Transformation products elucidation of forchlorfenuron in postharvest kiwifruit by time-of-flight mass spectrometry

Forchlorfenuron (1-(2-chloro-4-pyridyl)-3-phenylurea, FCF) is a plant growth regulator, being extensively used for increasing kiwifruit size. The toxicological properties of its may persist in their transformation products (TPs) or even higher toxicity than FCF. TPs elucidation of FCF in postharvest kiwifruit (Actinidia chinensis, Chinese gooseberry) by the liquid chromatography ionization hybrid ion trap and time-of-flight mass spectrometry (LC-ESI-IT-TOF/MS) in positive mode was the objective of the present study. Fifteen days after full bloom, kiwifruits were dipped for 5s with high dosage FCF solution (60 mg/L), so that sufficient peaks could be detected. The chemical structure of unknown TPs was analyzed in combination of functions of LCMS-IT-TOF, such as high-accurate MSn, formula predictor, metabolite structural analysis software MetID Solution, profiling solution metabolomics software, and neutral loss, characteristic isotopic patterns of chlorine, the fragmentation pattern and retention time of standard substances, nitrogen rule, chemical components of kiwifruit. Total 17 TPs were detected via comparisons of their accurate MSn data of commercial analytical standards and synthesized standards with high purity, such as 4-amino-2-chloropyridine, phenylurea, 2-hydroxy-FCF, 1-(2-chloro-6-((3, 4, 5-trihydroxy-6-(hydroxymethyl) tetrahydro-2H-pyran-2-yl) oxy) pyridin-4-yl)-3-phenylurea, 1, 3-bis (2-chloropyridin-4-yl) urea, 1,3-diphenylurea, 1-(2-chloropyridin-4-yl)urea, FCF-2-O-β-D-glucoside, and so on. The major transformation pathways of FCF in kiwifruit were biochemical and photochemical cleavage pathway. The experimental results indicate that LCMS-IT-TOF is powerful and effective tool for identification of FCF TPs.