α-Glucosidase Inhibitors from Glycyrrhiza uralensis Fisch.

Aim To screen for α-glucosidase inhibitor from Glyeyrrhiza uralensis Fisch.. Methods Glycyrrhizic acid, glycyrrhetinic acid, flavonoids of glycyrrhiza, alkaloids of glycyrrhiza, and glycyrrhiza polysaccharides were isolated from the root of Glycyrrhiza uralensis Fisch. respectively. Three compounds were isolated from the flavonoids of glycyrrhiza as guided by the α-glucosidase inhibitory test in vitro. Moreover, the characteristics of inhibitory kinetics of glycyrol and glycyrrhetinic acid were investi- gated. Results The flavonoids of glycyrrhiza and glycyrrhetinic acid had the strongest α-glucosidase inhibitory activity. Glycyrol,β-sitosterol and liquifitin were isolated and identified. Glycyrol was a fast- binding, reversible, noncompetitive α-glucosidase inhibitor, showing IC50 at 0.26 μg·mL^-1 Glycyrrhetinic acid was a fast-binding, irreversible α-glucosidase inhibitor, showing IC50 at 102.4 μg·mL^-1. Conclusion Glycyrol is an effective α-glucosidase inhibitor.

Effects of α-glucosidase Inhibitors on the Function of Mulberry Leaf Extract as an Additive in Feedstuff

The mulberry juice contains high concentrations of α-glucosidase inhibitors that affect glycometabolism and cause diarrhea in animals, thereby affecting the de-velopment and application of mulberry （Morus alba L.） as feedstuff resources. ln this study, the effects of mulberry leaf extract with and without removal of mulberry juice on starch metabolism were analyzed and compared. The results showed that mul-berry leaf extract with removal of mulberry juice exhibited significantly lower inhibi-tion rate on starch metabolism compared with mulberry leaf extract without removal of mulberry juice. ln animal feeding trials, piglet feedstuff was added with 10% mul-berry leaf powder; compared with mulberry leaf powder without removal of mulberry juice, experimental piglets fed with mulberry leaf powder with removal of mulberry juice exhibited significantly improved weight gain and significantyl reduced diarrhea rate.

α-Glucosidase inhibitors isolated from medicinal plants

Objective:α-Glucosidase inhibitors can be used as a new class of antidiabetic drug.By competitively inhibiting glycosidase activity,these inhibitors help to prevent the fast breakdown of sugars and thereby control the blood sugar level.This study provides a wealth of information aboutα-glucosidase inhibitors isolated from medicinal plants;this knowledge will be useful in finding more potent antidiabetic candidates from the natural resources for the clinical development of antidiabetic therapeutics.Results:411 compounds exhibitingα-glucosidase inhibitory activity were summarized and isolated them from medicinal plants.The compound classes isolated include:terpenes(61)from 14 genus,alkaloids(37)from 11 genus,quinines(49)from 4 genus,flavonoids(103)from 24 genus,phenols(37)from 9 genus,phenylpropanoids(73)from 20 genus,sterides(8)from 5 genus,and other types of compounds(43).Conclusion:Compounds withα-glucosidase inhibitory activity are abundant in nature and can be obtained from several sources.They have highα-glucosidase inhibitory potential,and can be clinically developed for treating diabetes mellitus.

Identification of α-glucosidase inhibitors from Clinacanthus nutans leaf extract using liquid chromatography-mass spectrometry-based metabolomics and protein-ligand interaction with molecular docking

