Novel alpha-glucosidase inhibitors with a tetrachlorophthalimide skeleton

Borylated 2,3,4,5-Tetrachlorophthalimide and Their 2,3,4,5-Tetrachlorobenzamide Analogues: Synthesis, Their Glycosidase Inhibition and Anticancer Properties in View to Boron Neutron Capture Therapy

Tetrachlorinated phthalimide analogues bearing a boron-pinacolate ester group were synthesised via two synthetic routes and evaluated in their glycosidase modulating and anticancer properties, with a view to use them in boron neutron capture therapy (BNCT), a promising radiation type for cancer, as this therapy does little damage to biological tissue. An unexpected decarbonylation/decarboxylation to five 2,3,4,5-tetrachlorobenzamides was observed and confirmed by X-ray crystallography studies, thus, giving access to a family of borylated 2,3,4,5-tetrachlorobenzamides. Biological evaluation showed the benzamide drugs to possess good to weak potencies (74.7-870 μM) in the inhibition of glycosidases, and to have good to moderate selectivity in the inhibition of a panel of 18 glycosidases. Furthermore, in the inhibition of selected glycosidases, there is a core subset of three animal glycosidases, which is always inhibited (rat intestinal maltase α-glucosidase, bovine liver β-glucosidase and β-galactosidase). This could indicate the involvement of the boron atom in the binding. These glycosidases are targeted for the management of diabetes, viral infections (via a broad-spectrum approach) and lysosomal storage disorders. Assays against cancer cell lines revealed potency in growth inhibition for three molecules, and selectivity for one of these molecules, with the growth of the normal cell line MCF10A not being affected by this compound. One of these molecules showed both potency and selectivity; thus, it is a candidate for further study in this area. This paper provides numerous novel aspects, including expedited access to borylated 2,3,4,5-tetrachlorophthalimides and to 2,3,4,5-tetrachlorobenzamides. The latter constitutes a novel family of glycosidase modulating drugs. Furthermore, a greener synthetic access to such structures is described.

Ligand compatibility of salacinol-type α-glucosidase inhibitors toward the GH31 family

We show that salacinol-type α-glucosidase inhibitors are ligand-compatible with the GH 31 family. Salacinol and its 3′-O-benzylated analogs inhibit human lysosomal α-glucosidase at submicromolar levels. Simple structure-activity relationship studies reveal that the salacinol side-chain stereochemistry significantly influences binding to GH31 α-glucosidases.

Salacinol-type α-glucosidase inhibitors are ligand-compatible with the GH 31 family. Salacinol and its 3′-O-benzylated analogs inhibit human lysosomal α-glucosidase at submicromolar levels.

Organocatalyzed Synthesis of Highly Functionalized Phthalimides via Diels-Alder Reaction Employing Two Dienophiles

An efficient and facile protocol for the synthesis of biologically and pharmaceutically important phthalimides is developed by l-proline-catalyzed reaction between two dienophiles of α,β-unsaturated aldehydes and maleimides. The reaction involves an efficient benzannulation that proceeds via a formal [4 + 2] cycloaddition of azadiene intermediates generated in situ from enals and N-substituted maleimides. This protocol provides a variety of functionalized phthalimide derivatives, including a potent COX-2 enzyme inhibitor.

Design and synthesis of 4,5-diphenyl-imidazol-1,2,3-triazole hybrids as new anti-diabetic agents: in vitro α-glucosidase inhibition, kinetic and docking studies

Fourteen novel 4,5-diphenyl-imidazol-1,2,3-triazole hybrids 8a-n were synthesized with good yields by performing click reaction between the 4,5-diphenyl-2-(prop-2-yn-1-ylthio)-1H-imidazole and various benzyl azides. The synthesized compounds 8a-n were evaluated against yeast α-glucosidase, and all these compounds exhibited excellent inhibitory activity (IC₅₀ values in the range of 85.6 ± 0.4-231.4 ± 1.0 μM), even much more potent than standard drug acarbose (IC₅₀ = 750.0 μM). Among them, 4,5-diphenyl-imidazol-1,2,3-triazoles possessing 2-chloro and 2-bromo-benzyl moieties (compounds 8g and 8i) demonstrated the most potent inhibitory activities toward α-glucosidase. The kinetic study of the compound 8g revealed that this compound inhibited α-glucosidase in a competitive mode. Furthermore, docking calculations of these compounds were performed to predict the interaction mode of the synthesized compounds in the active site of α-glucosidase. A novel series of 4,5-diphenyl-imidazol-1,2,3-triazole hybrids 8a-n was synthesized with good yields by performing click reaction between the 4,5-diphenyl-2-(prop-2-yn-1-ylthio)-1Himidazole and various benzyl azides. The synthesized compounds 8a-n were evaluated against yeast α-glucosidase and all these compounds exhibited excellent inhibitory activity (IC50 values in the range of 85.6 ± 0.4-231.4 ± 1.0 μM), even much more potent than standard drug acarbose (IC50 = 750.0 μM).

