavalia ensiformis (L.) DC: Effect of traditional processing methods

The methanolic extract of Canavalia ensiformis (L.) DC (Jack bean) seed, an underutilized food legume collected from India was analyzed for antioxidant and health relevant functional properties. The raw seeds contained total free phenolic content of 12.98 ± 1.63 g catechin equivalent/100 g extract DM. The raw seed extract exhibited ferric reducing/antioxidant power (FRAP, 1218 mmol Fe[II]/mg extract), inhibition of β-carotene degradation (49.81%), radical scavenging activity against DPPH (56.78%) and superoxide (35.89%). In addition, 77.56% of α-amylase and 75.45% of α-glucosidase enzyme inhibition characteristics were found under in vitro starch digestion bioassay. Sprouting + oil-frying caused an apparent increase on the total free phenolic content with significant improvement on antioxidant and free-radical scavenging capacity, while soaking + cooking as well as open-pan roasting treatments showed diminishing effects. Inhibition of α-amylase and α-glucosidase enzyme activities were declined to 22.69 and 42.69%, respectively during sprouting + oil-frying treatment is more desirable for the dietary management of type II diabetic patients.     

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.     

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.     

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.     

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.