Antioxidant andα-glucosidase inhibitiory activity of Cercis chinensis flowers

Antioxidant andα-glucosidase inhibitiory active compounds of Cercis chinensis flowers were investigated with bio-assay guiding method.Ethyl acetate fraction(CLEa)and n-butanol fraction(CLBu)exhibited antioxidant andα-glucosidase inhibitiory activity in vitro,and the corresponding active fractions,EaFr.3,EaFr.5 and BuFr.1,exhibited higher antioxidant andα-glucosidase inhibitiory activity than those of other fractions.Eight compounds,ethyl gallate(1),stearic acid(2),docosanoic acid(3),5α-stigmast-9(11)-en-3β-ol(4),kaempferol-3-O-α-rhamnopyranoside(5),vanillic acid(6),fisetin(7),andβ-sitosterol(8),were isolated and identified from CLEa and CLBu.Ethyl gallate shown the highest antioxidant activity by scavenging DPPH radical and reducing ferric compared.Docosanoic acid and vanillic acid shown strongerα-glucosidase inhibitory activity than that of acarbose.

Antioxidant,antimicrobial,and α-glucosidase inhibitory activities of saponin extracts from walnut(Juglans regia L.) leaves

Objective:To investigate the relationship between triterpenoid saponin content and antioxidant,antimicrobial,and α-glucosidase inhibitory activities of 70%ethanolic,butanolic,aqueous,supernate and precipitate extracts of Juglans regia leaves.Methods:Triterpenoid saponins of different Juglans regia leaf extracts were measured by the vanillin method.Antioxidant activity was evaluated against DPPH and ABTS free radicals.We also assessed α-glucosidase inhibitory and antimicrobial activities of the leaf extracts.Pearson’s correlation coefficient was evaluated to determine the correlation between the saponin content and biological activities.Results:The butanolic extract was most effective against DPPH with an IC50of 6.63μg/mL,while the aqueous extract showed the highest scavenging activity against ABTS free radical with an IC50of 42.27μg/mL.Pearson’s correlation analysis indicated a strong negative correlation (r=-0.956) between DPPH radical scavenging activity (IC50) and the saponin content in the samples examined.In addition,the aqueous extract showed the best α-glucosidase inhibitory activity compared with other extracts.All the extracts had fair antibacterial activity against Bacillus subtilis,Escherichia coli,and Klebsiella pneumoniae except for the aqueous extract.Conclusions:Juglans regia extracts show potent antioxidant,antimicrobial,and α-glucosidase inhibitory activities.There is a correlation between saponin levels in Juglans regia leaf extracts and the studied activities.However,additional research is required to establish these relationships by identifying the specific saponin molecules responsible for these activities and elucidating their mechanisms of action.

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.

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.

Evaluation of bioactive flavonoids in Citri Reticulatae Pericarpium from different regions and its association with antioxidant andα-glucosidase inhibitory activities

Background:To explore the differences of 14 batches of Citri Reticulatae Pericarpium from different regions.Methods:The main aim of this study was to develop a high-performance liquid chromatography method-photodiode array detection for determining the contents of five flavonoids and the chromatographic fingerprints of Citri Reticulatae Pericarpium from different regions.Theα-glucosidase inhibitory activities and antioxidant properties of Citri Reticulatae Pericarpium,based on free-radical scavenging assays against 1,1-diphenyl-2-picrylhydrazyl,2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid),and hydroxyl radicals,were estimated and compared.Results:Among the tested compounds,the content of hesperidin(13.386-68.235 mg/g)was the highest and that of hesperitin(0.045-0.277 mg/g)was the lowest.In comparing different sources of Citri Reticulatae Pericarpium,the contents of narirutin in Citri Reticulatae Pericarpium from Guangdong(0.824-0.851 mg/g)and Sichuan(1.069-1.204 mg/g)provinces of China were lower than in other provinces.In contrast,nobiletin(8.429-12.237 mg/g)and tangeretin(3.947-4.613 mg/g)were most abundant in Guangdong sources of Citri Reticulatae Pericarpium,followed by samples from Sichuan Province(nobiletin:6.761-7.658 mg/g;tangeretin:3.422-3.933 mg/g).Correlation analysis showed that nobiletin and tangeretin were the main contributors to the antioxidant capacity,and narirutin was the main active component inhibiting theα-glucosidase activity of Citri Reticulatae Pericarpium.Conclusion:This work revealed that the intrinsic quality of Citri Reticulatae Pericarpium was affected by different growing regions,which provides a scientific basis for controlling the quality of Citri Reticulatae Pericarpium and rationally developing and utilizing Citri Reticulatae Pericarpium.

