Uptake, Translocation, and Metabolism of ¹⁴C-Quinotrione in Pak Choi

Few studies have examined the environmental fate of quinotrione, a new type of 4-hydroxyphenylpyruvate dioxygenase (HPPD)-inhibiting herbicide in plants. In this study, the uptake, translocation, and metabolism of quinotrione in pak choi were explored using ¹⁴C-labeling method and high-resolution mass spectrometry. The results showed that 57.7% of ¹⁴C-quinotrione was accumulated by pak choi via foliar application. The ¹⁴C-quinotrione concentration in the leaves (444.0 mg kg^-1) at 5 d was 20 times higher than that in the roots (22.3 mg kg^-1). The parent compound was the dominant residues (44.5-57.0%), while five metabolites were identified. Among these, hydroxylated quinotrione emerged as a key intermediate, with another three metabolites formed through hydrolysis, reduction, and oxidation. Notably, 6-(2,6-dioxocyclohexane-1-carbonyl)-1-methylquinazoline-2,4(1H,3H)-dione was the most abundant metabolite (17.7-22.2%). Our study provides further insight into the uptake and metabolism of HPPD herbicides in pak choi and the assessment of the environmental risk and food safety of quinotrione.