Preparation of [1'-13 C]citric acid as a probe in a breath test to evaluate tricarboxylic acid cycle flux

Abstract

[1'-¹³ C]Citric acid (1) was efficiently prepared from dimethyl 1,3-acetonedicarboxylate in two steps as a probe for a breath test. The synthetic method was selected because of the yield and reproducibility. Compound 1 was orally administrated to rats, and the time course of the increase of ¹³ CO₂ /¹² CO₂ ratios (Δ¹³ CO₂ ) in their breath was successfully followed, indicating the metabolism of 1. Thus, the ¹³ C-breath test using 1 is a promising method to evaluate tricarboxylic acid (TCA) cycle flux.

Keywords: TCA cycle; breath test; carbon-13; citric acid; stable label.