Design and synthesis of inositolphosphoglycan putative insulin mediators

The binding modes of a series of molecules, containing the glucosamine (1-->6) myo-inositol structural motif, into the ATP binding site of the catalytic subunit of cAMP-dependent protein kinase (PKA) have been analysed using molecular docking. These calculations predict that the presence of a phosphate group at the non-reducing end in pseudodisaccharide and pseudotrisaccharide structures properly orientate the molecule into the binding site and that pseudotrisaccharide structures present the best shape complementarity. Therefore, pseudodisaccharides and pseudotrisaccharides have been synthesised from common intermediates using effective synthetic strategies. On the basis of this synthetic chemistry, the feasibility of constructing small pseudotrisaccharide libraries on solid-phase using the same intermediates has been explored. The results from the biological evaluation of these molecules provide additional support to an insulin-mediated signalling system which involves the intermediacy of inositolphosphoglycans as putative insulin mediators.     

Study of enzyme inhibitory activities by dipyridamole

Inhibitory activities of Dipyridamole (DPM, 2,6-bis(diethanolamino)-4,8-dipiperidinopyrimido(5,4-d)py rim idine) against xanthine oxidase (XO), carbonic anhydorase (CA) and monoamine oxidase (MAO) were studied, in vitro. DPM did not inhibit XO and CA, but it strongly inhibited MAO. The type of inhibition by DPM against MAO with respect to benzylamine as a substrate was uncompetitive.     

三嗪噁二唑基吡唑衍生物抑酶活性的QSAR模型

基于拓扑化学理论,原子类型电拓扑态指数(Mk)被用于表征18种三嗪噁二唑基吡唑衍生物的化学微环境。采用最佳变量子集回归方法,分别建立上述化合物对蛋白酪氨酸磷酸酯酶1B(PTP1B)、细胞分裂周期25磷酸酯酶B(Cdc25B)的抑酶活性(P_t、C_d)与Mk的定量构效关系(QSAR)模型。它们的最佳三元QSAR模型的判定系数(R~2)依次为0.896、0.828,逐一剔除法交叉验证相关系数(R_(cv)~2)依次为0.830、0.688。经R_(cv)~2、VIF、FT、AC等检验,该模型具有良好的稳健性及预测能力。经训练集验证,上述模型均具有良好的外部预测能力。模型显示,影响Pt、Cd的因素既有不同的结构基团(-CH_3、-O-、-NH_2和芳环中-N=),也有相同的因素(芳环中-C=)。     

Combinatorial library of five-membered iminocyclitol and the inhibitory activities against glyco-enzymes.

BACKGROUND: Oligosaccharide processing enzymes are important classes of catalysts involved in synthesizing specific oligosaccharide structures on proteins and sphingolipids. Development of specific inhibitors of such enzymes is of current interest as these inhibitors may be used to control cellular functions. Five-membered iminocyclitols have been shown to be potent inhibitors of such enzymes. Since a rational design and synthesis of inhibitors is often extremely difficult due to the limited information regarding the structure of the active site, we carried out a combinatorial library approach. RESULTS: To create diversity, we decided to use an aldehyde group of a protected iminocyclitol for reductive amination and the Strecker reaction. After transformation of the nitrile group introduced by the Strecker reaction into an amine and amide and complete deprotection, a small library of five-membered iminocyclitols consisting of 27 compounds was synthesized. A series of compounds obtained by reductive amination was first screened as potential inhibitors of glycosidases and glycosyltransferases. Among them, compounds carrying a C(10)-alkyl group showed marked enhancement of inhibitory activity against alpha-mannosidase at 10 microM concentration when compared with its parent compound and deoxymannojirimycin. Furthermore, compounds having the phenylethyl group showed an extremely strong inhibitory effect against alpha-galactosaminidase at a K(i) value of 29.4 nM. Compounds with an aminomethyl and amide group at the C-1' position of these two molecules showed a decrease in inhibitory activities. CONCLUSIONS: A combinatorial approach based on five-membered iminocyclitols with a galacto-configuration was exploited. The potential usefulness of the library as a source of inhibitors of glycoenzymes is clearly shown in this study.     

Systematic syntheses and inhibitory activities of bisubstrate-type inhibitors of sialyltransferases

Bisubstrate-type sialyltransferase inhibitors 1/2a-e, having CMP-NeuAc and N-acetyllactosamine (or lactose) moieties connected by an alkanedithiol linker, were synthesized systematically. A uniform synthetic strategy was adopted that consists of consecutive couplings of three components (N-acetyllactosamine or lactose, sialic acid, and CMP), followed by oxidation. Due to the sensitivity of the compounds under alkaline conditions, final deprotection required careful monitoring by (1)H NMR. The inhibitory activities of 1/2a-e toward ST6N and ST3N indicated that both the structure of the acceptor moiety and the distance between donor and acceptor moieties were important.     

