Jesús Ángel de la Fuente

Aldose reductase inhibitors from natural sources

This review covers aldose reductase inhibitors (ARIs) isolated from natural sources. Compounds in the review are grouped according to the source from which they have been isolated: terrestrial, marine, or microorganism and the in vitro inhibitory activity of the compounds is also showed. The literature, both journals and patents, up to June 2002 is reviewed and 86 references are cited.

Identification of a Series of Tricyclic Natural Products as Potent Broad-Spectrum Inhibitors of Metallo-β-Lactamases

ABSTRACT This work describes the discovery and characterization of a novel series of tricyclic natural product-derived metallo-β-lactamase inhibitors. Natural product screening of the Bacillus cereus II enzyme identified an extract from a strain of Chaetomium funicola with inhibitory activity against metallo-β-lactamases. SB236050, SB238569, and SB236049 were successfully extracted and purified from this extract. The most active of these compounds was SB238569, which possessed Ki values of 79, 17, and 3.4 μM for the Bacillus cereus II, Pseudomonas aeruginosa IMP-1, and Bacteroides fragilis CfiA metallo-β-lactamases, respectively, yet none of the compounds exhibited any inhibitory activity against the Stenotrophomonas maltophilia L-1 metallo-β-lactamase (50% inhibitory concentration > 1,000 μM). The lack of activity against angiotensin-converting enzyme and serine β-lactamases demonstrated the selective nature of these compounds. The crystal structure of SB236050 complexed in the active site of CfiA has been obtained to a resolution of 2.5 Å. SB236050 exhibits key polar interactions with Lys184, Asn193, and His162 and a stacking interaction with the indole ring of Trp49 in the flap, which is in the closed conformation over the active site groove. SB236050 and SB238569 also demonstrate good antibacterial synergy with meropenem. Eight micrograms of SB236050 per ml gave rise to an eightfold drop in the MIC of meropenem for two clinical isolates of B. fragilis producing CfiA, making these strains sensitive to meropenem (MIC ≤ 4 μg/ml). Consequently, this series of metallo-β-lactamase inhibitors exhibit the most promising antibacterial synergy activity so far observed against organisms producing metallo-β-lactamases.

HPMA Copolymer-1,5-Diazaanthraquinone Conjugates as Novel Anticancer Therapeutics

1,5-Diazaanthraquinones (DAQs) are promising anticancer drugs, however, their clinical potential is limited due to poor solubility. Conjugation of anticancer agents to hydrophilic water-soluble polymers can overcome this problem and has already been used to generate conjugates with demonstrated clinical benefit. Here a library of N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer conjugates containing a novel amino-functionalised 1,5-diazaanthraquinone derivative (amino-DAQ) have been synthesised. The conjugates were fully characterised by UV, HPLC, SEC, FT-Raman and NMR spectroscopy. Conjugation to HPMA copolymers improved amino-DAQ aqueous solubility (>7-fold). The HPMA copolymer-amino-DAQ conjugates were slightly less haemolytic than the parent compound (2% Hb released in 1 h for conjugate HPMA copolymer-GFLG (5 mol%)-amino-DAQ conjugate compared to 13% obtained with amino-DAQ). When conjugates were incubated with isolated rat liver lysosomal enzymes (Tritosomes) the rate of amino-DAQ release was influenced by both drug loading and the composition of the peptidyl side chain used to link the drug to the carrier. The higher the drug loading the lower the rate of drug release. Whereas the GG linker did not release amino-DAQ, up to 26% of the amino-DAQ was released from a GFLG linker over 24 h. The in vitro cytotoxicity of these conjugates was evaluated against two different cell lines, B16F10 murine melanoma and MCF-7 human breast cancer cells. HPMA copolymer-amino-DAQ conjugates, which are internalised by cells by the endocytic pathway, showed much lower in vitro cytotoxicity (IC50 for HPMA copolymer-GFLG (5 mol%)-amino-DAQ conjugate > 397 μM drug-equiv.) than the free drug (the IC50 for amino-DAQ was 12.6 and 2.8 μM against the B16F10 murine melanoma and the MCF-7 breast cancer cell line, respectively). Nonetheless, the observed lysosomal activation of the HPMA copolymer-GFLG-amino-DAQ conjugates, suggests that evaluation of the antitumour potential in vivo is warranted.

Agrochelin, a new cytotoxic alkaloid from the marine bacteria Agrobacterium sp.

Agrochelin (1), a new cytotoxic thiazole alkaloid, has been isolated from the fermentation broth of a marine unicellular bacterium belonging to genus Agrobacterium. Its structure was determined from spectral data and chemical transformations. Agrochelin showed chelating properties to the Zn2+ ion.

A C-ring regioisomer of the marine alkaloid meridine exhibits selective in vitro cytotoxicity for solid tumours.

