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PubMed1984

Specific inhibition of human leukocyte elastase by substituted alpha-pyrones.

Several a-pyrones have been synthesized and investigated for their in vitro inhibitory activity using a-chymotrypsin (a-CT), porcine pancreatic elastase (PPE) and human leukocyte elastase (HLE). 4-Hydroxy-6-undecyl-2H-pyran-2-one 4, 4-Hydroxy-6-[(1-butyl)heptyl]-2H-pyran-2-one 5 and 4-Methoxy-6-[(1-butyl) heptyl]-2H-pyran-2-one 6 were found to be specific inhibitors of HLE. These compounds constitute a promising new class of HLE inhibitors.

Chemical Phenomena↗
PubMed2002

Production and biotransformation of 6-pentyl-alpha-pyrone by Trichoderma harzianum in two-phase culture systems.

The final concentration of 6-pentyl-a-pyrone (6PP) produced in cultures of Trichoderma spp. is limited by the fact that inhibition of biomass growth occurs at 6PP concentrations as low as 100 mg/l. The aim of this work was to evaluate liquid-liquid extractive fermentation systems as an alternative to overcome the toxicity problems and to increase the production of 6PP by this fungus. Two alkanes (n-decane and n-hexadecane) and two dicarboxylic esters (dibutyl phthalate and dioctyl phthalate) were evaluated in shake flask cultures. The highest 6PP production (173 ppm) was achieved when n-hexadecane was used, being 3.5-fold the maximum 6PP concentration of a culture without the solvent. Cultivation of Trichoderma harzianum in a 10-1 bioreactor with n-hexadecane yielded 6PP production ninefold higher than that from control cultures. However, 6PP production in the bioreactor (83 ppm) was lower than in shake flasks. Differences in the power drawn to the fluid at each scale could account for such behavior. Even in the presence of the solvent, 6PP content decreased after reaching its maximal concentration.

Bioreactors↗
PubMed2005

Efficient production of 2-pyrone 4,6-dicarboxylic acid as a novel polymer-based material from protocatechuate by microbial function.

Sphingomonas paucimobilis SYK-6, which can degrade various low molecular weight compounds derived from plant polyphenols such as lignin, lignan, and tannin, metabolizes these substances via 2-pyrone-4,6-dicarboxylic acid (PDC). We focused on this metabolic intermediate as a potential raw material for novel, bio-based polymers. We cloned the ligAB and ligC genes of SYK-6, which respectively encode protocatechuate 4,5-dioxygenase and 4-carboxy-2-hydroxymuconate-6-semialdehyde dehydrogenase, into a broad host range plasmid vector, pKT230MC. The resulting plasmid, pDVABC, was introduced into the PpY1100 strain of Pseudomonas putida, and we found that PDC could be stably produced from protocatechuate and accumulated. In addition, we examined the efficiency of production of PDC from protocatechuate on a 5-L scale in a Luria-Bertani medium containing 100 mM glucose and determined that PDC was stably produced from protocatechuate to yield 10 g/L or more.

Bacterial Proteins↗
PubMed2001

In vitro study of the insulin-like action of vanadyl-pyrone and -pyridinone complexes with a VO(O4) coordination mode.

The insulin-like action of a novel class of potential insulin-mimetic complexes was investigated in terms of free fatty acid (FFA) release from isolated rat adipocytes. Vanadyl complexes such as VO(ema)2 [(bis(2-ethyl-3-hydroxy-4-pyrone)VO], VO(mpp)2 [bis (3-hydroxy-2-methyl-4(1H)-pyridinone)VO], VO(dmpp)2 [bis(1,2-dimethyl-3-hydroxy-4(1H)-pyridinone)VO] and VO(empp)2 [bis(2-ethyl-3-hydroxy-1-methyl-4(1H)-pyridinone)VO] were tested together with vanadyl sulfate for comparison. The inhibitory effect of the vanadium complexes on FFA release, from rat adipocytes treated with epinephrine, is dependent on concentration and for that reason the results are reported in terms of the IC50 value, the 50% inhibition concentration. The results show that all the complexes have an inhibitory effect on FFA release and that two pyridinone complexes, VO(mpp)2 and VO(empp)2, have a significantly better insulin-mimetic activity than that of vanadyl sulfate.

Adipocytes↗
PubMedDate not supplied

Novel tricyclic pyrone compounds prevent intracellular APP C99-induced cell death.