The present study used in vitro and in silico techniques, as well as the metabolomics approach to characterise α-glucosidase inhibitors from different fractions of Clinacanthus nutans. C. nutans is a medicinal plant belonging to the Acanthaceae family, and is traditionally used to treat diabetes in Malaysia. nHexane, n-hexane: ethyl acetate(1:1, v/v), ethyl acetate, ethyl acetate: methanol(1:1, v/v), and methanol fractions were obtained via partitioning of the 80% methanolic crude extract. The in vitro α-glucosidase inhibitory activity was analyzed using all the fractions collected, followed by profiling of the metabolites using liquid chromatography combined with mass spectrometry. The partial least square(PLS) statistical model was developed using the SIMCA P^+14.0 software and the following four inhibitors were obtained:(1) 4,6,8-Megastigmatrien-3-one;(2) N-Isobutyl-2-nonen-6,8-diynamide;(3) 1′,2′-bis(acetyloxy)-3′,4′-didehydro-2′-hydro-β, ψ-carotene; and(4) 22-acetate-3-hydroxy-21-(6-methyl-2,4-octadienoate)-olean-12-en-28-oic acid. The in silico study performed via molecular docking with the crystal structure of yeast isomaltase(PDB code: 3 A4 A) involved a hydrogen bond and some hydrophobic interactions between the inhibitors and protein. The residues that interacted include ASN259, HID295, LYS156, ARG335,and GLY209 with a hydrogen bond, while TRP15, TYR158, VAL232, HIE280, ALA292, PRO312, LEU313,VAL313, PHE314, ARG315, TYR316, VAL319, and TRP343 with other forms of bonding.

Antioxidant and α-glucosidase inhibitor activities of natural compounds isolated from Quercus gilva Blume leaves

Objective: To isolate and investigate antioxidant and α-glucosidase inhibitor compounds in the leaves of Quercus gilva Blume(Q. gilva).Methods: Dry leaves of Q. gilva were extracted with methanol and the methanolic extract was further separated by silica gel column chromatography using several solvents with increasing polarity. The antioxidant activities of the isolated compounds were evaluated using various in vitro assays: 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity, hydrogen peroxide radical scavenging activity, β-carotene bleaching assay, and reducing power assay. The α-glucosidase inhibitory assay was conducted against α-glucosidase from Saccharomyces cerevisiae.Results: Three compounds were isolated and their structures were identii ed as catechin(1), epicatechin(2), and tiliroside(3) using an instrumental analysis. Compound 2 had higher antioxidant activity with inhibitory concentrations(IC50) of(22.55 ± 2.23) μmol/L than that of quercetin, which was used as the standard, with an IC50 of(28.08 ± 2.39) μmol/L, followed by compound 1 with IC50 of(40.86 ± 3.45) μmol/L. On the other hand, compound 3 had the lowest antioxidant activity with an IC50 of(160.24 ± 8.15) μmol/L. However, compound 3 had the highest α-glucosidase inhibitory activity with an IC50 of(28.36 ± 0.11) μmol/L, followed by compounds 1 and 2 with(168.60 ± 5.15) and(920.60 ± 10.10) μmol/L, respectively.Conclusions: The results obtained for the antioxidant activities and α-glucosidase inhibitory activities in a methanolic extract from the leaves of Q. gilva coni rmed the potential of this plant as a source of natural antioxidants and antidiabetic medicine.

α-Glucosidase Inhibitory Activities of Lutein and Zeaxanthin Purified from Green Alga Chlorella ellipsoidea

α-Glucosidase inhibitors are used therapeutically to treat type-2 diabetes mellitus. Through a bioassay-guided fractionation technique, three carotenoids,(all-E)-lutein,(all-E)-zeaxanthin and(9-Z)-zeaxanthin, were purified from the green alga Chlorella ellipsoidea, in which(all-E)-lutein and(9-Z)-zeaxanthin had potent α-glucosidase inhibitory activity. IC_(50) values of(all-E)-lutein and(9-Z)-zeaxanthin were 70 and 53.5 μmol L^(-1) against Saccharomyces cerevisiae α-glucosidase, respectively, with non-competitive inhibition. In addition, IC_(50) values of(9-Z)-zeaxanthin against Bacillus stearothermophilus and rat-intestinal α-glucosidase were 805.1 and 671.2 μmol L^(-1), respectively. The K_i values of(all-E)-lutein and(9-Z)-zeaxanthin against S. cerevisiae α-glucosidase were 78.1 and 16.5 μmol L^(-1), respectively. Therefore, C. ellipsoidea carotenoids might be utilized as a novel candidate to prevent type-2 diabetes mellitus related disorders in food and medical industry.

