Methodologies for the analysis of reduced and oxidized N‐acetylcysteine in biological systems

Publisher Website
Google Scholar
Abstract
A rapid and sensitive assay is described for both reduced and oxidized N‐acetylcysteine in biological matrices. Free, reduced N‐acetylcysteine is derivatized, along with any endogenous free thiols, in situ by treatment of the samples with the membrane‐permeable, thiol‐reactive agent monobromobimane. The N‐acetylcysteine‐monobromobimane adduct thus formed is analysed by high performance liquid chromatography with fluorescence detection. Oxidized N‐acetylcysteine is released from disulfides by in situ treatment of the samples with dithiothreitol, rendering the total N‐acetylcysteine content of the system available for derivatization and analysis. The conditions of derivatization ensured 100 per cent recovery of N‐acetylcysteine as the monobromobimane adduct, and calibration curves were linear over the range 0.1 μM to 1.0mM N‐acetylcysteine. The precision of the assay procedures was 97 per cent over this range. These assay procedures have been applied to studies of the pharmacokinetics of N‐acetylcysteine following single oral and intravenous administrations of the drug to a single human volunteer.