DISTRIBUTION OF β-GLUCOSIDASE ACTIVITIES IN THE SOUTH CHINA SEA

Distribution of extracellular β-glucosidase activity (β-GlcA), bacteria abundance andTOC were investigated during tbe SCSMEX98 cruise in May and June 1998 in the South China Sea. Re-sults showed that β-GlcA varied significantly in both vertical and horizontal distribution. Hydrolysis rateranged from under detectable limit to 29% /h. In most cases, β-GlcA was highest in surface water; some-times there was a second-highest value at the bottom of the euphotic zone. Temperature controlled experi-ments showed that low temperature could significantly decrease β-GlcA; but that the low β-GlcA in

Cucurbitane-Type Triterpene Glycosides from Momordica charantia and Their α-Glucosidase Inhibitory Activities

Ten cucurbitane-type triterpene glycosides,including five new compounds named charantosides H(1),J(2),K(3),momor-characoside A(4),goyaglycoside-l(5),and five known compounds(6-10),were isolated from the EtOAc extract of Momor-dica charantia fruits.The chemical structures of these compounds were identified by 1D and 2D NMR and HRESIMS spectroscopic analyses.Configurations of new compounds were determined by ROESY correlations and comparison of their 13C NMR data with literature reported values.All compounds were evaluated for their inhibition againstα-glucosidase,in which compounds 2,5,7,8,9 showed moderate inhibitory activities with IC50 values ranging from 28.40 to 63.26μM comparing with the positive control(acarbose,IC5087.65±6.51μM).

Enzymatic activities and kinetic properties of β-glucosidase from selected white rot fungi

Beta-glucosidase is among the suite of enzymes produced by white rot fungi (WRF) to biodegrade plant biomass. This study investigated the enzymatic activities and kinetic properties of β-glucosidase from seventeen WRF comprised of the following species from various geographical locations: Pleurotus ostreatus, Auricularia auricular, Polyporus squamosus, Trametes versicolor, Lentinula edodes, and Grifola frondosa. All the WRF studied showed β-glucosidase activities. Significant variations in protein and carbohydrate contents were also recorded. Beta-glucosidase activities after 30 min of incubation ranged from 6.4 μg (T. versicolor) to 225 μg (G. frondosa). The calculated kinetic constant (Km) ranged from 0.47 μM (A. auricular-1120) to 719 μM (L. edodes-7). The Vmax depending on the kinetic transformation model ranged from 0.21 μg·min-1 (T. versicolor) to 9.70 μg·min-1 (G. frondosa-28). Beta-glucosidase activities also exhibited pH optima between 3.5 and 5.0 while temperature optima were between 60°C and 70°C with some media exhibiting a secondary temperature peak at 90°C attributable to the presence of thermostable isoenzyme. WRF if appropriately screened and purified can be harnessed to potentially improve the bio-conversion of cellulose to glucose and also facilitate efficient plant biomass biodegradation and production of useful plant bio-products.

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.

