Abstract:Sulfenic acids react as both nucleophiles and electrophiles, which may be attributable to interconversion between sulfenyl and sulfinyl tautomers. We demonstrate one-pot trapping of both tautomeric forms of glutathione sulfenic acid by LCMS. The sulfinyl tautomers are characterized by reaction with nucleophilic reagents such as dimedone and cyanide, giving unique products that are analogous to corresponding adducts of aldehydes. Likewise, we show that aldehyde reactive reagents such as silyl enol ethers also r… Show more
“…In a recent report, we demonstrated that the sulfenyl and sulfinyl tautomeric forms, Scheme 3, of glutathione sulfenic acids can be trapped by various C-type nucleophilic traps like dimedone, 1-trimethylsiloxycyclohexene, and cyanide [39]. The dual reactivity of sulfenic acid as nucleophile and electrophile towards trapping agents produced unique products that are well characterized by LC/HDMS studies.…”
Glutathione-based products, GSnX, of the reaction of hydrogen sulfide, H2S, S-nitroso glutathione, and GSNO, at varied stoichiometries have been analyzed by liquid chromatography high-resolution mass spectrometry (LC-HRMS) and chemical trapping experiments. A wide variety of glutathione-based species with catenated sulfur chains have been identified including sulfanes (GSSnG), sulfides (GSSnH), and sulfenic acids (GSnOH); sulfinic (GSnO2H) and sulfonic (GSnO3H) acids are also seen in reactions exposed to air. The presence of each species of GSnX within the original reaction mixtures was confirmed using Single Ion Chromatograms (SICs), to demonstrate the separation on the LC column, and given approximate quantification by the peak area of the SIC. Further, confirmation for different GSnX families was obtained by trapping with species-specific reagents. Several unique GSnX families have been characterized, including bridging mixed di- and tetra-valent polysulfanes and internal trithionitrates (GSNHSnH) with polysulfane branches. Competitive trapping experiments suggest that the polysulfane chains are formed via the intermediacy of sulfenic acid species, GSSnOH. In the presence of radical trap vinylcyclopropane (VCP) the relative distributions of polysulfane speciation are relatively unaffected, suggesting that radical coupling is not a dominant pathway. Therefore, we suggest polysulfane catenation occurs via reaction of sulfides with sulfenic acids.
“…In a recent report, we demonstrated that the sulfenyl and sulfinyl tautomeric forms, Scheme 3, of glutathione sulfenic acids can be trapped by various C-type nucleophilic traps like dimedone, 1-trimethylsiloxycyclohexene, and cyanide [39]. The dual reactivity of sulfenic acid as nucleophile and electrophile towards trapping agents produced unique products that are well characterized by LC/HDMS studies.…”
Glutathione-based products, GSnX, of the reaction of hydrogen sulfide, H2S, S-nitroso glutathione, and GSNO, at varied stoichiometries have been analyzed by liquid chromatography high-resolution mass spectrometry (LC-HRMS) and chemical trapping experiments. A wide variety of glutathione-based species with catenated sulfur chains have been identified including sulfanes (GSSnG), sulfides (GSSnH), and sulfenic acids (GSnOH); sulfinic (GSnO2H) and sulfonic (GSnO3H) acids are also seen in reactions exposed to air. The presence of each species of GSnX within the original reaction mixtures was confirmed using Single Ion Chromatograms (SICs), to demonstrate the separation on the LC column, and given approximate quantification by the peak area of the SIC. Further, confirmation for different GSnX families was obtained by trapping with species-specific reagents. Several unique GSnX families have been characterized, including bridging mixed di- and tetra-valent polysulfanes and internal trithionitrates (GSNHSnH) with polysulfane branches. Competitive trapping experiments suggest that the polysulfane chains are formed via the intermediacy of sulfenic acid species, GSSnOH. In the presence of radical trap vinylcyclopropane (VCP) the relative distributions of polysulfane speciation are relatively unaffected, suggesting that radical coupling is not a dominant pathway. Therefore, we suggest polysulfane catenation occurs via reaction of sulfides with sulfenic acids.
