Identification of Metabolites of [1,2,3-¹³C]Propargyl Alcohol in Mouse Urine by ¹³C NMR and Mass Spectrometry and Comparison to Rat

Abstract

Species differences in the metabolism of acetylenic compounds commonly used in the formulation of pharmaceuticals and pesticides have not been investigated. To better understand the in vivo reactivity of this bond, the metabolism of propargyl alcohol (PA), 2-propyn-1-ol, was examined in rats and mice. An earlier study (Banijamali, A. R.; Xu, Y.; Strunk, R. J.; Gay, M. H.; Ellis, M. C.; Putterman, G. J. J. Agric. Food Chem. 1999, 47, 1717-1729) in rats revealed that PA undergoes extensive metabolism primarily via glutathione conjugation. The current research describes the metabolism of PA in CD-1 mice and compares results for the mice to those obtained for rats. [1,2,3-(13)C;2,3-(14)C]PA was administered orally to the mice. Approximately 60% of the dose was excreted in urine by 96 h. Metabolites were identified, directly, in whole urine by 1- and 2-D (13)C NMR and HPLC/MS and by comparison with the available reference compounds. The proposed metabolic pathway involves glucuronide conjugation of PA to form 2-propyn-1-ol-glucuronide as well as oxidation of PA to the proposed intermediate 2-propynal. The aldehyde undergoes conjugation with glutathione followed by further metabolism to yield as final products 3,3-bis[(2-acetylamino-2-carboxyethyl)thio]-1-propanol, 3-[(2-acetylamino-2-carboxyethyl)thio]-3-[(2-amino-2-carboxyethyl)thi o]-1-propanol, 3,3-bis[(2-amino-2-carboxyethyl)thio]-1-propanol, 3-[(2-amino-2-carboxyethyl)thio]-2-propenoic acid, and 3-[(2-formylamino-2-carboxyethyl)thio]-2-propenoic acid. A small portion of 2-propynal is also oxidized to result in the excretion of 2-propynoic acid. On the basis of urinary metabolite data, qualitative and quantitative differences are noted between rats and mice in the formation of the glucuronide conjugate of PA and in the formation of 2-propynoic acid and metabolites derived from glutathione. These metabolites represent further variation on glutathione metabolism following its addition to the carbon-carbon triple bond compared to those described for the rat.

A mechanism for the formation of bis‐glutathione conjugates of propargyl alcohol

“…To better understand the in vivo reactivity of propargyl alcohol, we previously investigated its metabolism in rats and mice 2. 3 In those studies, a mixture of 13 C‐ and 14 C‐propargyl alcohol was administered to rats and mice, and urinary metabolites were characterized by HPLC, mass spectrometry and NMR spectroscopy (Fig 1). Metabolites identified in these studies included 3,3‐bis[(2‐acetylamino‐2‐carboxyethyl)thio]‐1‐propanol ( I ), 3‐[(2‐acetylamino‐2‐carboxyethyl)sulfinyl]‐3‐[(2‐acetylamino‐2‐carboxyethyl)thio]‐1‐propanol ( II ), 3,3‐bis[(2‐amino‐2‐carboxyethyl)thio]‐1‐propanol ( III ), 3‐[(2‐acetylamino‐2‐carboxyethyl)thio]‐3‐[(2‐amino‐2‐carboxyethyl)thio]‐1‐propanol ( IV ), 3‐[(2‐amino‐2‐carboxyethyl)thio]‐2‐propenoic acid ( V ), 3‐(carboxymethylthio)‐2‐propenoic acid ( VI ), 3‐[(2‐formylamino‐2‐carboxyethyl)thio]‐2‐propenoic acid ( VII ), 3‐(methylsulfinyl)‐2‐(methylthio)‐2‐propenoic acid ( VIII ), 2‐propynoic acid ( IX ) and propargyl alcohol glucuronide ( X ).…”

“…Using a chemical approach, this study was designed to determine the precise pathway involved in the formation of the bis‐glutathione conjugates of propargyl alcohol that had previously been identified in rat and mouse urine 2. 3, 6 For this purpose rats were administered a mixture of [2,3‐ 14 C]propargyl alcohol and [3‐ 2 H 2 ]propargyl alcohol. Mass spectrometry and synthetic standards of the unlabeled material were used to determine the number of deuteriums retained in the isolated bis‐conjugate (Fig 1, metabolite I ), providing the key to understanding mechanism of formation.…”