α-Glucosidase inhibitor produced by an endophytic fungus, Xylariaceae sp. QGS 01 from Quercus gilva Blume

Xylariaceae sp.QGS 01,an endophytic fungus isolated from the stem of Quercus gilva Blume showed high-glucosidase inhibitory activity.α-Glucosidase inhibitor have the role as one of carbohydrate-hydrolyzing enzymes to postpone absorption of glucose in the digestive organs.The α-glucosidase inhibitor constituents were isolated from the ethyl acetate extract of the mycellium of endophytic fungi Xylariaceae sp.QGS 01 using a bioassay-guided fractionation technique.Further separation and purification of the active fraction led to the isolation of constituents with strong inhibitory activities against-glucosidase:8-hydroxy-6,7-dimethoxy-3-methylisocoumarine(1)with inhibitory concentration(IC50)values against-glucosidase from Saccharomyces cerevisiae of 41.75μg/mL,while quercetin as the standard had an IC50 value of 4.80g/mL.The results of the present study showed that the endophytic fungus Xylariaceae sp.QGS 01 is potentially a rich source of antidiabetic medicine.

In vitro Pharmacological Activity of Chromenes in Disk of Helianthus annuus

[Objectives]The anti-tumor,anti-bacterial,anti-acetylcholinesterase and anti-α-glucosidase activity in vitro of five chromenes isolated from Helianthus annuus disk was studied,in order to provide reference for the development and utilization of H.annuus disk resources.[Methods]The effect of different concentrations of chromenes on the survival rate of leukemia HL-60 cells,lung cancer A549 cells,liver cancer SMMC-7721 cells,breast cancer MCF-7 cells and colon cancer SW480 cells was detected by MTS method,and the IC50 was calculated.The inhibitory activity of chromenes against Escherichia coli,Staphylococcus aureus subsp.aureus,Salmonella enterica subsp.enterica,Pseudomonas aeruginosa and Candida albicans was detected by microdilution method.The DTNB substrate method was used to detect the inhibitory activity of chromenes on acetylcholine.The PNPG substrate method was used to detect the inhibitory activity of chromenes onα-glucosidase.[Results]The five chromenes had no obvious in vitro inhibitory activity on the five kinds of tumor cells,with IC50 greater than 40μM.The five chromenes had no obvious in vitro inhibitory activity against the four kinds of bacteria and C.albicans.The five chromenes had certain inhibitory activity on acetylcholinesterase,and among them,6-acetyl-2,2-dimethylchromene and 6-acetyl-7-hydroxy-2,3-dimethylchromene showed strong inhibitory activity on acetylcholinesterase,with IC50 of 28.253 and 16.945μM,respectively,both smaller than that(0.275μM)of the positive control tacrine(P<0.01).The five chromenes showed good inhibitory effect onα-glucosidase,and among them,7-hydroxy-6-hydroxyacetyl-2,2-dimethylchromene and 6-acetyl-7-hydroxy-2,3-dimethylchromene had stronger inhibitory activity,with IC50 of 20.240 and 21.052μM,respectively,significantly better than that(169.780μM)of the positive control acarbose(P<0.01).[Conclusions]The five chromenes in H.annuus disk have certain in vitro inhibitory activity against acetylcholinesterase andα-glucosidase and certain potential in fighting neurodegenerative diseases and diabetes.

Rapid identification of stigmastane-type steroid saponins from Vernonia amygdalina leaf based onα-glucosidase inhibiting activity and molecular networking

Steroid saponins are secondary metabolites with multiple medicinal values that are found in large quantities in natural medicines,especially Vernonia amygdalina,a famous nature medicine for the treatment of tonsillitis,diabetes,pneumonia.The current study was designed to combine molecular networking(MN)with diagnostic ions for rapid identification ofΔ^(7,9(11))stigmastane-type saponins which were theα-glucosidase inhibitory active substances in V.amygdalina.First,theα-glucosidase inhibitory activities of fiveΔ^(7,9(11))stigmastane-type steroid saponins that were previously isolated were screened,which indicated that theΔ^(7,9(11))stigmastane-type steroid saponin was one of the active constituents responsible for ameliorating diabetes.Furthermore,a strategy was proposed to identify stigmastane-type steroid saponins and verify the plausibility of derived fragmentation pathways by applying MN,MolNetEnhancer and unsupervised substructure annotation(MS2LDA).Based on this strategy,other sevenΔ^(7,9(11))stigmastane-type steroid saponins were identified from this plant.Our research provide scientific evidence for the antidiabetic potential of the steroid saponin-rich extract of V.amygdalina leaf.

