Biomimetic chemistry on the protection of cis phospholipid from the thiyl radical isomerization by common antioxidants

Lykakis, Ioannis N.; Ferreri, Carla; Chatgilialoglu, Chryssostomos

doi:10.3998/ark.5550190.p008.984

Cited by 7 publications

(1 citation statement)

References 41 publications

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“…Conjugated groups are strong inhibitors of double-bond isomerization. , However, upon its build-in, the conjugated lipid dimer ( L –H ) 2 ( 3 ) will undergo addition of S • radicals to form allylic adducts, S • + ( L –H ) 2 → S –( L –H ) 2 • + S H → S – L′ H– L . At higher thiol concentrations, these may contribute to the yield of cross-termination product 4 ( L S L′ H).…”

Section: Resultsmentioning

confidence: 99%

The Reaction of Thiyl Radical with Methyl Linoleate: Completing the Picture

et al. 2017

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Cis lipids can be converted by thiols and free radicals into trans lipids, which are therefore a valuable tell-tale for free radical activity in the cell's lipidome. Our previous studies have shown that polyunsaturated lipids are isomerized by alkanethiyl radicals (S) in a cycle propagated by reversible double-bond addition and terminated by radical H-abstraction from the lipid. A critical flaw in this picture has long been that the reported lipid abstraction rate from radiolysis studies is faster than addition-isomerization, implying that the "cycle" must be terminating faster than it is propagating! Herein, we resolved this longstanding puzzle by combining a detailed product analysis, with reinvestigation of the time-resolved kinetics, DFT calculations of the indicated pathways, and reformulation of the radical-stasis equations. We have determined thiol-coupled products in dilute solutions arise mainly from addition to the inside position of the bisallylic group, followed by rapid intramolecular H transfer, yielding allylic radicals (L + S ⇄ SL → SL') that are slowly reduced by thiol (SL' + SH → SL'H + S). The first-order grow-in rate of the L signal (k) may therefore be dominated by the addition-H-translocation rather than slower direct H-abstraction. Steady-state kinetic analysis of the new mechanism is consistent with products and the rates and trends for polyunsaturated fatty acids (PUFAs), monounsaturated fatty acids (MUFAs), and mixtures, with and without physiological [O]. Implications of this new paradigm for the thiol-ene reactivity fall in an interdisciplinary research area spanning from synthetic applications to metabolomics.

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Section: Resultsmentioning

confidence: 99%

The Reaction of Thiyl Radical with Methyl Linoleate: Completing the Picture

et al. 2017

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Titania‐Supported Gold Nanoparticles Catalyze the Selective Oxidation of Amines into Nitroso Compounds in the Presence of Hydrogen Peroxide

et al. 2016

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Dedicatedi nm emory of Prof.Y iannis Elemes,r emembering the stimulating scientific discussionsa nd friendship.Supporting information for this article is availableonthe WWW under http://dx.doi.org/10.1002/adsc.201500957.Abstract: In this article,t he catalytic activity of titania-supported gold nanoparticles (Au/TiO 2 )w as studied for the selective oxidation of aminesi nto nitroso compounds using hydrogen peroxide (H 2 O 2 ). Gold nanoparticles deposited on DegussaP 25 polymorphso ft itania (TiO 2 )h ave been found to promote the selective formation of av ariety of nitroso arenes in high yields and selectivities,e ven in al arge-scale synthesis. In contrast, alkyl amines are oxidized to the corresponding oximes under the examined conditions.K inetic studies indicated that aryl amines substituted with electron-donating groups are oxidized faster than the corresponding amines bearing an electron-withdrawing functionality.AHammett-type kinetic analysiso farange of para-X-substituteda ryl aminesi mplicates an electront ransfer (ET) mechanism (1 = À1.15) for oxidation reactions with concomitant formation of the corresponding Naryl hydroxylamine as possible intermediate.W ea lso show that the oxidation protocolo fa ryl amines in the presence of 1,3-cyclohexadiene leads in excellent yields to the corresponding hetero Diels-Alder adducts between the diene andthe in situ formed nitrosoarenes.

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Effects of bleomycin and antioxidants on the fatty acid profile of testicular cancer cell membranes

Çört

Özben

Melchiorre

et al. 2016

Biochimica et Biophysica Acta (BBA) - Biomembranes

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Bleomycin is used in chemotherapy regimens for the treatment of patients having testicular germ-cell tumor (TGCT). There is no study in the literature investigating the effects of bleomycin on membrane lipid profile in testicular cancer cells. We investigated membrane fatty acid (FA) profiles isolated, derivatized and analyzed by gas chromatography of NTera-2 testicular cancer cells incubated with bleomycin (Bleo) for 24 h in the absence and presence of N-Acetyl-L-Cysteine (NAC) and curcumin (Cur) as commonly used antioxidant adjuvants. At the same time the MAPK pathway and EGFR levels were followed up. Bleomycin treatment increased significantly saturated fatty acids (SFA) of phospholipids at the expense of monounsaturated (MUFA) and polyunsaturated fatty acids (PUFA). Bleomycin also led to a significant increase in the trans lipid isomers of oleic and arachidonic acids due to its free radical producing effect. Incubation with bleomycin increased the p38 MAPK and JNK levels and downregulated EGFR pathway. Coincubation of bleomycin with NAC reversed effects caused by bleomycin. Our results highlight the important role of membrane fatty acid remodeling occurring during the use of bleomycin and its concurrent use with antioxidants which can adjuvate the cytotoxic effects of the chemotherapeutic agents.

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Biomimetic chemistry on the protection of cis phospholipid from the thiyl radical isomerization by common antioxidants

Cited by 7 publications

References 41 publications

The Reaction of Thiyl Radical with Methyl Linoleate: Completing the Picture

The Reaction of Thiyl Radical with Methyl Linoleate: Completing the Picture

Titania‐Supported Gold Nanoparticles Catalyze the Selective Oxidation of Amines into Nitroso Compounds in the Presence of Hydrogen Peroxide

Effects of bleomycin and antioxidants on the fatty acid profile of testicular cancer cell membranes

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