Hydroxamate, a key pharmacophore exhibiting a wide range of biological activities

Condition-Controlled O-Acylation and N-O Bond Reduction of Hydroximic Acids with Thioacetic Acid

Condition-dependent transformations between hydroximic acids and thioacetic acid were achieved. Using NH₄HCO₃ in the ethanol solvent, efficient N-O bond cleavage of hydroxamic acids occurred to afford primary amides with high functional group compatibility. The reaction was switched to O-acylation when NEt₃ and H₂O were used as the base and solvent, respectively. These facile transformations could be scaled up to the gram level smoothly. Preliminary mechanistic studies suggested that the N-O bond cleavage involves a cascade process of acylation/reduction.

Visible-Light Mediated Carbamoylation of Nitrones under a Continuous Flow Regime

Herein, we report a rapid and scalable continuous-flow photocatalytic approach for the carbamoylation of nitrones. This protocol makes use of readily available 4-amido-1,4 dihydropyridines as carbamoyl radical precursors. The scope of this transformation exhibits high compatibility with complex structures containing amino acids, peptides, and glycosides. Importantly, the developed method allows a photocatalytic synthetic strategy in combination with flow conditions, maximizing the potential and efficiency for the synthesis of valuable α-(N-hydroxy)amino amides.

Iron Chelators, Such as Deferasirox, When Combined With Hydroxyurea, Provide an Additional Benefit of Iron Chelation in Patients Receiving Chronic Transfusion Therapy

Red blood cell (RBC) transfusions have been established as one of the primary therapies in treating sickle cell anemia. However, they are not free of side effects, with overloading the body with iron being one of the most important. Iron chelation therapy greatly reduces the iron load of the body. In addition, hydroxyurea (HU), an oral chemotherapeutic drug also has a significant role in the treatment of the disease with beneficial effects on many of the clinical problems that arise, mainly in reducing painful crises. The aim of this study was to investigate the effect of synergistic transfusion therapy and HU on the response to deferasirox (DFX) chelation therapy. Eighteen patients with sickle cell disease were divided into two groups based on their treatment, either with simple transfusions and DFX or with a combination of transfusion therapy, DFX and HU, and were evaluated with magnetic resonance imaging (MRI) for liver iron concentration (LIC) and biochemistry. All patients completed the study. The results of the study showed improvement in serum ferritin (FER) levels and LIC after 12 months of therapy in both groups, especially in the group receiving the combination therapy with HU. In addition, there was a noteworthy improvement in serum glutamic-oxaloacetic transaminase (SGOT), serum glutamic pyruvic transaminase (SGPT) and lactate dehydrogenase (LDH) levels with serum creatinine (Cr) levels remaining stable during the study in both groups. Hydroxyurea, when combined with iron chelators such as DFX, provides an additional benefit of iron chelation in patients receiving chronic transfusion therapy.

Asymmetric hydrogenation of TIPS-protected oximes with chiral boranes

An enantioselective metal-free hydrogenation of TIPS-protected oximes has been successfully realized for the first time by using chiral borane catalysts derived from chiral dienes and Piers' borane. A variety of hydroxylamine derivatives were afforded in 84-99% yields with 33-68% ees.

Development of effective biotransformation process for benzohydroxamic acid production using Bacillus smithii IIIMB2907

The present study entails the usefulness of thermophilic amidase-producing bacterium in the biotransformation of benzamide to benzohydroxamic acid (BHA). A bacterium Bacillus smithii IIIMB2907 was isolated from a soil sample collected from hot springs of Manikaran, Himachal Pradesh, India. The whole cells of the bacterium displayed versatile substrate specificity by exhibiting significant activity with a diverse range of amides. In addition, amidase from thermophilic bacterium was induced by adding Ɛ-caprolactam in the mineral base media. The optimum temperature and pH of acyltransferase activity of amidase enzyme were found to be 50 °C and 7.0, respectively. Interestingly, half-life (t _1/2) of this enzyme was 17.37 h at 50 °C. Bench-scale production and purification of BHA was carried out at optimized conditions which resulted in the recovery of 64% BHA with a purity of 96%. Owing to this, the reported process in the present study can be considered of immense industrial significance for the production of BHA.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13205-022-03109-2.