Brevipsidone, a New Depsidone and Other α-Glucosidase Inhibitors from Garcinia Brevipedicellata (Clusiaceae)

Brevipsidone (1), a new depsidone was isolated from the methanol extract of the stem bark of Garcinia brevipedicellata together with known damnacanthal (2), pilloin (3), scopoletin (4). The structure of the new compound was determined by analysis of spectroscopic data. Compounds 1–4 were evaluated for their α-glucosidase inhibition effect and showed significant inhibitory activity.

Novel pyridine-2,4,6-tricarbohydrazide thiourea compounds as small key organic molecules for the potential treatment of type-2 diabetes mellitus: In vitro studies against yeast α- and β-glucosidase and in silico molecular modeling

A range of novel pyridine-2,4,6-tricarbohydrazide thiourea compounds (4a-i) were synthesized in good to excellent yields (63-92%). The enzyme inhibitory potentials of these compounds were investigated against α- and β-glucosidases because these enzymes play a crucial role in treating type-2 diabetes mellitus (T2DM). As compared to the reference compound acarbose (IC₅₀ 38.22 ± 0.12 μM), compounds 4i (IC₅₀ 25.49 ± 0.67 μM), 4f (IC₅₀ 28.91 ± 0.43 μM), 4h (IC₅₀ 30.66 ± 0.52 μM), and 4e (IC₅₀ 35.01 ± 0.45 μM) delivered better inhibition against α-glucosidase and were quite inactive/completely inactive against β-glucosidase. The structure-activity relationship of these compounds was developed and elaborated with the help of molecular docking studies.

New α-glucosidase inhibitors from marine algae-derived Streptomyces sp. OUCMDZ-3434

Wailupemycins H (1) and I (2) with a new skeleton coupled two 6-(2-phenylnaphthalene-1-yl)pyrane-2-one nuclei to a –CH₂– linkage were identified from the culture of Streptomyces sp. OUCMDZ-3434 associated with the marine algae, Enteromorpha prolifera. Compounds 1 and 2 are two new α-glucosidase inhibitors with the K_i/IC₅₀ values of 16.8/19.7 and 6.0/8.3 μM, respectively. In addition, the absolute configurations of wailupemycins D (3) and E (4) are also resolved in this paper for the first time.

Synthesis of novel flavone hydrazones: in-vitro evaluation of α-glucosidase inhibition, QSAR analysis and docking studies

Thirty derivatives of flavone hydrazone (5-34) had been synthesized through a five-step reaction and screened for their α-glucosidase inhibition activity. Chalcone 1 was synthesized through aldol condensation then subjected through oxidative cyclization, esterification, and condensation reaction to afford the final products. The result for baker's yeast α-glucosidase (EC 3.2.1.20) inhibition assay showed that all compounds are active with reference to the IC50 value of the acarbose (standard drug) except for compound 3. Increase in activity observed for compounds 2 to 34 clearly highlights the importance of flavone, hydrazide and hydrazone linkage in suppressing the activity of α-glucosidase. Additional functional group on N-benzylidene moiety further enhances the activity significantly. Compound 5 (15.4 ± 0.22 μM), a 2,4,6-trihydroxy substituted compound, is the most active compound in the series. Other compounds which were found to be active are those having chlorine, fluorine, and nitro substituents. Compounds with methoxy, pyridine, and methyl substituents are weakly active. Further studies showed that they are not active in inhibiting histone deacetylase activity and do not possess any cytotoxic properties. QSAR model was being developed to further identify the structural requirements contributing to the activity. Using Discovery Studio (DS) 2.5, various 2D descriptors were being used to develop the model. The QSAR model is able to predict the pIC50 and could be used as a prediction tool for compounds having the same skeletal framework. Molecular docking was done for all compounds using homology model of α-glucosidase to identify important binding modes responsible for inhibition activity.