Bioactive constituents from the leaves of Quercus phillyraeoides A.Gray for-glucosidase inhibitor activity with concurrent antioxidant activity

Severalα-glucosidase inhibitory constituents were isolated from the methanolic extract of the leaves of Quercus phillyraeoides A.Gray(Q.phillyraeoides)using a bioassay-guided fractionation technique.Further separation and purification of the methanol-soluble fraction led to the isolation of constituents with moderate and strong inhibitory activities againstα-glucosidase:α-sitosterol-d-glucoside(1)and condensed tannin fractions(2,3,4,5,and 6).Compound 1 and fractions 2-6 had inhibitory concentration(IC50)values againstm-glucosidase from Saccharomyces cerevisiae of 118.8,2.79,2.78,3.10,2.60,and 3.14μg/mL,respectively,while quercetin as the standard had an IC50 value of 4.80mg/mL.Furthermore,the significant antioxidant activities were evaluated using several assays,such as the DPPH radical scavenging,hydrogen peroxide radical scavenging,reducing power,andβ-carotene-linoleate bleaching assays,and the results suggested that the isolated constituents showed their possible application for treating the hyperglycemia-induced oxidative stress.The results of the present study showed the potential of Q.phillyraeoides as a rich source of natural antidiabetic medicine.

α-Glucosidase Inhibitory Activity-guided Identification of Compounds from Clerodendrum bungei Steud by HPLC-ESI-QTOF-MS/MS

Objective To identify the compounds withα-glucosidase inhibitory activity from Clerodendrum bungei Steud(Chou Mu Dan,臭牡丹)using HPLC-ESI-QTOF-MS/MS.Methods The ethanol extracts of Clerodendrum bungei Steud(Chou Mu Dan,臭牡丹)were partitioned with petroleum ether,ethyl acetate,n-butanol,and water.The assay forα-glucosidase inhibitory activity revealed strongα-glucosidase inhibitory activity in the ethyl acetate fraction,and the bioactive compounds present in this fraction were identified by the HPLCESI-QTOF-MS/MS method.Results A total of 29 compounds were determined,among the identified bioactive components;these included 12 phenylethanoid glycosides(compounds 5,6,17,20-22,24),7 flavonoids(compounds 10,19,23,25-28),5 phenolic acids(compounds 2-4,7,9),and 5 other compounds.Compounds 2-4,7,9-10,12-13,15,19,and 26,with a potentialα-glucosidase inhibitory activity,have been reported previously.Conclusions Our results show that the methodology used in this study is feasible,credible,and rapid in identifying known compounds and also for characterizing new natural glucosidase inhibitory candidates from Clerodendrum bungei Steud(Chou Mu Dan,臭牡丹).

Colorimetric detection of α-glucosidase activity using Ni-CeO_(2)nanorods and its application to potential natural inhibitor screening

In this work,we established an exceptionally facile method for the preparation of Ni-CeO_(2)nanorods in a kind of deep eutectic solvents(DESs)composed of l-proline and Ce(NO_(3))_(3)·6H_(2)O.First,Ni-CeO_(2)nanorods were successfully prepared by adding Ni(NO_(3))_(3)·6H_(2)O to DESs.Then,we found that Ni-CeO_(2)nanorods prepared in DESs have more prominent oxidase-like activity than pure CeO_(2).The outstanding catalytic activity of Ni-CeO_(2)could be ascribed to its high Ce^(3+)/Ce^(4+)ratio.As a proof-of-concept application,the Ni-CeO_(2)nanorods were successfully acted as a colorimetric platform for the sensitive determination of ascorbic acid andα-glucosidase activity,which displays excellent analytical performance.Moreover,this sensing platform was applied for screening naturalα-glucosidase inhibitors,such as terpenoids from natural products.The results indicated that ursolic acid and oleanolic acid had good inhibitory rates.This strategy not only provides a new way to construct more kinds of nanomaterials from DESs,but also offers a facile and effective tool to screen theα-glucosidase natural inhibitors as potential anti-diabetic drugs.