Diversity in the Interaction of Amino Acid- and Peptide-Based Hydroxamic Acids with Some Platinum Group Metals in Solution

Complexes that incorporate both ligand(s) and metal(s) exhibiting cytotoxic activity can especially be interesting to develop multifunctional drug molecules with desired activities. In this review, the limited number of solution results collected in our laboratory on the complexes of Pd(II) and two other platinum group metals—the half-sandwich type, [(η⁶-p-cym)Ru(H₂O)₃]²⁺, and [(η⁵-Cp*)Rh(H₂O)₃]²⁺—with hydroxamic acid derivatives of three amino acids, two imidazole analogues, and four small peptides are summarized and evaluated. Unlike the limited number of coordination sites of these metal ions (four and three for Pd(II) and the organometallic cations, respectively), the ligands discussed here offer a relatively high number of donor atoms as well as variation in their position within the ligands, resulting in a large versatility of the likely coordination modes. The review, besides presenting the solution equilibrium results, also discusses the main factors, such as (N,N) versus (O,O) chelate; size of chelate; amino-N versus imidazole-N; primary versus secondary hydroxamic function; differences between hydrolytic ability of the metal ions studied; and hydrolysis of the coordinated peptide hydroxamic acids in their Pd(II) complexes, which all determine the coordination modes present in the complexes formed in measurable concentrations in these systems. The options for the quantitative evaluation of metal binding effectivity and selectivity of the various ligands and the comparison with each other by using solution equilibrium data are also discussed.

Iron-catalyzed regioselective synthesis of (E)-vinyl sulfones mediated by unprotected hydroxylamines

An Fe-catalyzed unprotected hydroxylamine mediated Heck-type coupling between sulfinic acids and alkenes furnished structurally important (E)-vinyl sulfones with moderate to good yields, high atom-economy and regioselectivity.

Catalytic Reduction of Oximes to Hydroxylamines: Current Methods, Challenges and Opportunities

Catalytic reduction of oximes represents a direct efficient approach to synthesize valuable hydroxylamine derivatives. However this transformation presents significant challenges: oximes are hard to reduce and, if reactive, reductive cleavage of the weak N−O bond often leads to primary amine side products. The first suitable systems involved the use of platinum‐based heterogeneous catalysts with hydrogen as reductant and stoichiometric amounts of a strong Brønsted acid. More recently metal‐free and transition‐metal‐based homogeneous catalysts have been developed, which display the highest turnovers (up to 4000). In the asymmetric variants, the E/Z‐geometry of the oxime double bond affects significantly the stereoselectivity, sometimes requiring extra synthetic efforts in substrate preparation. This minireview provides an overview of the advances and limitations in catalytic oxime to hydroxylamine reduction. Emphasis is put on highlighting and comparing the practical aspects of the existing methods, such as their reaction conditions and substrate scope. Additionally, future directions for improving this young research area are suggested.

Gatorbulin-1, a distinct cyclodepsipeptide chemotype, targets a seventh tubulin pharmacological site

Tubulin-targeted chemotherapy has proven to be a successful and wide spectrum strategy against solid and liquid malignancies. Therefore, new ways to modulate this essential protein could lead to new antitumoral pharmacological approaches. Currently known tubulin agents bind to six distinct sites at α/β-tubulin either promoting microtubule stabilization or depolymerization. We have discovered a seventh binding site at the tubulin intradimer interface where a novel microtubule-destabilizing cyclodepsipeptide, termed gatorbulin-1 (GB1), binds. GB1 has a unique chemotype produced by a marine cyanobacterium. We have elucidated this dual, chemical and mechanistic, novelty through multidimensional characterization, starting with bioactivity-guided natural product isolation and multinuclei NMR-based structure determination, revealing the modified pentapeptide with a functionally critical hydroxamate group; and validation by total synthesis. We have investigated the pharmacology using isogenic cancer cell screening, cellular profiling, and complementary phenotypic assays, and unveiled the underlying molecular mechanism by in vitro biochemical studies and high-resolution structural determination of the α/β-tubulin-GB1 complex.

Iridium-Catalyzed Acid-Assisted Hydrogenation of Oximes to Hydroxylamines

We found that cyclometalated cyclopentadienyl iridium(III) complexes are uniquely efficient catalysts in homogeneous hydrogenation of oximes to hydroxylamine products. A stable iridium C,N-chelation is crucial, with alkoxy-substituted aryl ketimine ligands providing the best catalytic performance. Several Ir-complexes were mapped by X-ray crystal analysis in order to collect steric parameters that might guide a rational design of even more active catalysts. A broad range of oximes and oxime ethers were activated with stoichiometric amounts of methanesulfonic acid and reduced at room temperature, remarkably without cleavage of the fragile N-O bond. The exquisite functional group compatibility of our hydrogenation system was further demonstrated by additive tests. Experimental mechanistic investigations support an ionic hydrogenation platform, and suggest a role for the Brønsted acid beyond a proton source. Our studies provide deep understanding of this novel acidic hydrogenation and may facilitate its improvement and application to other challenging substrates.