Organocatalyzed solvent free an efficient novel synthesis of 2,4,5-trisubstituted imidazoles for α-glucosidase inhibition to treat diabetes

A new and efficient solvent free synthesis of 2,4,5-trisubstituted imidazoles (3a-3j) was achieved by N-acetyl glycine (NAG) catalyzed three components condensation of aldehydes, benzil and ammonium acetate. Our synthetic methodology accommodated a range of various substituted alkyl and aryl aldehydes. Evaluation of α-glucosidase inhibitory activity of these imidazole derivatives revealed that most of them presented good α-glucosidase inhibition at low micro-molar concentrations. Among the synthesized compounds, compound 3c, bearing the ortho-hydroxy phenyl substituent at position 2 displayed the highest inhibitory activity with an IC50 value 74.32±0.59 μM. In silico molecular docking for all compounds and computational studies of the most active compound 3c were also performed.

Synthesis of novel indenoquinoxaline derivatives as potent α-glucosidase inhibitors

A series of new N-(11H-Indeno[1,2-b]quinoxalin-11-ylidene)benzohydrazide derivatives (3a-3p) were synthesized and evaluated for their α-glucosidase inhibitory activity. The synthesized compounds 3d, 3f, 3g, 3k, 3n, 3p and 4 showed significant α-glucosidase inhibitory activity as compared to acrabose, a standard drug used to treat type II diabetes. Structures of the synthesized compounds were determined by using FT-IR, (1)H NMR, (13)C NMR, mass spectrometry and elemental analysis techniques.

Novel α-Glucosidase Activator from Pulicaria undulata

A new ent –kaurane type diterpene glucoside, pulicarside (1), together with three known terpenoids, paniculoside IV (2, diterpene), ent–16, 17-dihydroxy-(-)-kauran-19–oic acid (3, diterpene), and 2α–hydroxy alantolactone (4, sesquiterpene) have been isolated from Pulicaria undulata L. Their structures were determined with the help of spectral studies. Pulicarside (1) showed α-glucosidase activator activity, whereas its hydrolyzed product ent-16, 17-dihydroxy-(-)-kauran-19-oic acid (3) exhibited strong α-glucosidase inhibitory activity. Paniculoside IV (2) also shows high inhibitory potency compared with the standard drug acarbose.

A new series of N2-substituted-5-(p-toluenesulfonylamino)phthalimide analogues as α-glucosidase inhibitors

Several members of a new family of non-sugar-type α-glycosidase inhibitors, bearing a 5-(p-toluenesulfonylamino)phthalimide moiety and various substituent at the N2 position, were synthesized and their activities were investigated. The newly synthesized compounds displayed different inhibition profile towards yeast α-glycosidase and rat intestinal α-glycosidase. Almost all the compounds had strong inhibitory activities against yeast α-glycosidase. Regarding rat intestinal α-glycosidase, only analogs with N2-aromatic substituents displayed varying degrees of inhibitory activities on rat intestinal maltase and lactase and nearly all compounds showed no inhibition against rat intestinal α-amylase. Structure-activity relationship studies indicated that 5-(p-toluenesulfonylamino)phthalimide moiety is a favorable scaffold to exert the α-glucosidase inhibitory activity and substituents at the N2 position have considerable influence on the efficacy of the inhibition activities.