Chemical constituents from the bark of bauhinia purpurea and their NO inhibitory activities

Abstract

Phytochemical studies led to the isolation of a new phenylpropanoid glucoside, named purpuroside (1), along with eight known compounds (2–9) from the bark of Bauhinia purpurea. The structure of the new compound was elucidated on the basis of its spectroscopic data. The absolute configuration of compound 2 was verified by X-ray diffraction analysis. Compounds 1, 2, 7, 8, and 9 inhibited NO production in mouse peritoneal macrophages with IC₅₀ values from 35.5 to 63.0?μM.     

Synthesis of bisubstrate and donor analogues of sialyltransferase and their inhibitory activities

[reaction: see text] Sialyltransferases (STs) are involved in the biosynthesis of glycoconjugates with important biological activities. Most STs utilize cytidine-5'-monophospho-N-acetylneuraminic acid (CMP-Neu5Ac) as a common donor substrate. A bisubstrate analogue containing the donor substrate (CMP-Neu5Ac mimic) and the acceptor substrate (galactose) was synthesized. Four donor analogues having the partial structure of the bisubstrate analogue were also synthesized to support study of the structure-activity relationship. Each analogue contains an ethylene group in place of the exocyclic anomeric oxygen of CMP-Neu5Ac. The bisubstrate analogue exhibited only weak inhibitory activity to rat recombinant alpha-2,3- and alpha-2,6-ST (IC(50) = 1.3, 2.4 mM). Conversion of the C-1 carboxylate of the Neu5Ac moiety to carboxyamide, hydroxymethyl, or methylene phosphate each resulted in a reduction in inhibitory activity. Among the synthesized analogues, cytidin-5'-yl sialylethylphosphonate (4) was the most potent inhibitor against rat recombinant alpha-2,3- and alpha-2,6-ST (IC(50) = 0.047, 0.34 mM).     

Synthesis and iNOS/nNOS inhibitory activities of new benzoylpyrazoline derivatives

A series of new Δ²-pyrazoline derivatives has been synthesized by means of a 1,3-dipolar-cycloaddition reaction. Ethyl 3-(5-methoxy-2-nitrobenzoyl)-Δ²-pyrazoline-5-carboxylate (5a) has been designed for the formation of the benzoylpyrazoline system present in these derivatives. Two synthetic routes have been utilized changing the starting products in the cycloaddition reaction. In both routes, the majority product obtained was only a Δ²-pyrazoline. The intermediate ethyl 1-acyl-3-(2-nitrobenzoyl-5-substituted)-Δ²-pyrazoline-5-carboxylate derivatives have been transformed into the final compounds by means of several chemical treatments. The compounds have been biologically evaluated as inhibitors of nitric oxide synthase (NOS), showing better affinity towards the inducible NOS isoform than versus neuronal NOS.     

Myeloperoxidase inhibitory and radical scavenging activities of flavones from Pterogyne nitens

Two new flavone glucosides, nitensosides A and B (1, 2), together with four known compounds, sorbifolin (3), sorbifolin 6-O-beta-glucopyranoside (4), pedalitin (5), and pedalitin 6-O-beta-glucopyranoside (6) were isolated from Pterogyne nitens. Their structures were elucidated from 1D and 2D NMR analysis, as well as by high resolution mass spectrometry. All the isolated flavones were evaluated for their myeloperoxidase (MPO) inhibitory activity. The most active compound, pedalitin, exhibited IC50 value of 3.75 nM on MPO. Additionally, the radical-scavenging capacity of flavones 1-6 was evaluated towards ABTS and DPPH radicals and compared to standard compounds quercetin and Trolox.     

Antioxidant and hyaluronidase inhibitory activities of diverse phenolics in Phyllanthus emblica

Fifty-eight phenolic compounds isolated from Phyllanthus emblica were screened and compared for their in vitro and in vivo antioxidant properties, as well as hyaluronidase (HAase) inhibitory activities. Among them, 20 compounds showed to be promising antioxidants due to the stronger scavenging activity in both DPPH radical and Danio rerio reactive oxygen species assays, while nine compounds were potential HAase inhibitors with 100-fold stronger activities than that of the positive control, DSCG. The structure activity relationship was discussed.     