Characterization of a broadly specific cadaverine N-hydroxylase involved in desferrioxamine B biosynthesis in Streptomyces sviceus

N-hydroxylating flavin-dependent monooxygenases (FMOs) are involved in the biosynthesis of hydroxamate siderophores, playing a key role in microbial virulence. Herein, we report the first structural and kinetic characterization of a novel alkyl diamine N-hydroxylase DesB from Streptomyces sviceus (SsDesB). This enzyme catalyzes the first committed step in the biosynthesis of desferrioxamine B, a clinical drug used to treat iron overload disorders. X-ray crystal structures of the SsDesB holoenzyme with FAD and the ternary complex with bound NADP+ were solved at 2.86 Å and 2.37 Å resolution, respectively, providing a structural view of the active site environment. SsDesB crystallized as a tetramer and the structure of the individual protomers closely resembles the structures of homologous N-hydroxylating FMOs from Erwinia amylovora (DfoA), Pseudomonas aeruginosa (PvdA), and Aspergillus fumigatus (SidA). Using NADPH oxidation, oxygen consumption, and product formation assays, kinetic parameters were determined for various substrates with SsDesB. SsDesB exhibited typical saturation kinetics with substrate inhibition at high concentrations of NAD(P)H as well as cadaverine. The apparent kcat values for NADPH in steady-state NADPH oxidation and oxygen consumption assays were 0.28 ± 0.01 s-1 and 0.24 ± 0.01 s-1, respectively. However, in product formation assays used to measure the rate of N-hydroxylation, the apparent kcat for NADPH (0.034 ± 0.008 s-1) was almost 10-fold lower under saturating FAD and cadaverine concentrations, reflecting an uncoupled reaction, and the apparent NADPH KM was 33 ± 24 μM. Under saturating FAD and NADPH concentrations, the apparent kcat and KM for cadaverine in Csaky assays were 0.048 ± 0.004 s-1 and 19 ± 9 μM, respectively. SsDesB also N-hydroxylated putrescine, spermidine, and L-lysine substrates but not alkyl (di)amines that were branched or had fewer than four methylene units in an alkyl chain. These data demonstrate that SsDesB has wider substrate scope compared to other well-studied ornithine and lysine N-hydroxylases, making it an amenable biocatalyst for the production of desferrioxamine B, derivatives, and other N-substituted products.

Synthesis of Hydroxamic Acid Derivatives Using Blocked (Masked) O-Isocyanate Precursors

Hydroxamic acids are present in a several pharmaceuticals and agrochemicals. Synthetic strategies providing access to hydroxamic acid derivatives remain limited, typically requiring the use of nucleophilic hydroxylamine reagents. Herein, a synthesis of hydroxamates from unactivated carboxylic acids is reported making use of rare blocked (masked) O-substituted isocyanates. The applicability of this transformation was highlighted by targeting the synthesis of vorinostat and belinostat derivatives.

Fluorometric sensing of hydroxylamine in an aqueous medium utilizing a diphenyl imidazole-based probe

The detection of hydroxylamine in an aqueous medium is challenging due to its very similar chemical reactivity to its nearest competitors such as hydrazine hydrate and primary amines. Moreover, the detection of hydroxylamine at neutral pH adds further complexity to the sensing phenomenon due to its poor reactivity in a neutral aqueous medium. In this work, we have presented a diphenyl imidazole benzaldehyde (DIB) probe which demonstrates the detection of hydroxylamine (HA) in micromolar concentrations with high selectivity in 5% DMSO phosphate buffer solution at pH 7.4 via a fluorescence "turn-on" signal. The interaction of hydroxylamine with the probe has been comprehensively studied by using fluorescence spectroscopy, proton NMR, FTIR, ESI-mass spectrometry and DLS measurements. The experimental results were further corroborated with the DFT studies. These results could pave the way toward the development of molecular indicators for hydroxylamine in chemical and biological platforms.