“…1 . The electrophilic and nucleophilic characteristics of HSOH is also evident in its reaction with 1-trimethylsiloxycyclohexene ( S4 ), which yields unique products analogous to those seen in glutathione peroxidations [33] . Fig.…”
Section: Sulfenic Acid Hsohmentioning
confidence: 99%
“…These SOS are highly reactive and notoriously difficult to characterize in biologically relevant conditions, and unlike their alkyl homologs, there is a little data on SOS generation and speciation during H 2 S oxidation [29] , [30] , [31] , [32] . We recently reported trapping of both sulfenyl and sulfinyl tautomers of oxidized glutathione derivatives using a combination of selective nucleophilic and electrophilic trapping reagents and characterization by high resolution LC MS [33] . We hypothesize that the physiological effect of H 2 S may derive from SOS, and thus we investigated their formation in biologically relevant conditions using similar methods, in situ derivatization with nucleophilic sulfenyl trapping reagent dimedone [34] , [35] and electrophilic reagents iodoacetamide, as well as mono- and di-bromobimane [36] .…”
Section: Introductionmentioning
confidence: 99%
“…The generated SOS were derivatized by reaction with nucleophilic traps such as dimedone (DH) and 1-trimethylsiloxycyclohexene [33] , as well as electrophilic traps such as iodoacetamide (IA), and mono- or di-bromobimane (BrB and Br 2 B). In a standard experiment, 1 mM Na 2 S dissolved in pH 7 iP buffer was reacted with 1.2 mM of maleic peroxide, a soft oxidant formed in situ by mixing H 2 O 2 with maleic anhydride; five minutes after reaction initiation, a 5 fold excess of trapping reagents are added [37] .…”
Small oxoacids of sulfur (SOS) are elusive molecules like sulfenic acid, HSOH, and sulfinic acid, HS(O)OH, generated during the oxidation of hydrogen sulfide, H2S, in aqueous solution. Unlike their alkyl homologs, there is a little data on their generation and speciation during H2S oxidation. These SOS may exhibit both nucleophilic and electrophilic reactivity, which we attribute to interconversion between S(II) and S(IV) tautomers. We find that SOS may be trapped in situ by derivatization with nucleophilic and electrophilic trapping agents and then characterized by high resolution LC MS. In this report, we compare SOS formation from H2S oxidation by a variety of biologically relevant oxidants. These SOS appear relatively long lived in aqueous solution, and thus may be involved in the observed physiological effects of H2S.
“…It is quite reactive, and can undergo a multitude of reactions resulting in a wide variety of chemical species. For example, sulfenic acid can undergo further oxidations to more stable metabolites (such as sulfinic and sulfonic acids), react with another sulfenic acid (disproportionation reaction) to form a free thiol and a sulfinic acid, react with nucleophiles (like thiols) resulting in mixed disulfides [ 13 ], react with cyanide (resulting in thiocyanate), react with thiocyanate (resulting in dithiocyanate) [ 14 ], or even react with nucleophilic moieties of proteins, commonly with cysteine residues, to form covalent adducts [ 11 ]. Due to this highly reactive behavior of sulfenic acid intermediates, detection is especially challenging.…”
In some cases, the formation of reactive species from the metabolism of xenobiotics has been linked to toxicity and therefore it is imperative to detect potential bioactivation for candidate drugs during drug discovery. Reactive species can covalently bind to trapping agents in in vitro incubations of compound with human liver microsomes (HLM) fortified with β-nicotinamide adenine dinucleotide phosphate (NADPH), resulting in a stable conjugate of trapping agent and reactive species, thereby facilitating analytical detection and providing evidence of short-lived reactive metabolites. Since reactive metabolites are typically generated by cytochrome P450 (CYP) oxidation, it is important to ensure high concentrations of trapping agents are not inhibiting the activities of CYP isoforms. Here we assessed the inhibitory properties of fourteen trapping agents against the major human CYP isoforms (CYP1A2, 2C9, 2C19, 2D6 and 3A). Based on our findings, eleven trapping agents displayed inhibition, three of which had IC50 values less than 1 mM (2-mercaptoethanol, N-methylmaleimide and N-ethylmaleimide (NEM)). Three trapping agents (dimedone, N-acetyl-lysine and arsenite) did not inhibit CYP isoforms at concentrations tested. To illustrate effects of CYP inhibition by trapping agents on reactive intermediate trapping, an example drug (ticlopidine) and trapping agent (NEM) were chosen for further studies. For the same amount of ticlopidine (1 μM), increasing concentrations of the trapping agent NEM (0.007–40 mM) resulted in a bell-shaped response curve of NEM-trapped ticlopidine S-oxide (TSO-NEM), due to CYP inhibition by NEM. Thus, trapping studies should be designed to include several concentrations of trapping agent to ensure optimal trapping of reactive metabolites.
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