Identification, synthesis, and safety assessment of forchlorfenuron (1-(2-chloro-4-pyridyl)-3-phenylurea) and its metabolites in kiwifruits

Identification and evaluation of safety of forchlorfenuron ((1-(2-chloro-4-pyridyl)-3-phenylurea)), 1, metabolites after biotransformation in kiwifruit is the objective of this study. To elucidate properties of these metabolites, liquid chromatography hybrid ion trap time-of-flight mass spectrometry (LC-IT-TOF-MS) was applied, with MetID Solution and Formula Predictor Software in positive mode. Cytotoxicity of forchlorfenuron and its metabolites were tested through sulforhodamine B assays against normal Chinese hamster ovary cells (CHO). As deduced from characteristic fragment ions of forchlorfenuron, then confirmed by comparison with synthetic standards, as well as characterized by NMR and mass spectrometry techniques, results indicate the presence of 4-hydroxyphenyl-forchlorfenuron, 2, 3-hydroxyphenyl-forchlorfenuron, 3, and forchlorfenuron-4-O-β-D-glucoside, 5. Forchlorfenuron (IC50 = 12.12 ± 2.14 μM) and 4-hydroxyphenyl-forchlorfenuron (IC50 = 36.15 ± 1.59 μM), exhibits significant cytotoxicity against CHO, while 3-hydroxyphenyl-forchlorfenuron and forchlorfenuron-4-O-β-D-glucoside show no cytotoxicity.