Expanding the chemical diversity through microorganisms co-culture: Current status and outlook

Natural products (NPs) are considered as a cornerstone for the generation of bioactive leads in drug discovery programs. However, one of the major limitations of NP drug discovery program is "rediscovery" of known compounds, thereby hindering the rate of drug discovery efficiency. Therefore, in recent years, to overcome these limitations, a great deal of attention has been drawn towards understanding the role of microorganisms' co-culture in inducing novel chemical entities. Such induction could be related to activation of genes which might be silent or expressed at very low levels (below detection limit) in pure-strain cultures under normal laboratory conditions. In this review, chemical diversity of compounds isolated from microbial co-cultures, is discussed. For this purpose, chemodiversity has been represented as a chemical-structure network based on the "Tanimoto Structural Similarity Index". This highlights the huge structural diversity induced by microbial co-culture. In addition, the current trends in microbial co-culture research are highlighted. Finally, the current challenges (1 - induction monitoring, 2 - reproducibility, 3 - growth time effect and 4 - up-scaling for isolation purposes) are discussed. The information in this review will support researchers to design microbial co-culture strategies for future research efforts. In addition, guidelines for co-culture induction reporting are also provided to strengthen future reporting in this NP field.

WMJ-S-001, a Novel Aliphatic Hydroxamate-Based Compound, Suppresses Lymphangiogenesis Through p38mapk-p53-survivin Signaling Cascade

Background and purpose: Angiogenesis and lymphangiogenesis are major routes for metastatic spread of tumor cells. It thus represent the rational targets for therapeutic intervention of cancer. Recently, we showed that a novel aliphatic hydroxamate-based compound, WMJ-S-001, exhibits anti-angiogenic, anti-inflammatory and anti-tumor properties. However, whether WMJ-S-001 is capable of suppressing lymphangiogenesis remains unclear. We are thus interested in exploring WMJ-S-001's anti-lymphangiogenic mechanisms in lymphatic endothelial cell (LECs).

Experimental approach: WMJ-S-001's effects on LEC proliferation, migration and invasion, as well as signaling molecules activation were analyzed by immunoblotting, flow-cytometry, MTT, BrdU, migration and invasion assays. We performed tube formation assay to examine WMJ-S-001's ex vivo anti-lymphangiogenic effects.

Key results: WMJ-S-001 inhibited serum-induced cell proliferation, migration, invasion in murine LECs (SV-LECs). WMJ-S-001 reduced the mRNA and protein levels of survivin. Survivin siRNA significantly suppressed serum-induced SV-LEC invasion. WMJ-S-001 induced p53 phosphorylation and increased its reporter activities. In addition, WMJ-S-001 increased p53 binding to the promoter region of survivin, while Sp1 binding to the region was decreased. WMJ-S-001 induced p38 mitogen-activated protein kinase (p38MAPK) activation. p38MPAK signaling blockade significantly inhibited p53 phosphorylation and restored survivin reduction in WMJ-S-001-stimulated SV-LCEs. Furthermore, WMJ-S-001 induced survivin reduction and inhibited cell proliferation, invasion and tube formation of primary human LECs.

Conclusions and Implications: These observations indicate that WMJ-S-001 may suppress lymphatic endothelial remodeling and reduce lymphangiogenesis through p38MAPK-p53-survivin signaling. It also suggests that WMJ-S-001 is a potential lead compound in developing novel agents for the treatment of lymphangiogenesis-associated diseases and cancer.

Desferrioxamine biosynthesis: diverse hydroxamate assembly by substrate-tolerant acyl transferase DesC

Hydroxamate groups play key roles in the biological function of diverse natural products. Important examples include trichostatin A, which inhibits histone deacetylases via coordination of the active site zinc(II) ion with a hydroxamate group, and the desferrioxamines, which use three hydroxamate groups to chelate ferric iron. Desferrioxamine biosynthesis in Streptomyces species involves the DesD-catalysed condensation of various N-acylated derivatives of N-hydroxycadaverine with two molecules of N-succinyl-N-hydroxycadaverine to form a range of linear and macrocyclic tris-hydroxamates. However, the mechanism for assembly of the various N-acyl-N-hydroxycadaverine substrates of DesD from N-hydroxycadaverine has until now been unclear. Here we show that the desC gene of Streptomyces coelicolor encodes the acyl transferase responsible for this process. DesC catalyses the N-acylation of N-hydroxycadaverine with acetyl, succinyl and myristoyl-CoA, accounting for the diverse array of desferrioxamines produced by S. coelicolor The X-ray crystal structure of DesE, the ferrioxamine lipoprotein receptor, in complex with ferrioxamine B (which is derived from two units of N-succinyl-N-hydroxycadaverine and one of N-acetyl-N-hydroxycadaverine) was also determined. This showed that the acetyl group of ferrioxamine B is solvent exposed, suggesting that the corresponding acyl group in longer chain congeners can protrude from the binding pocket, providing insights into their likely function. This article is part of a discussion meeting issue 'Frontiers in epigenetic chemical biology'.This article is part of a discussion meeting issue 'Frontiers in epigenetic chemical biology'.