Antioxidant and alpha-glucosidase inhibitory activities of isoflavonoids from the rhizomes of Ficus tikoua Bur

A new unique isoflavone derivatives with a cyclic-monoterpene-substituent, ficusin C (1), together with five known compounds (2–6), were isolated from the rhizomes of Ficus tikoua. Their structures were elucidated on the basis of spectroscopic data interpretation, mass spectrometric analysis and comparison with literature data of related compounds. Antioxidant and α-glucosidase inhibitory activities of these compounds were evaluated by 1,1-diphenyl-2-picryhydrazyl (DPPH) radical-scavenging assay and α-glucosidase inhibitory experiment, respectively.     

Chemical constituents of the aerial parts of Scutellaria lateriflora and their alpha-glucosidase inhibitory activities

MeOH extracts of 37 herbs were tested in screening experiments for rat intestinal alpha-glucosidase. The MeOH extract of the aerial parts of Scutellaria lateriflora L. (Lamiaceae) significantly inhibited sucrase and maltase activities, using sucrose and maltase as the substrates. Enzyme inhibition guided-fractionation of the MeOH extract of S. lateriflora resulted in the isolation of a new diterpene glucoside, deacetylajugarin-IV 18-O-beta-D-glucopyranoside (1), along with 20 known phenolics (2-21). The structures of 1-21 were elucidated on the basis of MS and NMR data analyses. Baicalein (4) and baicalin (10), a glycoside of 4, showed moderate sucrase inhibitory activities at IC50 values of 14.9 and 36.3 microM, respectively, whereas luteolin (3), acteoside (16), leucosceptoside A (18), and isoacteoside (20) showed weak inhibitory activities at IC50 values of 811, 522, 727, and 443 microM, respectively. This is the first report on mammalian alpha-glucosidase inhibitory activities of S. lateriflora extract and identification of the constituents responsible for the activities. Apigenin (2), luteolin (3), 6-methoxyluteolin 4'-methyl ether (6), isoscutellarin 8-O-beta-D-glucuronide (7), luteolin 7-O-beta-D-glucuronide (9), wogonin 7-O-beta-D-glucuronide methyl ester (12), eriodictyol (13), naringenin (14), naringenin 7-O-beta-D-glucuronide (15), jionoside D (17), leucosceptoside A (18), and (+)-syringaresinol 4'-O-beta-D-glucopyranoside (21) were isolated from this plant for the first time. The inhibitory properties of S. lateriflora extract against alpha-glucosidase provide a prospect for its antidiabetic usage.     

Pseudoamide-type pyrrolidine and pyrrolizidine glycomimetics and their inhibitory activities against glycosidases

Coupling reaction of (2R,3R,4R,5R)-2,5-hydroxymethyl-3,4-dihydroxypyrrolidine (DMDP) with isothiocyanates afforded the corresponding thiourea adducts, which were transformed into isourea-type bicyclic oxapyrrolizidine glycomimetics by mercury(II) oxide-assisted intramolecular sulfur displacement. Cyclic carbamate and thiocarbamate analogues were also prepared by direct carbonylation or thiocarbonylation of DMDP. Evaluation of the glycosidase inhibitory properties demonstrated that remarkable specificities in enzyme inhibition can be achieved upon modifications on the pseudoaglyconic side chain and on the nature of the sp(2)-hybridized endocyclic ring nitrogen.     

Polymer-like polyphenols of black tea and their lipase and amylase inhibitory activities

Lipase and amylase inhibitory activities of black tea were examined. After solvent partitioning of a black tea extract with the ethyl acetate and n-butanol, the two soluble fractions showed comparable inhibitory activities. Activity in the ethyl acetate fraction was mainly attributable to polyphenols with low-molecular weights, such as theaflavin gallates. On the other hand, the active substance in the n-butanol layer was ascertained to be a polymer-like substance. 1H- and 13C-NMR spectra showed signals arising from the flavan A-ring and galloyl groups, although signals due to flavan B-rings were not detected, suggesting that the polymer-like substances were generated by oxidative condensation of flavan B-rings, a result which was previously deduced from our results of in vitro catechin oxidation experiments. Enzymatic oxidation of epicatechin 3-O-gallate produced a similar polymer-like substance and suggested that condensation between a B-ring and galloyl groups was involved in the polymerization reaction.     

Synthesis of polyhydroxylated pyrrolizidine and indolizidine compounds and their glycosidase inhibitory activities

The synthesis of the natural product 3-epi-casuarine and two tricyclic ether bridged analogues, plus 7-deoxy-3,6-diepi-casuarine, 7-epi-australine, 1-epi-castanospermine and 1,6-diepi-castanospermine is described. The glycosidase inhibitory activities of these compounds, along with that of uniflorine A and other polyhydroxylated pyrrolizidines and indolizidines that we have published before, are reported.     