Inhibition of monoamine oxidase by C5-substituted phthalimide analogues

Literature reports that isatin as well as C5- and C6-substituted isatin analogues are reversible inhibitors of human monoamine oxidase (MAO) A and B. In general, C5- and C6-substitution of isatin leads to enhanced binding affinity to both MAO isozymes compared to isatin and in most instances result in selective binding to the MAO-B isoform. Crystallographic and modeling studies suggest that the isatin ring binds to the substrate cavities of MAO-A and -B and is stabilized by hydrogen bond interactions between the NH and the C2 carbonyl oxygen of the dioxoindolyl moiety and water molecules present in the substrate cavities of MAO-A and -B. Based on these observations and the close structural resemblances between isatin and its phthalimide isomer, a series of phthalimide analogues were synthesized and evaluated as MAO inhibitors. While phthalimide and N-aryl-substituted phthalimides were found to be weak MAO inhibitors, phthalimide homologues containing C5 substituents were potent reversible inhibitors of recombinant human MAO-B with IC(50) values ranging from 0.007 to 2.5 μM and moderately potent reversible inhibitors of recombinant human MAO-A with IC(50) values ranging from 0.22 to 9.0 μM. By employing molecular docking the importance of hydrogen bonding between the active sites of MAO-A and -B and the phthalimide inhibitors are highlighted.

Triterpenoids from the roots of Sanguisorba tenuifolia var. Alba

The ethyl acetate soluble fraction from the roots of Sanguisorba tenuifolia was found to have a hypoglucemic effect in alloxan-induced diabetic rats. Two new triterpenoids, identified as 2-oxo-3β,19α-dihydroxyolean-12-en-28-oic acid β-D-gluco-pyranosyl ester (1) and 2α,19α-dihydroxy-3-oxo-12-ursen-28-oic acid β-D-glucopyranosyl ester (4) were isolated from this fraction, along with thirteen known triterpenoids. Their structures were elucidated by chemical and spectroscopic methods. All these compounds demonstrated inhibitory activities against α-glucosidase with IC₅₀ values in the 0.62-3.62 mM range.

Kaurane-type diterpenoids from Chromoleana odorata, their X-ray diffraction studies and potent α-glucosidase inhibition of 16-kauren-19-oic acid

A new diterpenoid, 15-angeloyloxy-16,17-epoxy-19-kauronic acid (1), along with five known metabolites, 16-kauren-19-oic acid (2), 6'-hydroxy-2',3',4,4'-tetramethoxychalcone (3), isosakuranetin (4), acacetin (5), and kaempferide (6) was isolated from the organic extracts of the roots of Chromoleana odorata. Their structures were determined by spectroscopic evidences. The structures of 1 and 2 were further confirmed by single-crystal X-ray diffraction studies. Compound 2 exhibited significant α-glucosidase inhibitory and antibacterial activities against Escherichia coli and Bacillus subtilis.

Separation of alpha-glucosidase-inhibitory and liver X receptor-antagonistic activities of phenethylphenyl phthalimide analogs and generation of LXRalpha-selective antagonists

Liver X receptor (LXR) alpha/beta dual agonists are candidate medicaments for the treatment of metabolic syndrome, because their biological actions include increasing cholesterol efflux mediated by LXRbeta. However, their clinical application is currently limited by their enhancing effect on triglyceride (TG) synthesis mediated by LXRalpha. Combination of an LXRalpha-selective antagonist with an LXRalpha/beta dual agonist may overcome this disadvantage. In the present work, structural development studies of phenethylphenyl phthalimide 9, which possesses LXRalpha/beta dual-antagonistic activity and alpha-glucosidase-inhibitory activity, led to the LXRalpha-selective antagonist 23f. Specific alpha-glucosidase inhibitors were also obtained.

In vitro anticancer property of a novel thalidomide analogue through inhibition of NF-kappaB activation in HL-60 cells

AIM

To investigate the anticancer property and possible mechanism of action of a novel sugar-substituted thalidomide derivative (STA-35) on HL-60 cells in vitro.

METHODS

TNF-alpha-induced NF-kappaB activation was determined using a reporter gene assay. The MTT assay was used to measure cytotoxicity of the compound. The appearance of apoptotic Sub-G1 cells was detected by flow cytometry analysis. PARP cleavage and protein expression of NF-kappaB p65 and its inhibitor IkappaB were viewed by Western blotting.

RESULTS

TA-35 (1-20 micromol/L) suppressed TNF-alpha-induced NF-kappaB activation in transfected cells (HEK293/pNiFty-SEAP) in a dose- (1-20 micromol/L) and time-dependent (0-48 h) manner. It was also shown that STA-35 exerted a dose-dependent inhibitory effect on HL-60 cell proliferation with an IC(50) value of 9.05 micromol/L. In addition, STA-35 induced apoptosis in HL-60 cells, as indicated by the appearance of a Sub-G1 peak in the cell cycle distribution, as well as poly ADP-ribose polymerase (PARP) cleavage. Subsequently, both NF-kappaB p65 and its inhibitor IkappaB gradually accumulated in cytoplasmic extracts in a dose- and time-dependent manner, indicating the blockage of NF-kappaB translocation induced by TNF-alpha from the cytoplasm to the nucleus.