Inhibition of glioblastoma cell proliferation, invasion, and mechanism of action of a novel hydroxamic acid hybrid molecule

Glioblastoma multiforme is one of the most aggressive brain tumors and current therapies with temozolomide or suberoylanilide hydroxamic acid (SAHA, vorinostat) show considerable limitations. SAHA is a histone deacetylase (HDAC) inhibitor that can cause undesirable side effects due to the lack of selectivity. We show here properties of a novel hybrid molecule, sahaquine, which selectively inhibits cytoplasmic HDAC6 at nanomolar concentrations without markedly suppressing class I HDACs. Inhibition of HDAC6 leads to significant α-tubulin acetylation, thereby impairing cytoskeletal organization in glioblastoma cells. The primaquine moiety of sahaquine reduced the activity of P-glycoprotein, which contributes to glioblastoma multiforme drug resistance. We propose the mechanism of action of sahaquine to implicate HDAC6 inhibition together with suppression of epidermal growth factor receptor and downstream kinase activity, which are prominent therapeutic targets in glioblastoma multiforme. Sahaquine significantly reduces the viability and invasiveness of glioblastoma tumoroids, as well as brain tumor stem cells, which are key to tumor survival and recurrence. These effects are augmented with the combination of sahaquine with temozolomide, the natural compound quercetin or buthionine sulfoximine, an inhibitor of glutathione biosynthesis. Thus, a combination of agents disrupting glioblastoma and brain tumor stem cell homeostasis provides an effective anti–cancer intervention.

Identification of N-Hydroxycinnamamide analogues and their bio-evaluation against breast cancer cell lines

The present study demonstrates the identification of N-hydroxycinnamamide derivatives and their anticancer potential against human triple-negative breast cancer cell line MDA-MB‑231, MCF-7 and non-malignant origin cell line, HEK-293 (human embryonic kidney). MTT assay was studied with HEK-293 cell line. Anticancer potential of the N-hydroxycinnamamide derivatives were compared with marked drug Tamoxifen through in vitro study. The compound numbers 3b and 3h exhibit most potent activity against antagonistic breast cancer cells (MDA-MB-231) with IC₅₀13μM and 5μM respectively. Compound 3h promotes DNA fragmentation and induction of apoptosis. Furthermore, loss of mitochondrial membrane potential induced by compound 3h. The major mechanism of compound 3h for anti-breast cancer activity was probably initiation of reactive oxygen species (ROS) in cancer cells thereby persuading apoptotic cell deaths in cancer cells.

A Novel Hydroxamate-Based Compound WMJ-J-09 Causes Head and Neck Squamous Cell Carcinoma Cell Death via LKB1-AMPK-p38MAPK-p63-Survivin Cascade

Growing evidence shows that hydroxamate-based compounds exhibit broad-spectrum pharmacological properties including anti-tumor activity. However, the precise mechanisms underlying hydroxamate derivative-induced cancer cell death remain incomplete understood. In this study, we explored the anti-tumor mechanisms of a novel aliphatic hydroxamate-based compound, WMJ-J-09, in FaDu head and neck squamous cell carcinoma (HNSCC) cells. WMJ-J-09 induced G2/M cell cycle arrest and apoptosis in FaDu cells. These actions were associated with liver kinase B1 (LKB1), AMP-activated protein kinase (AMPK) and p38 mitogen-activated protein kinase (p38MAPK) activation, transcription factor p63 phosphorylation, as well as modulation of p21 and survivin. LKB1-AMPK-p38MAPK signaling blockade reduced WMJ-J-09’s enhancing effects in p63 phosphorylation, p21 elevation and survivin reduction. Moreover, WMJ-J-09 caused an increase in α-tubulin acetylation and interfered with microtubule assembly. Furthermore, WMJ-J-09 suppressed the growth of subcutaneous FaDu xenografts in vivo. Taken together, WMJ-J-09-induced FaDu cell death may involve LKB1-AMPK-p38MAPK-p63-survivin signaling cascade. HDACs inhibition and disruption of microtubule assembly may also contribute to WMJ-J-09’s actions in FaDu cells. This study suggests that WMJ-J-09 may be a potential lead compound and warrant the clinical development in the treatment of HNSCC.