Determination of α-glucosidase inhibitors from Scutellaria baicalensis using liquid chromatography with quadrupole time of flight tandem mass spectrometry coupled with centrifugal ultrafiltration

The present study aimed at identifying potential lead compounds for diabetes mellitus drug discovery. We developed a novel method involving centrifugal ultrafiltration separation subsequent liquid chromatography with quadrupole time of flight tandem mass spectrometry （LC-Q/TOF-MS/MS） determination to screen a-glucosidase inhibitors in complex Scutellaria baicalensis Georgi （SBG） extract. By adding a second filter to the screening process, the level of non-specific binding of Compounds 1, 3, 10 and 11 was significantly decreased, and the level of non-specific binding of Compounds 5 and 15 also was reduced. As a result, five flavonoids identified as baicalein, baicalein, wogonin, chrysin, and oroxylin A, were rapidly found to interact with α-glucosidase and possess potent anti-a-glueosidase aetivity in vitro. Specific binding of ligands to a-glucosidase was demonstrated though the proposed method and the ligands could be ranked in order of affinity for α-glucosidase, which were corresponded to the order of inhibitory activity in vitro. In conclusion, our results indicated that the developed method is a rapid and effective screening method for rat intestinal α-glucosidase inhibitors from complex herbal medicines such as SBG.

Chemical Constituents from Mentha haplocalyx Briq.(Mentha canadensis L.)and Theirα‑Glucosidase Inhibitory Activities

Mentha haplocalyx(Mentha canadensis)is widely used as a medicinal plant in traditional Chinese medicine,and the extracts of its aerial parts are found to signifcantly inhibit the activity ofα-glucosidase with an IC_(50) value of 21.0μg/mL.Bioactivity-guided isolation of the extracts aforded two new compounds(1 and 2),together with 23 known ones(3-25).Their structures were established by extensive spectroscopic analyses(1D and 2D NMR,MS,IR and UV).Compounds 1-17 and 21-25 were evaluated for theirα-glucosidase inhibitory activities.Compound 11 was the most active ones with an IC_(50) values of 83.4μM.These results verify theα-glucosidase inhibitory activity of M.haplocalyx(M.canadensis)and specify its active compounds for the frst time.

α-Glucosidase immobilization on functionalized Fe_3O_4 magnetic nanoparticles for screening of enzyme inhibitors

Magnetic nanoparticles(MNPs) are widely used for the immobilization of enzyme owing to the unique properties such as good biocompatibility and rapid separation. Herein, we used Fe_3O_4 magnetic nanoparticles(Fe_3O_4 MNPs) as the carrier core with(3-aminopropyl)triethoxysilane(APTES)modification by our approach, in which a-glucosidase was stereoscopically immobilized on the surface of Fe_3O_4 MNPs via covalent binding. The result of immobilization was characterized by scanning electron microscope(SEM) and fourier transform-infrared spectroscopy(FT-IR). Then we optimized some key parameters of the immobilization reaction, including the ratio of MNPs to enzyme, GA concentration,crosslinking time and immobilization time. Moreover, under the optimal conditions, pH tolerance,thermo stability and reusability of the immobilized enzyme were investigated and compared with the free one. In order to evaluate the change of the affinity of the enzyme to its specific substrate after immobilization, the Michaelis-Menten constant(K_m) was also studied. Finally, the immobilized α-glucosidase combining with high performance liquid chromatography-tandem mass spectrometry technique(HPLC-MS/MS) was applied to screen and identify eight inhibitors from Polygonum cuspidatum extract. These results indicated that the established method had the broad prospects for biotechnological applications.