Evaluating use of ferricyanide-mediated respiration bioassays to quantify stimulatory and inhibitory effects on Escherichia coli populations

A number of recent studies have utilised ferricyanide as a respiratory mediator for microbial-based assays for determining water quality parameters such as biochemical oxygen demand (BOD) and toxicity. The majority of assays published to date obtain a result by determining the difference in ferrocyanide accumulation between a test sample and one or more control samples. However, a validation of the relationship between ferrocyanide accumulation and standard measures of cell density or viability has not yet been performed. To this end, a rapid microbially catalysed ferricyanide-mediated respiration (FM-RES) assay was compared with standard plate count (SPC) and spectrophotometer (OD₆₀₀) measurements on a growing batch culture of Escherichia coli. Good agreement was observed between all techniques, with predictable deviations noted in different phases of the growth curves. Standardised FM-RES assays showed excellent correlations with the SPC method under controlled conditions, indicating that short-term changes in microbial activity are due to a change in per-cell respiration, rather than changes in cell numbers. The FM-RES assay was then used to observe the changes in the respiration of E. coli induced by the addition of a glucose-glutamic acid (GGA) mixture, 3,5-dichlorophenol (3,5-DCP) and Ag⁺ in various combinations and concentrations. Stimulation of respiration was pronounced in the presence of GGA while both 3,5-DCP and, in particular, Ag⁺ demonstrated inhibitory respiratory effects. The results highlight the validity and suitability of ferricyanide-mediated respiration bioassays, with appropriate modification, to monitor either stimulatory effects on microbial populations, such as occurs with BOD, or inhibitory effects, such as occurs with toxicity assays.     

Conduramine F-1 epoxides: synthesis and their glycosidase inhibitory activities

Starting from (±)-7-oxanorbornenone ((±)-14), (±)-(1RS,2RS,3SR,6SR)-6-azidocyclohex-4-en-1,2,3-triol ((±)-24) and (±)-(1RS,2RS,3SR,6RS)-6-azidocyclohex-4-en-1,2,3-triol ((±)-26) were obtained. Epoxidation of the latter cyclohexene derivative gave two epoxides (±)-30 and (±)-31 that were converted into (±)-conduramine F-1 epoxides (±)-10 and (±)-11 and N-substituted derivatives (±)-12 and (±)-13. Compound (±)-(1RS,2SR,3RS,4SR,5RS,6SR)-5-({[4-(trifluoromethyl)phenyl]methyl}amino)-7-oxabicyclo[4.1.0]heptane-2,3,4-triol ((±)-12c) is a good, non-competitive inhibitor of β-xylosidase from Aspergillus niger (K_i=2.2 μM), and (±)-(1RS,2RS,3SR,4RS,5SR,6SR)-5-{[(biphenyl-4-yl)methyl]amino}-7-oxabicyclo[4.1.0]heptane-2,3,4-triol ((±)-13d) is a good inhibitor of α-glucosidase from brewer's yeast (K_i=2.8 μM, non-competitive).     

New lignans from Kadsura coccinea and their nitric oxide inhibitory activities

In vitro anti-allergic screening of medicinal herbal extracts revealed that the chloroform extract of the rhizoma of Kadsura coccinea inhibited nitric oxide (NO) production in a lipopolysaccharide (LPS) and recombinant mouse interferon-gamma (IFN-gamma) activated murine macrophage like cell line RAW 264.7. Further fractionation of the chloroform extract led to the isolation of three new lignans, including two dibenzocyclooctadiene lignans and one arylnaphthalene lignan, together with other three known dibenzocyclooctadiene lignans. This is the first report of NO production inhibitory activity of Kadsura coccinea and first report about the isolation of arylnaphthalene lignan from K. coccinea.     

Synthesis and aldose reductase inhibitory activities of benzyl 2-oxazolecarbamate analogues.

Various analogues of benzyl 5-phenyl-2-oxazolecarbamate (1a) were synthesized, and the structure-activity relationship of these analogues as aldose reductase inhibitor was studied. The carbamate group was necessary for the inhibitory activity. The introduction of an alkyl group at the C-4 position of 1a enhanced the inhibitory activity, however, the N-carboxymethyl group on the carbamate moiety counteracted to a hydrophobic interaction between the alkyl group at the C-4 position and the enzyme molecule.     

Flavonoids from Daphne aurantiaca and their inhibitory activities against nitric oxide production

Chemical examination of the methanolic extract from the stem bark of Daphne aurantiaca led to the isolation of three new flavonoids (1-3), and 29 known flavonoids. All 32 compounds were isolated for the first time from Daphne aurantiaca. The isolates were tested for inhibitory activities against lipopolysaccharide (LPS)-induced nitric oxide (NO) production in RAW 264.7 macrophages. Compounds 21 and 24 showed potent inhibitory activities against the production of NO with IC?? values of 0.006 and 0.076 μM, respectively.