WMJ-8-B, a novel hydroxamate derivative, induces MDA-MB-231 breast cancer cell death via the SHP-1-STAT3-survivin cascade

BACKGROUND AND PURPOSE

Histone deacetylase (HDAC) inhibitors have been demonstrate to have broad-spectrum anti-tumour properties and have attracted lots of attention in the field of drug discovery. However, the underlying anti-tumour mechanisms of HDAC inhibitors remain incompletely understood. In this study, we aimed to characterize the underlying mechanisms through which the novel hydroxamate-based HDAC inhibitor, WMJ-8-B, induces the death of MDA-MB-231 breast cancer cells.

EXPERIMENTAL APPROACH

Effects of WMJ-8-B on cell viability, cell cycle distribution, apoptosis and signalling molecules were analysed by the MTT assay, flowcytometric analysis, immunoblotting, reporter assay, chromatin immunoprecipitation analysis and use of siRNAs. A xenograft model was used to determine anti-tumour effects of WMJ-8-B in vivo.

KEY RESULTS

WMJ-8-B induced survivin reduction, G2/M cell cycle arrest and apoptosis in MDA-MB-231 cells. STAT3 phosphorylation, transactivity and its binding to the survivin promoter region were reduced in WMJ-8-B-treated cells. WMJ-8-B activated the protein phosphatase SHP-1 and when SHP-1 signalling was blocked, the effects of WMJ-8-B on STAT3 phosphorylation and survivin levels were abolished. However, WMJ-8-B increased the transcription factor Sp1 binding to the p21 promoter region and enhanced p21 levels. Moreover, WMJ-8-B induced α-tubulin acetylation and disrupted microtubule assembly. Inhibition of HDACs was shown to contribute to WMJ-8-B's actions. Furthermore, WMJ-8-B suppressed the growth of MDA-MB-231 xenografts in mammary fat pads in vivo.

CONCLUSIONS AND IMPLICATIONS

The SHP-1-STAT3-survivin and Sp1-p21 cascades are involved in WMJ-8-B-induced MDA-MB-231 breast cancer cell death. These results also indicate the potential of WMJ-8-B as a lead compound for treatment of breast cancer and warrant its clinical development.

Synthesis of Pyrrolo[1,2-a]pyrimidine Enantiomers via Domino Ring-Closure followed by Retro Diels-Alder Protocol

From 2-aminonorbornene hydroxamic acids, a simple and efficient method for the preparation of pyrrolo[1,2-a]pyrimidine enantiomers is reported. The synthesis is based on domino ring-closure followed by microwave-induced retro Diels-Alder (RDA) protocols, where the chirality of the desired products is transferred from norbornene derivatives. The stereochemistry of the synthesized compounds was proven by X-ray crystallography. The absolute configuration of the product is determined by the configuration of the starting amino hydroxamic acid.

Unprecedented Binding Mode of Hydroxamate-Based Inhibitors of Glutamate Carboxypeptidase II: Structural Characterization and Biological Activity

Inhibition of glutamate carboxypeptidase II (GCPII) is effective in preclinical models of neurological disorders associated with excessive activation of glutamatergic systems. Here we report synthesis, structural characterization, and biological activity of new hydroxamic acid-based inhibitors with nanomolar affinity for human GCPII. Crystal structures of GCPII/hydroxamate complexes revealed an unprecedented binding mode in which the putative P1' glutarate occupies the spacious entrance funnel rather than the conserved glutamate-binding S1' pocket. This unique binding mode provides a mechanistic explanation for the structure-activity relationship data, most notably the lack of enantiospecificity and the tolerance for bulky/hydrophobic functions as substituents of a canonical glutarate moiety. The in vivo pharmacokinetics profile of one of the inhibitors will be presented along with analgesic efficacy data from the rat chronic constrictive injury model of neuropathic pain.

Targeting cancer cells with oleanolic and ursolic acid derived hydroxamates

Oleanolic and ursolic acid derived hydroxamates were easily obtained from their parent compounds; they were screened for their cytotoxicity applying SRB assays employing several human tumor cell lines. Low EC50 values were determined for compounds in which the nitrogen as well as the oxygen in the hydroxamic acid part still holds acidic hydrogens. Thus, ursolic acid derived compounds having at least an OH and/or NH moiety in the hydroxamate part of the molecule showed good cytotoxicity but they are significantly less selective for the tumor cells than oleanolic acid derived compounds. Good results were determined for oleanolic acid derived 7 for tumor cell lines 518A2 (melanoma, EC50=3.3 μM), A2780 (ovarian carcinoma, EC50=3.4 μM) and HT29 (colon adenocarcinoma, EC50=5.6 μM) while being significantly less cytotoxic for fibroblasts (EC50=20.4 μM).