Novel carbohydrate-triazole derivatives as potentialα-glucosidase inhibitors

A series of novel pyrano[2,3-d]trizaole compounds were synthesized and theirα-glucosidase inhibitory activities were evaluated by in vitro enzyme assay.The experimental data demonstrated that compound 10 f showed up to 10-fold higher inhibition(IC5074.0±1.3μmol·L-1)than acarbose.The molecular docking revealed that compound 10 f could bind toα-glucosidase via the hydrophobic,π-πstacking,and hydrogen bonding interactions.The results may benefit further structural modifications to find new and potentα-glucosidase inhibitors.

Tsaokols A and B,unusual flavanol-monoterpenoid hybrids asα-glucosidase inhibitors from Amomum tsao-ko

Tsaokols A(1)and B(2),two complicated flavanol-monoterpenoid hybrids,were isolated from the dried fruits of Amomum tsao-ko under the guidance of LCMS and bioassay.Their structures were determined by extensive spectroscopic analyses and electronic circular dichroism(ECD)calculations.Compounds 1 and2 shared a flavanol backbone fused with 5/7 and 5/6 bicyclic monoterpenoid scaffolds,which were biogenetically condensed by Michael addition and acetalization.Compounds 1 and 2 exhibited significantα-glucosidase inhibitory activity with IC_(50)values of 18.8 and 38.6μmol/L(acarbose,IC_(50)=213μmol/L).Docking study supported the strong interactions of 1 and 2 bonding with enzyme by mainly hydrophobic and hydrogen-bond effects.Compounds 1 and 2 could be fast distinguished by the diagnostic ions at m/z 289 and 313 in negative MS^(2)experiments.

Discovery of pyrogallol thermal reaction products from a model process of roasting coffee beans as potentα-glucosidase inhibitors

The roasting process of pyrogallol,a polyphenol compound distributed in coffee beverages,significantly enhanced itsα-glucosidase inhibitory activity.In this study,a bioassay-guided isolation of the thermal reaction products of pyrogallol led to the identification of two potentα-glucosidase inhibitors,4-4′dimer of pyrogallol(4,4′-DP)and 4-5′dimer of pyrogallol(4,5′-DP).Theirα-glucosidase inhibitory activity was higher than that of pyrogallol,as evidenced by comparing the IC_(50)values(206.2±1.2μM for 4,4′-DP,187.6±2.6μM for 4,5′-DP,2660±60.1μM for pyrogallol).And the roasting products were more potentα-glucosidase inhibitors compared to acarbose(IC_(50)=695±12.7μM).Enzyme kinetics demonstrated that 4,4′-DP and 4,5′-DP inhibitedα-glucosidase in an uncompetitive and a non-competitive manner,respectively.Docking simulations revealed that the main interaction forces between these two compounds andα-glucosidase were hydrogen bonding and hydrophobic effect.These results suggested that a simple roasting process might increase theα-glucosidase inhibitory activity of pyrogallol-containing foods such as coffee beverages.

Metal complexes of anthranilic acid derivatives: A new class of noncompetitive α-glucosidase inhibitors

Metal complexes of anthranilic acid derivatives that constitute a novel class of non-sugar-type α- glucosidase inhibitors were synthesized and assessed in vitro for inhibitory activity. All of the AgO） complexes （9-16） inhibited α-glucosidase at the nanomolar scale, while 3,5-dichloroanthranilic acid silver（1） （9） was the most potent （ICso = 3.21 nmol/L）. Analysis of the kinetics of enzyme inhibition indicated that the mechanism of the newly prepared silver complexes was noncompetitive. The structure-activity relationships were also analyzed, and thev are discussed in this report.

