Identification of N-Acetyl-S-(3-Cyano-2-(Methylsulfanyl)Propyl-Cysteine as a Major Human Urine Metabolite from the Epithionitrile 1-Cyano-2,3-Epithiopropane, the Main Glucosinolate Hydrolysis Product from Cabbage

Abstract

Brassica vegetables such as cabbage or pak choi contain alkenyl glucosinolates which can release epithionitriles and to a lesser degree isothiocyanates upon enzymatic hydrolysis. Here, for the first time, the metabolism of an epithionitrile was investigated in humans, namely 1-cyano-2,3-epithiopropane (CETP). After consumption of Brassica oleracea var. capitata f. alba and Brassica carinata sprouts, the main urinary metabolite of CETP was identified as N-acetyl-S-(3-cyano-2-(methylsulfanyl)propyl-cysteine using an UHPLC-ESI-QToF-MS approach and synthesis of the metabolite. This urinary epithionitrile metabolite is an S-methylated mercapturic acid. No other metabolites were detected. Then, in a preliminary pilot experiment the excretion kinetics of CETP were investigated in three volunteers. After consumption of a B. carinata sprout preparation containing 50.8 µmol of CETP, urinary N-acetyl-S-(3-cyano-2-(methylsulfanyl)propyl-cysteine concentrations were the highest three hours after consumption, ranging from 23.9 to 37.2 µM, and declined thereafter. Thus, epithionitriles are bioavailable compounds that are metabolized similarly to isothiocyanates by the mercapturic acid pathway. In the future, more epithionitrile metabolites should be identified and the pharmacokinetics of these important class of dietary compounds should be assessed in more detail

Identification and Characterization of Three Epithiospecifier Protein Isoforms in Brassica oleracea

“…Occurrence and activity of the epithiospecifier protein (ESP) leads to the generation of ETNs from alkenyl-GLS aglucons as well as nitriles from non-alkenyl-GLS-aglucons (Burow et al, 2006;Matusheski et al, 2006). Many Brassica species release nitriles and ETNs upon GLS hydrolysis, among them B. oleracea and also B. campestris, B. carinata, and B. rapa (Macleod and Rossiter, 1985;Matusheski et al, 2004;Hanschen and Schreiner, 2017;Klopsch et al, 2017;Klopsch et al, 2018;Hanschen et al, 2019). So far, ESPs were characterized in A. thaliana (Lambrix et al, 2001;De Torres Zabala et al, 2005;Hanschen et al, 2018b) and in Brassica species, such as broccoli (B. oleracea var.…”

Metabolism and Recovery of Epithionitriles from Glucosinolates—A Human Intervention Study

“…In the previous study, the reported range of Me‐CETP‐ N ‐Ac‐Cys concentrations was 24−37 µmol L ‐1 in urine samples, 180 min after sprout consumption with a 1.26‐fold higher dose of CETP given compared to the present study. [ 15 ] Here, concentration of five spot urines in the range of 160−190 min varied from 2.7 to 19 µmol L −1 (average 8.0 ± 6.5 µmol L −1 ), therefore being in a similar range but lower. This might be caused by a different drinking behavior as many of the participants in the present study drank frequently resulting in many spot urine samples and those had lower concentrations compared to participants with few urine donations (compare Figure S2, Supporting Information).…”

“…Recently, Me‐CETP‐ N ‐Ac‐Cys was identified as a human CETP metabolite in urine samples. [ 15 ] In the present study we investigated the bioavailability and metabolism of the ETNs CETP, CETB, and CETPent in a human intervention study.…”

“…Therefore, similarly to the metabolism of ITCs, [ 14 ] in humans and rodents ETNs seem to be conjugated with GSH and metabolized via the mercapturic acid pathway. [ 12,13,15 ]…”

“…Therefore, similarly to the metabolism of ITCs, [14] in humans and rodents ETNs seem to be conjugated with GSH and metabolized via the mercapturic acid pathway. [12,13,15] So far, there is no information on the bioavailability and pharmacokinetics of ETNs. Therefore, it was the aim of this study to evaluate metabolism and excretion kinetics of the three ETNs CETP, CETB, and CETPent in intervention studies with white cabbage sprouts beverage (CETP-rich) and pak choi sprouts beverage (CETB-and CETPent-rich).…”