The effects of a novel aliphatic-chain hydroxamate derivative WMJ-S-001 in HCT116 colorectal cancer cell death

Hydroxamate derivatives have attracted considerable attention due to their broad pharmacological properties and have been extensively investigated. We recently demonstrated that WMJ-S-001, a novel aliphatic hydroxamate derivative, exhibits anti-inflammatory and anti-angiogenic activities. In this study, we explored the underlying mechanisms by which WMJ-S-001 induces HCT116 colorectal cancer cell death. WMJ-S-001 inhibited cell proliferation and induced cell apoptosis in HCT116 cells. These actions were associated with AMP-activated protein kinase (AMPK) and p38 mitogen-activated protein kinase (MAPK) activation, p53 phosphorylation and acetylation, as well as the modulation of p21(cip/Waf1), cyclin D1, survivin and Bax. AMPK-p38MAPK signaling blockade reduced WMJ-S-001-induced p53 phosphorylation. Transfection with AMPK dominant negative mutant (DN) reduced WMJ-S-001's effects on p53 and Sp1 binding to the survivn promoter region. Transfection with HDAC3-Flag or HDAC4-Flag also abrogated WMJ-S-001's enhancing effect on p53 acetylation. WMJ-S-001's actions on p21(cip/Waf1), cyclin D1, survivin, Bax were reduced in p53-null HCT116 cells. Furthermore, WMJ-S-001 was shown to suppress the growth of subcutaneous xenografts of HCT116 cells in vivo. In summary, the death of HCT116 colorectal cancer cells exposed to WMJ-S-001 may involve AMPK-p38MAPK-p53-survivin cascade. These results support the role of WMJ-S-001 as a potential drug candidate and warrant the clinical development in the treatment of cancer.

WMJ-S-001, a novel aliphatic hydroxamate derivative, exhibits anti-angiogenic activities via Src-homology-2-domain-containing protein tyrosine phosphatase 1

Angiogenesis, one of the major routes for tumor invasion and metastasis represents a rational target for therapeutic intervention. Recent development in drug discovery has highlighted the diverse biological and pharmacological properties of hydroxamate derivatives. In this study, we characterized the anti-angiogenic activities of a novel aliphatic hydroxamate, WMJ-S-001, in an effort to develop novel angiogenesis inhibitors. WMJ-S-001 inhibited vascular endothelial growth factor (VEGF)-A-induced proliferation, invasion and endothelial tube formation of human umbilical endothelial cells (HUVECs). WMJ-S-001 suppressed VEGF-A-induced microvessel sprouting from aortic rings, and attenuated angiogenesis in in vivo mouse xenograft models. In addition, WMJ-S-001 inhibited the phosphorylations of VEGFR2, Src, FAK, Akt and ERK in VEGF-A-stimulated HUVECs. WMJ-S-001 caused an increase in SHP-1 phosphatase activity, whereas NSC-87877, a SHP-1 inhibitor, restored WMJ-S-001 suppression of VEGFR2 phosphorylation and cell proliferation. Furthermore, WMJ-S-001 inhibited cell cycle progression and induced cell apoptosis in HUVECs. These results are associated with p53 phosphorylation and acetylation and the modulation of p21 and survivin. Taken together, WMJ-S-001 was shown to modulate vascular endothelial cell remodeling through inhibiting VEGFR2 signaling and induction of apoptosis. These results also support the role of WMJ-S-001 as a potential drug candidate and warrant the clinical development in the treatment of cancer.

Synthesis and antimalarial evaluation of prodrugs of novel fosmidomycin analogues

The continuous development of drug resistance by Plasmodium falciparum, the agent responsible for the most severe forms of malaria, creates the need for the development of novel drugs to fight this disease. Fosmidomycin is an effective antimalarial and potent antibiotic, known to act by inhibiting the enzyme 1-deoxy-d-xylulose-5-phosphate reductoisomerase (DXR), essential for the synthesis of isoprenoids in eubacteria and plasmodia, but not in humans. In this study, novel constrained cyclic prodrug analogues of fosmidomycin were synthesized. One, in which the hydroxamate function is incorporated into a six-membered ring, was found have higher antimalarial activity than fosmidomycin against the chloroquine and mefloquine resistant P. falciparum Dd2 strain. In addition, it showed very low cytotoxicity against cultured human cells.