微生物发酵在天然α-葡萄糖苷酶抑制剂研究中的应用进展

糖尿病一直是严重威胁人类健康及生活质量的疾病,α-葡萄糖苷酶抑制剂(α-glucosidase inhibitors,AGI)是治疗Ⅱ型糖尿病的首选药物,但目前临床常用的AGI药物受到成本相对较高且有显著不良反应的困扰。降糖植物是获得低副作用、多靶点、高催化活性的天然AGI的重要来源,利用微生物强大的代谢网络和丰富的酶系提高降糖植物中AGI活性物质含量及生物活性、经过生物转化获得新型AGI已成为研究热点。探究了微生物发酵对降糖植物AGI活性物质的转化作用,并对微生物发酵在提高降糖植物α-葡萄糖苷酶抑制活性的应用进展进行了综述,为进一步深入挖掘和研发高效安全的天然AGI药物提供了参考。

Surface engineering of carbon dots for highly sensitive α-glucosidase assay and inhibition evaluation

Monitoringα-glucosidase(α-Glu)activity is of great significance for the early diagnosis of typeⅡdiabetes.Here the blue fluorescent carbon dots(CDs)were integrated with two different recognizing molecules,β-cyclodextrin and phenylboronic acid,for assembling a multifunctional CDs(mCDs)nanoplatform for sensitively analyzingα-Glu and its inhibitors.The hydrolyzed product of 4-nitrophenyl-α-D-glucopyranoside(α-Glu substrate),p-nitrophenol,could efficiently quench the fluorescence of mCDs due to its cooperative molecular recognition withβ-cyclodextrin and phenylboronic acid.The mCDs could be utilized for the detection ofα-Glu activity with the limit of detection of 0.030 U/L.Moreover,the presentα-Glu detection platform revealed a high selectivity,and other natural enzymes showed scarcely any effect on the present mCDs system.The proposed method could be facilely used to screenα-Glu inhibitors with satisfying performance.The rational mCDs is expected to supplement more comprehensive biosensing platforms for highly sensitive and specific recognition of disease-relevant biomarkers with clinical importance.

A colorimetric method for α-glucosidase activity assay and its inhibitor screening based on aggregation of gold nanoparticles induced by specific recognition between phenylenediboronic acid and 4-aminophenyl-α-D- glucopyranoside

A colorimetric method has been established for a-glucosidase activity assay and its inhibitor screening. The method is based on the specific recognition between 1,4-phenylenediboronic acid （PDBA） and 4-aminophenyl-a-D-glucopyranoside （pAPG）, which may induce aggregation of pAPG-functionalized gold nano- particles （AuNPs） to achieve color change of the test solution. Because pAPG is the substrate of α-glucosidase, the aggregation of AuNPs will be influenced by α-glucosidase since there is no coordination reactivity between PDBA and 4-aminobenzene, the hydrolyzed product of pAPG catalyzed by the enzyme. Therefore, a simple and easily-operated colorimetric method for the assay of a-glucosidase activity can be developed. Under the optimized experimental conditions, the ratios of absorbance at a wavelength of 650 nm to that at 520 nm vary linearly with the α-glucosidase activity within a range from 0.05 to 1.1 U/mL with a lowest detection limit of 0.004 U/mL. Moreover, using the proposed method, the inhibition effect of gallic acid and quercetin on a-glucosidase activity can be tested with IC50 values of 1.16 mM and 1.82 μM, respectively. Thus, the method has a great potential not only for the detection of a-glucosidase activity, but also for the screening of its inhibitors.

A New Alkaloid from Bombycis Feculae and Its α-Glucosidase Inhibitory Activity

Objective To study the chemical constituents of Bombycis Feculae.Methods Chemical constituents were isolated by HPLC-ELSD.The structures of the isolated compounds were determined by spectral means.Results Two compounds were isolated and identified as 1-deoxynojirimycin(1)and(2R,3R,5R)-2-(hydroxymethyl) piperidine-3,5-diol,named as 1,3-dideoxygalatonojirimycin(2).Conclusion Compound 2 is a new alkaloid.The extract of Bombycis Feculae,compound 1 and compound 2 show inhibitory activities againstα-glucosidase.