Search results for "Lactones"

Oxidative DNA damage and disturbance of antioxidant capacity by alternariol in Caco-2 cells

2015

Oxidative stress occurs as a consequence of an imbalance between the prooxidant/antioxidant systems, causing an increase of intracellular generation of reactive oxygen species. Alternariol (AOH), a mycotoxin produced by Alternaria sp. can alter the action of glutathione (GSH) and the enzymes involved in the redox system, causing damage to cellular macromolecules such as DNA. The aims of this work were to determine the induction of oxidative stress by the antioxidant defenses imbalance in relation to glutathione (GSH), glutathione reductase (GR), glutathione transferase (GST), glutathione peroxidase (GPx) levels and DNA damage in Caco-2 cells derived from adenocarcinoma human colon. Oxidativ…

Interaction of an odorant lactone with model phospholipid bilayers and its strong fluidizing action in yeast membrane

2003

International audience; Some odorant lactones are naturally present in fruits or in fermented products; they can also be used as food additives and can be produced by microorganisms at the industrial scale by biotechnological processes. Gamma-decalactone was previously shown to have antimicrobial properties. We determined by infrared spectroscopy measurements that this compound rapidly diffused into model phospholipid bilayers (within 2 min), modifying the general physical state of a dimyristoyl-L-alpha-phosphatidylcholine (DMPC) film. In vivo, the lactone strongly increased membrane fluidity in the model yeast Yarrowia lipolytica, as evaluated by fluorescence anisotropy measurements. This …

Antiproliferative activity against leukemia cells of sesquiterpene lactones from the Turkish endemic plant Centaurea drabifolia subsp. detonsa

2017

The apolar organic extract obtained from aerial parts of Centaurea drabifolia Sibth. & Sm. subsp. detonsa (Bornm.) Wagenitz, growing wild in Turkey, was investigated for the first time for its secondary metabolite composition. Seven sesquiterpene lactones belonging to the guaiane class (1-7), including the new compound 4, along with a fatty acid lactone derivative (8), were isolated. The structures of these compounds were established by spectroscopic analysis, including 2D NMR spectroscopic techniques, with the stereostructure of the new guaiane 4 determined with the help of MTPA derivatization. Cytotoxic activities of compounds 1-7 were evaluated against two cancer cell lines, namely acute…

Kinetic characterization of mitochondrial complex I inhibitors using annonaceous acetogenins

1999

The NADH:ubiquinone oxidoreductase (complex I) of the mitochondrial respiratory chain is by far the largest and most complicated of the proton-translocating enzymes involved in the oxidative phosphorylation. Many clues regarding the electron pathways from matrix NADH to membrane ubiquinone and the links of this process with the translocation of protons are highly controversial. Different types of inhibitors become valuable tools to dissect the electron and proton pathways of this complex enzyme. Therefore, further knowledge of the mode of action of complex I inhibitors is needed to understand the underlying mechanism of energy conservation. This study presents for the first time a detailed …

Aroma production by solid state fermentation

2018

The adaptation of the production of γ-decalactones from submerged fermentation (SmF) to solid state fermentation (SSF) by Yarrowia lipolytica was investigated in this work. First of all, different solid matrices (corncob, cellulose sponge, luffa sponge, and castor seeds) were used for the first adaptation of the production of γ-décalactones. Luffa sponge appeared to be the most interesting solid support on which lactones were produced in higher concentrations than in the other solid matrices used. Then, the production of lactones using luffa sponge as the solid support was carried out in three types of SSF reactors to monitor different aeration conditions (without aeration, with a static ae…

Stereoselective Synthesis and Structural Correction of the Naturally Occurring Lactone Stagonolide G

2010

A convergent synthesis of the structure proposed for the naturally occurring lactone stagonolide G is described. All three stereocenters were created with the aid of asymmetric Brown allylations. The lactone ring was built by means of a ring-closing metathesis (RCM). The synthetic and the natural compound differed in their spectral properties. A new structure is now proposed for stagonolide G and demonstrated by means of a chemical transformation.

New reagent for the detection of sesquiterpene lactones by thin-layer chromatography.

1984

Straightforward Stereoselective Access to Cyclic Peptidomimetics

2009

The preparation of cyclic dipeptide mimetics from chiral imino lactones derived from (R)-phenylglycinol is described. Key steps of the synthetic route included the fully stereoselective construction of a quaternary center, the formation of six-, seven-, or eight-membered lactams by means of an RCM cyclization, and the introduction of a new amino group within the lactam ring. The synthesis of a tripeptide mimetic is also reported.

Stereoselective Synthesis of (+)-Boronolide

2002

The delta-lactone boronolide (+)-1, a pharmacologically active, naturally occurring product, has been synthesized in enantiopure form with L-erythrulose as the chiral starting material. The key steps of the synthesis were a highly stereoselective aldol-reduction one-pot sequence, an indium-mediated diastereoselective aldehyde allylation, and a ring-closing metathesis.

Stereoselective synthesis of the cytotoxic 14-membered macrolide aspergillide A.

2010

A stereoselective synthesis of the cytotoxic 14-membered macrolide aspergillide A has been performed. The preparation of a cis-2,6-disubstituted tetrahydropyran ring via stereoselective reduction of an intermediate cyclic hemiacetal was one key feature of the synthesis. The macrocyclic lactone ring was created by means of a ring-closing metathesis (RCM), whereby the new C=C bond displayed exclusively the undesired Z configuration. Conversion to the required E configuration was achieved via photochemical isomerization.