WMJ-S-001, a novel aliphatic hydroxamate derivative, exhibits anti-inflammatory properties via MKP-1 in LPS-stimulated RAW264.7 macrophages

BACKGROUND AND PURPOSE

Hydroxamate derivatives have attracted considerable attention because of their broad pharmacological properties. Recent studies reported their potential use in the treatment of cardiovascular diseases, arthritis and infectious diseases. However, the mechanisms of the anti-inflammatory effects of hydroxamate derivatives remain to be elucidated. In an effort to develop a novel pharmacological agent that could suppress abnormally activated macrophages, we investigated a novel aliphatic hydroxamate derivative, WMJ-S-001, and explored its anti-inflammatory mechanisms.

EXPERIMENTAL APPROACH

RAW264.7 macrophages were exposed to LPS in the absence or presence of WMJ-S-001. COX-2 expression and signalling molecules activated by LPS were assessed.

KEY RESULTS

LPS-induced COX-2 expression was suppressed by WMJ-S-001. WMJ-S-001 inhibited p38MAPK, NF-κB subunit p65 and CCAAT/enhancer-binding protein (C/EBP)β phosphorylation in cells exposed to LPS. Treatment of cells with a p38MAPK inhibitor (p38MAPK inhibitor III) markedly inhibited LPS-induced p65 and C/EBPβ phosphorylation and COX-2 expression. LPS-increased p65 and C/EBPβ binding to the COX-2 promoter region was suppressed in the presence of WMJ-S-001. In addition, WMJ-S-001 suppression of p38MAPK, p65 and C/EBPβ phosphorylation, and subsequent COX-2 expression were restored in cells transfected with a dominant-negative (DN) mutant of MAPK phosphatase-1 (MKP-1). WMJ-S-001 also caused an increase in MKP-1 activity in RAW264.7 macrophages.

CONCLUSIONS AND IMPLICATIONS

WMJ-S-001 may activate MKP-1, which then dephosphorylates p38MAPK, resulting in a decrease in p65 and C/EBPβ binding to the COX-2 promoter region and COX-2 down-regulation in LPS-stimulated RAW264.7 macrophages. The present study suggests that WMJ-S-001 may be a potential drug candidate for alleviating LPS-associated inflammatory diseases.

Biological activities of novel pyrazolyl hydroxamic acid derivatives against human lung cancer cell line A549

We synthesized a series of novel pyrazolyl hydroxamic acid derivatives (4a-4l) and investigated their biological activities against human lung cancer cell line A549 in vitro to determine their mechanism of action. The results showed that the majority of derivatives had inhibitory effects on the growth of A549 cancer cells in dose and time-dependent manners, in which the compounds 4b, 4f, 4h and 4j (10 μM) exerted more effective anti-proliferation activity. However, it should be noted that 4j may result in necrosis at 10 μM. Furthermore, the three compounds 4b, 4f and 4h induced cell cycle arrest at G1 phase and triggered autophagy, but could not obviously induce apoptosis and necrosis under the stimulatory condition. Therefore, the pyrazolyl hydroxamic acid derivatives 4b, 4f and 4h can be used to investigate the regulatory mechanism of autophagy and offer new approaches to the prevention of lung cancer.

Metabolite induction via microorganism co-culture: a potential way to enhance chemical diversity for drug discovery

Microorganisms have a long track record as important sources of novel bioactive natural products, particularly in the field of drug discovery. While microbes have been shown to biosynthesize a wide array of molecules, recent advances in genome sequencing have revealed that such organisms have the potential to yield even more structurally diverse secondary metabolites. Thus, many microbial gene clusters may be silent under standard laboratory growth conditions. In the last ten years, several methods have been developed to aid in the activation of these cryptic biosynthetic pathways. In addition to the techniques that demand prior knowledge of the genome sequences of the studied microorganisms, several genome sequence-independent tools have been developed. One of these approaches is microorganism co-culture, involving the cultivation of two or more microorganisms in the same confined environment. Microorganism co-culture is inspired by the natural microbe communities that are omnipresent in nature. Within these communities, microbes interact through signaling or defense molecules. Such compounds, produced dynamically, are of potential interest as new leads for drug discovery. Microorganism co-culture can be achieved in either solid or liquid media and has recently been used increasingly extensively to study natural interactions and discover new bioactive metabolites. Because of the complexity of microbial extracts, advanced analytical methods (e.g., mass spectrometry methods and metabolomics) are key for the successful detection and identification of co-culture-induced metabolites. This review focuses on co-culture studies that aim to increase the diversity of metabolites obtained from microbes. The various strategies are summarized with a special emphasis on the multiple methods of performing co-culture experiments. The analytical approaches for studying these interaction phenomena are discussed, and the chemical diversity and biological activity observed among the induced metabolites are described.