Flavonoids from Litchi(Litchi chinensis Sonn.) Seeds and Their Inhibitory Activities on α-Glucosidase

With the bioactivity-guided method,a new flavanone glycoside,together with nine known flavonoids were isolated from 50% aqueous ethanol of litchi（Litchi chinensis Sonn.） seeds.The chemical structure of the new compound was elucidated via 1D and 2D nuclear magnetic resonance（NMR） techniques and mass spectrometry to be （2S）-pinocembrin-7-O-（6＂-O-α-L-arabinosyl-β-D-glucopyranoside）（1）,and the nine known compounds were determined to be quercetin（2）,phlorhizin（3）,pinocembrin-7-O-glucoside（4）,kaempferol-7-O-β-D-glucopyranoside（5）,onychin（6）,nairutin（7）,narcissin（8）,pinocembrin-7-O-[（6＂-O-β-D-glucopyranoside）-β-D-glucopyranoside]（9） and pinocembrin-7-O-[（2＂,6＂-di-O-α-L-rhamnopyranosyl）-β-D-glucopyranoside]（10）.Some of the isolated flavonoids were tested for their inhibitory effects on α-glucosidase.And compounds 2 and 3 showed stronger inhibitory activity than positive control.

Highly exposed Cu active sites as efficient peroxidase mimics for colorimetric analysis

Nanozymes are nanomaterials with intrinsic enzyme-mimic activity,but their large-scale application is generally limited by their low catalytic activity.Herein,we demonstrated that highly exposed Cu active sites on two-dimensional(2D)nitrogen-doped carbon(Cu_(x)/NC)can serve as efficient peroxidase-like(POD)catalysts with high atomic utilization.Specially,the uniformly distributed Cu active sites could react with H_(2)O_(2)to produce singlet oxygen(^(1)O_(2))under acidic conditions,which can efficiently oxidizes colorless 3,3',5,5'-tetramethylbenzidine(TMB)to blue oxidized TMB(oxTMB).Among various Cu_(x)/NC nanozymes studied,the Cuo.14/NC exhibited smaller maximum catalytic velocities(V_(max))and Menten constant(K_(m))for TMB and H_(2)O_(2).Benefiting from the highly active peroxidase-like activity,the Cu_(0.14)/NC nanozyme could be successfully applied for the hydroquinone(HQ)and ascorbic acid(AA)detection applications through the inhibitory effect of HQ and AA.More interestingly,α-glucosidase(α-Glu)detection sensing platform could be constructed based on HQ as a signal transmitter,with the detection range ranging from O to 12 U/L and the minimum detection limit being 0.68 U/L.This work provides not only an idea for the rational design of highly exposed Cu active sites but also fabricate an effective detection sensing platform forHQ,AA,andα-Glu detection.

窄叶蓝盆花花序化学成分及其抗氧化和抑制α-葡萄糖苷酶活性的研究

研究蓝盆花Scabiosa comosa Fisch花序的化学成分,及其抗氧化活性和抑制α-葡萄糖苷酶活性.反复采用硅胶柱色谱,RP-C18柱色谱,Sephadex LH-20,MCI,制备型高效液相色谱等方法分离纯化窄叶蓝盆花花序的化学成分,利用多种波谱技术(UV,NMR,LC-MS)鉴定化合物结构.进一步对这些化合物的DPPH游离基清除率和α-葡萄糖苷酶活性抑制率进行了测定.本实验从蓝盆花花序中分离鉴定出10个化合物,7个酚类化合物,2个萜类化合物和1个甾醇化合物.其中芹菜素-4′-O-β-葡萄糖苷(2),芹菜素-7-O-α-阿拉伯糖(1-6)-β-葡萄糖苷(6)和3β,23-二羟基乌索-12-烯-28-酸(9)为首次从本属植物中分离得到.体外活性实验结果显示,木犀草素(3),木犀草素-7-O-β-葡萄糖苷(4)和绿原酸(7)具有显著的清除DPPH游离基活性,EC50值分别为19、43和26μg·mL-1;另外,黄酮苷元芹菜素(1)和萜类化合物熊果酸(8)及3β,23-二羟基乌索-12-烯-28-酸(9)具有抑制α-葡萄糖苷酶的活性.