Alzheimer's disease (AD) is an age-related neurodegenerative disorder characterized by the progressive and global loss of cognitive functions. Pathological features include a loss of neurons in vulnerable brain regions and the extracellular deposition of abnormal protein aggregates known as amyloid plaques. Amyloid-beta protein (A beta is the major component of amyloid plaques and is derived from a larger transmembrane glycoprotein, termed amyloid beta protein precursor (APP), by proteolysis. The AD research has focused on A beta production and metabolism, its extracellular deposition, and its cellular toxicity. Recent evidence, however, suggests that A beta as well as the C-terminal fragments (CTF) of APP can accumulate intraneuronally. The neuronal loss and synaptic transmission deficit in AD may therefore depend on intraneuronal accumulation of A beta/CTF rather than on extracellular plaque formation. Accordingly, we propose that one of the primary targets of therapeutic intervention should be intracellular A beta/CTF and its toxic cellular effect. We have established a cell-culture model in which the neurons degenerate on induction of endogenous expression of A beta/CTF of APP. These cultures have been used to test whether tricyclic pyrone (TP) compounds may prevent A beta/CTF-mediated neuronal death. The results to date have been encouraging. Lead compounds will now be selected for their abilities to ameliorate A beta/CTF-mediated pathology in transgenic mice. Our hope is that these compounds may eventually prove beneficial for the prevention and treatment of AD.

Alzheimer Disease↗
PubMed1995

Pyrone hydroperoxide formation during the Maillard reaction and its implication in biological systems.

Hydroperoxide formation during Maillard reaction (amino-carbonyl reaction) was investigated using luminol-chemiluminescence-high performance liquid chromatography (CL-HPLC). From the equimolar reaction mixture of 1 M beta-alanine/D-glucose in phosphate buffer (pH 8.0) at 95 degrees C, two hydroperoxides and H2O2 were detected as chemiluminescent products in CL-HPLC, and the yields were proportional to the browning development. One of these hydroperoxides was isolated and identified as 3-hydroxy-5-hydroperoxy-2-methyl-5,6-dihydropyran-4-one (HMDP, pyrone hydroperoxide) by fast atom bombardment mass spectrometry. The HMDP formation was also confirmed in L-lysine/D-glucose and in bovine serum albumin/D-glucose with the physiological incubation at 37 degrees C for 4 days and 3 wk, respectively. Incubation at 37 degrees C of human plasma containing 5.5-25.0 mM of D-glucose for 60 h showed the glucose concentration-dependent formation of HMDP (10-35 microM of H2O2 equivalence). The HMDP was negative to thiobarbituric acid reaction and was degraded by peroxidases such as horseradish peroxidase, Athromyces ramosus peroxidase, heated cytochrome c, and microperoxidase. The results strongly suggested the formation of such hydroperoxide even in biological Maillard reaction termed as glycation, and implied its contribution in pathogenesis and oxidative lesions associated with hyperglycemia.

Animals↗
PubMed2004

Enzymatic formation of long-chain polyketide pyrones by plant type III polyketide synthases.

Recombinant chalcone synthase (CHS) from Scutellaria baicalensis and stilbene synthase (STS) from Arachis hypogaea accepted CoA esters of long-chain fatty acid (CHS up to the C12 ester, while STS up to the C14 ester) as a starter substrate, and carried out sequential condensations with malonyl-CoA, leading to formation of triketide and tetraketide alpha-pyrones. Interestingly, the C6, C8, and C10 esters were kinetically favored by the enzymes over the physiological starter substrate; the kcat/KM values were 1.2- to 1.9-fold higher than that of p-coumaroyl-CoA. The catalytic diversities of the enzymes provided further mechanistic insights into the type III PKS reactions, and suggested involvement of the CHS-superfamily enzymes in the biosynthesis of long-chain alkyl polyphenols such as urushiol and ginkgolic acid in plants.

Acyl Coenzyme A↗
PubMed2001

Passifloricins, polyketides alpha-pyrones from Passiflora foetida resin.

Three polyketides alpha-pyrones, named passifloricins, were isolated from Passiflora foetida resin; their structures and relative configurations were assigned through 2D NMR spectroscopic analyses. These types of compounds were not detected in other passion flowers.

Magnetic Resonance Spectroscopy↗
PubMed1998

Styryl-pyrones from Goniothalamus arvensis.

Two novel styrl-pyrones, (+)-garvensintriol and (+)-etharvendiol, together with a known cytotoxic furano-furone, (+)-goniofufurone, have been isolated from the stem bark of Goniothalamus arvensis. A different relative configuration, cis-erythro-erythro for garvensintriol and cis-threo-erythro for etharvendiol, is established, and their absolute stereochemistry is discussed.