CONCLUSION

A novel sugar-substituted thalidomide derivative, STA-35, is potent toward HL-60 cells in vitro and induces apoptosis by the suppression of NF-kappaB activation.

Novel easily accessible glucosidase inhibitors: 4-hydroxy-5-alkoxy-1,2-cyclohexanedicarboxylic acids

Glycosidases are very important enzymes involved in a variety of biochemical processes with a special importance to biotechnology, food industry, and pharmacology. Novel structurally simple inhibitors derived from cyclohexane-1,2-dicarboxylic acids were synthesized and tested against several fungal glycosidases from Aspergillus oryzae and Penicilliumcanescens. The presence of at least two carboxylic groups and one hydroxy group was essential for efficient inhibition. Significant selective inhibition was observed for alpha- and beta-glucosidases, the magnitude of which depended on the configuration of substituents; inhibition increased for beta-glucosidase by lengthening the alkoxy group of the inhibitor.

alpha-Glucosidase inhibitory activity of triterpenoids from Cichorium intybus

Two new triterpenoids, 18alpha,19beta-20(30)-taraxasten-3beta,21alpha-diol (cichoridiol) (1) and 17-epi-methyl-6-hydroxyangolensate (intybusoloid) (2), were obtained from the methanolic extract of seeds of Cichorium intybus along with 11 known compounds, lupeol (3), friedelin (4), beta-sitosterol (5), stigmasterol (6), betulinic acid (7), betulin (8), betulinaldehyde (9), syringic acid (10), vanillic acid (11) 6,7-dihydroxycoumarin (12), and methyl-alpha-D-galactopyranoside (13). Compounds 1, 1a, and 11 showed a good alpha-glucosidase inhibitory activity.

Bioactive aristolactams from Piper umbellatum

Four alkaloids named piperumbellactams A-D (1-4) were isolated from branches of Piper umbellatum together with known N-hydroxyaristolam II (5), N-p-coumaroyl tyramine (6), 4-nerolidylcatechol (7), N-trans-feruloyltyramine, E-3-(3,4-dihydroxyphenyl)-N-2-[4-hydroxyphenylethyl]-2-propenamide, beta-amyrin, friedelin, apigenin 8-C-neohesperidoside, acacetin 6-C-beta-d-glucopyranoside, beta-sitosterol, its 3-O-beta-d-glucopyranoside and its 3-O-beta-d-[6'-dodecanoyl]-glucopyranoside. Glycosidase inhibition, antioxidant and antifungal activities of these compounds were evaluated. Compounds 1-3 showed moderate alpha-glucosidase enzyme inhibition with IC50 values 98.07+/-0.44, 43.80+/-0.56 and 29.64+/-0.46, respectively. In DPPH radical scavenging assay, compounds 2, 3 and 6 showed potent inhibitory activity while compounds 4, 5 and 7 showed potent antifungal activity.

Alpha-glucosidase inhibitors from Millettia conraui

A new geranylated isoflavone, 7-O-geranyl-6-methoxypseudobaptigenin (1) was isolated from the stem barks of Millettia conraui, along with known compounds 5-methoxydurmillone (2), conrauinone A (3), beta-amyrine (4), sitosterol (5), 3-O-beta-D-glucopyranosyl sitosterol (6) and n-docosanol (7). Compounds 1 and 4 showed a significant alpha-glucosidase inhibitory activity. The structures of the compounds were determined by analysis of their spectroscopic data.

Liver X receptor antagonists with a phthalimide skeleton derived from thalidomide-related glucosidase inhibitors

Alpha-glucosidase inhibitors with a chlorinated phthalimide or a thiophthalimide skeleton, derived from thalidomide, were found to possess liver X receptor (LXR) antagonistic activity. Novel LXR antagonists with a 2'-substituted phenylphthalimide skeleton were obtained by structural development of glucosidase inhibitors derived from thalidomide.