Comparative evaluation of polysaccharides isolated from Astragalus,oyster mushroom,and yacon as inhibitors of α-glucosidase

The incidence of diabetes has increased considerably, and become the third serious chronic disease following cancer and cardiovascular diseases. Though acarbose, metformin, and 1-deoxynojirimycin have good efficacy for clinical application as hypoglycemic drugs, their expensive costs and some degree of side effects have limited their clinical application. Recently, increasing attention has concentrated on the polysaccharides from natural plant and animal sources for diabetes. In order to illustrate the pharmaceutical activity of polysaccharides as natural hypoglycemic agents, polysaccharides isolated from Astragalus, oyster mushroom, and Yacon were evaluated for their inhibitory effects on α-glucosidase. Polysaccharides were extracted and purified from Astragalus, Oyster mushroom, and Yacon with hot water at 90 °C for 3 h, respectively. The total sugar content of the polysaccharide was determined by the phenol-sulfuric acid method. The α-glucosidase inhibitory activity was measured by the glucose oxidase method. The results exhibited that the inhibitory effects on α-glucosidase were in decreasing order, Astragalus > oyster mushroom > Yacon. The α-glucosidase inhibition percentage of Astragalus polysaccharide and oyster mushroom polysaccharide were over 40% at the polysaccharide concentration of 0.4 mg·mL-1. The IC50 of Astragalus polysaccharide and oyster mushroom polysaccharide were 0.28 and 0.424 mg·mL-1, respectively. The information obtained from this work is beneficial for the use polysaccharides as a dietary supplement for health foods and therapeutics for diabetes.

Vitellaria paradoxa nutshells from seven sub-Saharan countries as potential herbal medicines for treating diabetes based on chemical compositions, HPLC fingerprints and bioactivity evaluation

The aim of the study was to determine the feasibility of the Vitellaria paradoxa nutshell as a new medicinal resource for treating diabetes. A total of forty-one compounds were identified by HPLC-DAD-Q-TOF-MS and phytochemical methods in V. paradoxa nutshell methanol extract. Based on HPLC fingerprints, four characteristic constituents were quantified and the origin of twenty-eight V. paradoxa nutshells from seven sub-Saharan countries was compared, which were classified into three groups with chemometric method. Twenty-eight samples contained high total phenolic content, and exhibited moderate-higher antioxidant activity and strong α-glucosidase inhibitory activity. Furthermore, all fractions and isolated compounds were evaluated for their antioxidant and α-glucosidase inhibitory activities, and α-glucosidase inhibitory action mechanism of four characteristic constituents including protocatechuic acid, 3, 5, 7-trihydroxycoumarin,(2 R, 3 R)-(+)-taxifolin and quercetin was investigated via molecular docking method, which were all stabilized by hydrogen bonds with α-glucosidase. The study provided an effective approach to waste utilization of V. paradoxa nutshell, which would help to resolve waste environmental pollution and provide a basis for developing potential herbal resource for treating diabetes.