Magnetic Resonance Spectroscopy↗
PubMed1999

Two 6-substituted 5,6-dihydro-alpha-pyrones from Ravensara anisata.

The leaves and bark dichloromethane extracts of Ravensara anisata showed antifungal activity against the yeast Candida albicans and the phytopathogenic fungus Cladosporium cucumerinum in bioautographic TLC assays. Activity-guided fractionation afforded two new alpha-pyrones: 6R*-(4R*-acetoxy-2S*-hydroxy- 8-phenyloctyl)-5,6-dihydro-2-H-pyran-2-one and 6R*-(2S*-acetoxy-4R*- hydroxy-8-phenyloctyl)-5,6-dihydro-2-H-pyran-2-one. Their structures have been established by NMR spectroscopy, chemical methods and X-ray crystallographic analysis. The antifungal activity against C. albicans and C. cucumerinum was determined for both compounds.

Candida albicans↗
PubMed2003

Four novel bis-(naphtho-gamma-pyrones) isolated from Fusarium species as inhibitors of HIV-1 integrase.

Integration of viral DNA into host cell DNA is an essential step in retroviral (HIV-1) replication and is catalyzed by HIV-1 integrase. HIV-1 integrase is a novel therapeutic target and is the focus of efforts to identify effective inhibitors that will prevent/or cure HIV infections. Four novel naphtho-gamma-pyrones, belonging to the chaetochromin and ustilaginoidin family, were discovered as inhibitors of HIV-1 integrase from the screening of fungal extracts using a recombinant in vitro assay. These compounds inhibit both the coupled and strand transfer activity of HIV-1 integrase with IC(50) values of 1-3 and 4-12 microM, respectively. The discovery, structure elucidation, chemical modification and the structure-activity relationship of these compounds are described.

Anti-HIV Agents↗
PubMed2026

Systematic Genome Mining of Peptide Metallophore Pathways Uncovers Novel Dibenzo-α-Pyrone Siderophores in Streptomyces sp. HB-R818.

Metallophores are metal-chelating natural products that enable microorganisms to acquire essential metal ions and mediate processes such as iron uptake, quorum sensing, and interspecies competition. Metallophores also display potent antimicrobial and anticancer activities, highlighting their biomedical and biotechnological potential. Despite Streptomyces being prolific producers of bioactive metabolites, their metallophore pathways remain largely unexplored. Here, we systematically mined 519 reference Streptomyces genomes to elucidate the distribution, diversity, and structural features of metallophores and identified a new metallophore biosynthetic gene cluster (BGC) (ser) from sponge-derived Streptomyces sp. HB-R818. Using a metabologenomics-based strategy, five new siderophore analogs serobactins A-E (1-5) and known enterobactin (6) were isolated. These compounds show potential to inhibit tumor invasion and feature a unique dibenzo-α-pyrone scaffold in structure, formed through the cyclization of an extra 2,3-dihydroxybenzoic acid with 2,3-dihydroxybenzoyl serine. The BGC (ser) was validated by the nonribosomal peptide synthetase gene knockout; the biosynthesis of 1-6 was proposed.

Siderophores↗
PubMed1986

X-ray diffraction analysis of the inactivation of chymotrypsin by 3-benzyl-6-chloro-2-pyrone.

The inactivation of chymotrypsin by 3-benzyl-6-chloro-2-pyrone has been studied. A covalent adduct is formed that deacylates slowly with a half-life of 23 h. X-ray diffraction analysis at 1.9-A resolution of the inactivator-enzyme complex shows that the gamma-oxygen of the active-site serine (serine-195) is covalently attached to C-1 of (Z)-2-benzylpentenedioic acid, the benzyl group of the inactivator is held in the hydrophobic specificity pocket of the enzyme, and the free carboxylate forms a salt bridge with the active-site histidine (histidine-57). The conformational changes that occur in the protein as a result of complexation are described. It is proposed that formation of the salt bridge prevents access of water and, therefore, hydrolysis of the acyl-enzyme.

Binding Sites↗
PubMed2006

Tris(pyrone) chelates of Gd(III) as high solubility MRI-CA.

Two tripodal, hexadentate pyrone-based chelators have been prepared. These ligands form stable, soluble complexes with gadolinium(III). The complexes show aqueous stability comparable to that of [Gd(DTPA)]2- at pH 7.4. Evaluation by relaxometry shows that these complexes have two inner-sphere water molecules and a very fast water exchange rate. The solution behavior of these complexes suggests that they may be attractive as high relaxivity, next-generation magnetic resonance imaging contrast agents.

Chelating Agents↗