Bile acids: Electrochemical oxidation on bare electrodes after acid-induced dehydration

Klouda, Jan; Barek, Jiřı́; Kočovský, Pavel; Herl, Thomas; Matysik, Frank‐Michael; Nesměrák, Karel; Schwarzová‐Pecková, Karolina

doi:10.1016/j.elecom.2017.11.024

Cited by 13 publications

(7 citation statements)

References 23 publications

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“…The proposed mechanism of TIB is similar to the one described for the electrochemical oxidation of chenodeoxycholic acid using BDD as the working electrode. Chenodeoxycholic acid is a cholesterol‐derived structure similar to TIB [45] …”

Section: Resultsmentioning

confidence: 99%

“…The mechanism was suggested to be an oxidation process that occurs at + 1.38 V in the double bound of this molecule through one-electron transfer resulting of a pHindependent radical cation ( Figure 3A). As described in the literature, [45] the generated radical cation, in the presence of an aprotic solvent (acetonitrile; added to supporting electrolyte for better solubilization of TIB), can be rationalized by the Ritter reaction. [45] In this reaction, the Lewis basic nitrogen of acetonitrile attacks cationic species followed by hydrolysis.…”

Section: Electrochemical Behavior Of Tibolone (Tib)mentioning

confidence: 97%

“…As described in the literature, [45] the generated radical cation, in the presence of an aprotic solvent (acetonitrile; added to supporting electrolyte for better solubilization of TIB), can be rationalized by the Ritter reaction. [45] In this reaction, the Lewis basic nitrogen of acetonitrile attacks cationic species followed by hydrolysis. So, a second oxidation process (at + 1.60 V; Figure 3B) with a loss of one electron leads to a carbocation, and the second oxidation product is obtained.…”

Section: Electrochemical Behavior Of Tibolone (Tib)mentioning

confidence: 97%

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Electrochemical Determination of the Steroid Tibolone and Its Metabolites in Saliva Samples

et al. 2020

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Tibolone (TIB) is a synthetic steroid banned by the World Anti‐Doping Agency (WADA) due to its similar properties to estrogen and progesterone. In this work, a simple and low‐cost electrochemical method for the determination of TIB and its metabolites (3‐α hydroxytibolone and 3‐β hydroxytibolone) in authentic human saliva is reported. Square‐wave voltammetry (SWV) with an unmodified boron‐doped diamond (BDD) electrode and phosphate buffer 0.1 mol L−1 were selected as the electrochemical technique, working electrode, and supporting electrolyte, respectively. Analytical characteristics of the proposed method include good repeatability (RSD <2.4 %), wide linear range (1 to 110 μmol L−1; r=0.999) and low detection limit (0.3 μmol L−1). Average recovery values (104±3 % for TIB and 98±5 % for the metabolites) for direct analysis of spiked saliva samples (only diluted in supporting electrolyte) indicate that no significant matrix interference was observed. The proposed method was also efficient for the determination of TIB in pharmaceutical samples (statistically similar results to those obtained by HPLC).

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Section: Resultsmentioning

confidence: 99%

Section: Electrochemical Behavior Of Tibolone (Tib)mentioning

confidence: 97%

Section: Electrochemical Behavior Of Tibolone (Tib)mentioning

confidence: 97%

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Electrochemical Determination of the Steroid Tibolone and Its Metabolites in Saliva Samples

et al. 2020

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“…Similar results were also described in the literature for the electrochemical oxidation of cholesterol (as they used a solution of cholesterol in 90% MeOH containing 20 mmol/L ammonium formate) [ 28 ]. The use of perchloric acid as an oxidation reagent for promoting electrochemical oxidation did not increase the oxidation rate, as described in the literature [ 31 ]. However, it should be noted that the resulting oxidation products in recent studies were not measured via a mass spectrometer, but only through measuring the corresponding current.…”

Section: Discussionmentioning

confidence: 97%

“…Steroid compounds and bile acids are electrochemically active only under specific conditions and the use of specific electrode material (e.g., mercury-based electrodes, or modified glassy carbon electrodes) [ 30 ]. A current study presented an approach of an anodic electrochemical oxidation of bile acids by activating the saturated steroid core by introducing double bonds via dehydration [ 31 ]. None of the studies so far determined the resulting oxidation products of the bile acids.…”

Section: Introductionmentioning

confidence: 99%

Electrochemical Oxidation of Primary Bile Acids: A Tool for Simulating Their Oxidative Metabolism?

Suarez

Rohn

2018

IJMS

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Bile acids are a subgroup of sterols and important products of cholesterol catabolism in mammalian organisms. Modifications (e.g., oxidation and 7-dehydroxylation) are predominantly exerted by the intestinal microbiota. Bile acids can be found in almost all living organisms, and their concentration and metabolism can be used for the assessment of the pathological and nutritional status of an organism. Electrochemical oxidation is a rapid, relatively inexpensive approach to simulate natural metabolic redox processes in vitro. This technique further allows the identification of oxidative degradation pathways of individual substances, as well as the demonstration of binding studies of generated oxidation products with biologically relevant molecules. When coupling an electrochemical and a high-resolution mass spectrometric system, oxidation products can be generated and identified directly by non-targeted ESI-MS. Here, a method for the generation of oxidation products of the primary bile acids cholic acid and chenodeoxycholic acid was exemplarily developed. Most products and the highest intensities were observed at a pH value of 6. For cholic acid, a high potential of 3 V was necessary, while for chenodeoxycholic acid, a potential of 2.4 V led to a higher number of oxidation products. In a second approach, a binding study with glutathione was performed to simulate phase II metabolism. It was possible to detect signals of free glutathione, free bile acids, and adducts of both reactants. As the resulting mass spectra also showed some new signals of the oxidized bile acid, which could not be observed without glutathione, it can be assumed that glutathione is able to bind reactive oxidation species before reacting with other products.

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Addition Reactions: Polar Addition

Kočovský

2021

Organic Reaction Mechanisms Series

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Bile acids: Electrochemical oxidation on bare electrodes after acid-induced dehydration

Cited by 13 publications

References 23 publications

Electrochemical Determination of the Steroid Tibolone and Its Metabolites in Saliva Samples

Electrochemical Determination of the Steroid Tibolone and Its Metabolites in Saliva Samples

Electrochemical Oxidation of Primary Bile Acids: A Tool for Simulating Their Oxidative Metabolism?

Addition Reactions: Polar Addition

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