Screening potential α-glucosidase inhibitors from Anemarrhena asphodeloides using response surface methodology coupled with grey relational analysis

Objective: To screen potential α-glucosidase inhibitors from Anemarrhena asphodeloides.Methods: Response surface methodology employing Box-Behnken design was used to optimize conditions for the extraction of α-glucosidase inhibitory active compounds from A. asphodeloides. The powders(20.0 g) of A. asphodeloides were extracted under the optimized conditions. The extract was applied to a D-101 macroporous resin column. It was eluted with ethanol and water to give six fractions. Compounds from the active fraction were identified by UPLC-Q-TOF-MS. The structure-activity relationship was discussed based on grey relational analysis.Results: The optimum extraction conditions were as follows: ethanol concentration, 100%; extraction temperature, 51 ℃; and solvent to solid ratio, 23 mL/g. It indicated that the active compounds were concentrated into 80% ethanol fraction. Twenty five steroid saponins from 80%ethanol fraction were identified by UPLC-Q-TOF-MS. Peaks 19 and 23 were tentatively identified as new structures. The predicted α-glucosidase inhibitory activities of the compounds were 7 > 2 > 1 > 22 > 23 > 3 > 9 > 21 > 24 > 4 > 13 > 8 > 14 > 16 > 17 > 25 > 6 > 19.Conclusion: The fraction eluted by 80% ethanol showed the best inhibitory activity. After analyzing the data of UPLC-Q-TOF-MS, 25 steroid saponins were tentatively identified in this fraction.

Screening of probiotics with efficient α-glucosidase inhibitory ability and study on the structure and function of its extracellular polysaccharide

Inhibition ofα-glucosidase activity is an important strategy in lowering the concentration of blood sugar.In this paper,using domestic and foreign characteristic food-derived substances as the sources of lactobacillus,the performance of them were evaluated by measuring the strains’α-glucosidase inhibitory ability.Finally,the cell-free extracellular supernatants(CFS)of Lactobacillus rhamnosus LB1lac10 was determined to have the highest α-glucosidase inhibition ability.Based on the Nanopore third-generation sequencing technology platform,the genome of LB1lac10 was sequenced and functional gene annotation was performed.After that,the biological activity and structural composition of the exopolysaccharide produced by L.rhamnosus LB1lac10 were studied.The purified exopolysaccharide EPS1-1 also showed efficientα-glucosidase inhibitory ability.The structure and conformation characteristics of EPS1-1 were further analyzed.The EPS1-1 from L.rhamnosus LB1lac10 had a molecular weight of 88,650 Da,and it was mainly composed of mannose,glucuronic acid,glucose,xylose,galactose,and arabinose.From the FT-IR and NMR analyses,EPS1-1 had functional groups of a typical polysaccharide structure and contained two types of glycosidic bonds with α-configuration pyranose.The main glycosidic bond corresponded to→4)-α-D-Glcp-(1→,which might be an important reason why EPS1-1 could inhibit α-glycosidase.Thermodynamic studies showed that EPS1-1 had high heat resistance to meet the needs of food processing.The results suggested that L.rhamnosus LB1lac10 could be used as a potential probiotic to lower blood sugar,and the EPS1-1 has the potential to serve as a naturalα-glycosidase inhibitor to regulate the concentration of blood glucose.

Termitomenins F and G,Two New Lignan Glucosides from Terminalia chebula var.tomentella(Kurz)C.B.Clarke

The extensive chemical investigation on the branches and leaves of Terminalia chebula var.tomentella(Combretaceae)led to the isolation of two new lignan glucosides with a furofuran skeleton,termitomenins F(1)and G(2).In addition,19 known compounds including five lignan glucosides(3-7),six hydrolyzable tannins(8-13)and eight simple phenolics(14-21)were also identified.Their structures were determined by comprehensive spectroscopic analyses.It is noted that 8 and 9 were C-glycosidic hydrolyzable tannins with one hexahydroxydiphenoyl and one gallagyl group linked to an open-chain glucosyl C-1/O-2/O-3 and O-4/O-6,respectively,which were rarely found in plants.Nine known compounds,6-9,13,and 18-21,were procured from the titled plant for the first time,while 3-5,10-12 and 14-17 were also found in the fruits.Notably,the known hydrolyzable tannins 8-13 exhibited strongerα-glucosidase inhibitory activities with IC_(50) values ranging from 0.10 to 3.12μM,than the positive control,quercetin(IC_(50)=9.38±0.33μM).