Occurrence of the Plant Growth Regulator Chlormequat in Food May Be Due to Natural Formation: A Preliminary Mechanistic Study

Abstract

The study reports the role of choline and compounds thereof in the formation of chlormequat under thermal conditions, with emphasis on the molecular mechanism involved in the transformation. The data show the decomposition of choline to chlormequat at 200 °C in presence of chloride ions, likely by nucleophilic substitution. Furthermore, the results suggest that phosphatidylcholine, glycerophosphocholine, and phosphocholine are the effective precursors of chlormequat under sufficient thermal conditions due to their capability to degrade to choline and/or the ability of the phosphate moiety to behave as a good leaving group with respect to nucleophilic attacks. Thermal treatments (120 and 200 °C) applied to egg powder, rich in phosphatidylcholine, and wheat flour, with choline at a substantial level, suggest that less energy is required for obtaining chlormequat from phosphatidylcholine than from choline. This observation is consistent with the postulated mechanism of a nucleophilic substitution with phosphate moieties acting as better leaving groups than the hydroxyl group.

A pilot study of chlormequat in food and urine from adults in the United States from 2017 to 2023

“…Although there is no monitoring of chlormequat in food products in the U.S., and no historical data available for concentrations of chlormequat in foods sold in the U.S., we suspect these exposures were likely dietary given the short half-life of chlormequat. Additionally, natural formation of chlormequat from choline precursors in wheat products and egg powder has been shown to occur under high temperatures such as those used during food processing and production, resulting in chlormequat concentrations between 5 and 40 ng/g [ 21 ]. Our food testing results indicate chlormequat levels in some samples, including one organic oat-based product, were similar to those reported in the study of naturally forming chlormequat, while many other samples were higher.…”

Risk of de‐novo formation of chlormequat and mepiquat in industrial cocoa products assessed by ion chromatography coupled with high‐resolution mass spectrometry

“…(2020) evaluating the role of choline in its formation under thermal conditions (200 °C). The formation of CQ was also documented in wheat flour and egg powder after cooking (Yuan et al ., 2017; Eriksen et al ., 2020).…”

“…The natural formation of CQ was also investigated in dark barley malts (Ekielski et al ., 2018), and the chemical mechanism was explained by Eriksen et al . (2020) evaluating the role of choline in its formation under thermal conditions (200 °C). The formation of CQ was also documented in wheat flour and egg powder after cooking (Yuan et al ., 2017; Eriksen et al ., 2020).…”