9-Hydroxybenzo[b]pyrido[4,3,2-de](1,10)-phenantrolin-8-one (1), a regioisomer of the marine alkaloid meridine, was synthesized from 5,8-dimethoxy-6-nitro-4(1H)-quinolinone in eight steps and 23% overall yield. A shorter route was also investigated, based on the hetero Diels-Alder reaction between o-nitrocinnamaldehyde dimethylhydrazone and 4-halogen-6-bromo-5,8-quinolinequinones followed by reductive cyclization onto the C-5 carbonyl of the quinone. Compound 1 showed a remarkable in vitro cytotoxicity, with a pattern of selectivity towards solid tumours that is not found in the reference alkaloid, the activity against the human lung carcinoma (A-549) being particularly noteworthy. The activities of meridine and compound 1 as inhibitors of topoisomerase II were also significantly different.

The identification of structurally novel, selective, orally bioavailable positive modulators of mGluR2

The optimisation of an HTS hit series (1) leading to the identification of structurally novel, selective, orally bioavailable mGluR2 positive modulators GSK1331258 and GSK1331268 is described. Structure-activity relationships, attenuation of dopaminergic activity, and potentiation of mGluR2 responses in rat hippocampal MPP-DG synapses are also reported.

SYNTHESIS OF 1,2,3,4-TETRAHYDROASCIDIDEMIN

Abstract 1,2,3,4-Tetrahydroascididemin was synthesized in six steps from 2-nitro-3,6-dimethoxy-acetophenone. The core linear tetracyclic pyrido[2,3- b ]acridine system ( 6 ) was prepared through combination of a Friedlander reaction and an hetero Diels-Alder cycloaddition as the key steps, and the fifth ring was created using a tandem Mannich reaction-intramolecular imine formation. 1,2,3,4-Tetrahydroascididemin showed excellent in vitro antitumour activity, which was particularly selective for the human non-small cell lung cancer cell line (A-549).

A NOVEL NON NUCLEOSIDE COMPOUND WITH HIGH IN VITRO ANTI-HIV-1 ACTIVITY. ABSOLUTE STEREOCHEMISTRY DETERMINATION

Abstract Here we report a novel non-nucleoside compound, PM-92131(+), with in vitro anti-HIV-1 activity. This product was synthesized as a pure enantiomer via diastereomeric ester formation and selective crystallisation and its absolute stereochemistry was determined by X-ray diffraction analysis. Results from the activity assays suggest PM-92131(+) could be a promising new compound for further assessment as a potential anti-HIV-1 agent.

Structural Determinants of the Selectivity of 3-Benzyluracil-1-acetic Acids toward Human Enzymes Aldose Reductase and AKR1B10.

The human enzymes aldose reductase (AR) and AKR1B10 have been thoroughly explored in terms of their roles in diabetes, inflammatory disorders, and cancer. In this study we identified two new lead compounds, 2‐(3‐(4‐chloro‐3‐nitrobenzyl)‐2,4‐dioxo‐3,4‐dihydropyrimidin‐1(2H)‐yl)acetic acid (JF0048, 3) and 2‐(2,4‐dioxo‐3‐(2,3,4,5‐tetrabromo‐6‐methoxybenzyl)‐3,4‐dihydropyrimidin‐1(2H)‐yl)acetic acid (JF0049, 4), which selectively target these enzymes. Although 3 and 4 share the 3‐benzyluracil‐1‐acetic acid scaffold, they have different substituents in their aryl moieties. Inhibition studies along with thermodynamic and structural characterizations of both enzymes revealed that the chloronitrobenzyl moiety of compound 3 can open the AR specificity pocket but not that of the AKR1B10 cognate. In contrast, the larger atoms at the ortho and/or meta positions of compound 4 prevent the AR specificity pocket from opening due to steric hindrance and provide a tighter fit to the AKR1B10 inhibitor binding pocket, probably enhanced by the displacement of a disordered water molecule trapped in a hydrophobic subpocket, creating an enthalpic signature. Furthermore, this selectivity also occurs in the cell, which enables the development of a more efficient drug design strategy: compound 3 prevents sorbitol accumulation in human retinal ARPE‐19 cells, whereas 4 stops proliferation in human lung cancer NCI‐H460 cells.

Functional screening of selective mitochondrial inhibitors of Plasmodium

Phenotypic screening has produced most of the new chemical entities currently in clinical development for malaria, plus many lead compounds active against Plasmodium falciparum asexual stages. However, lack of knowledge about the mode of action of these compounds delays and may even hamper their future development. Identifying the mode of action of the inhibitors greatly helps to prioritise compounds for further development as novel antimalarials. Here we describe a whole-cell method to detect inhibitors of the mitochondrial electron transport chain, using oxygen consumption as high throughput readout in 384-well plate format. The usefulness of the method has been confirmed with the Tres Cantos Antimalarial Compound Set (TCAMS). The assay identified 124 respiratory inhibitors in TCAMS, seven of which were novel anti-plasmodial chemical structures never before described as mitochondrial inhibitors.