Screening and Identification of Potential Abscisic Acid Catabolites by Chemical Labeling-Assisted...

In this study, a screening strategy was established based on ultrahigh-performance liquid chromatography coupled with high-resolution mass spectrometry assisted by chemical isotope labeling (CIL-UPLC-HRMS) for screening and identifying abscisic acid (ABA) catabolites. Based on the structures of known ABA catabolites, this strategy first proposed the structures of catabolites to be discovered. Afterward, a pair of isotope reagents N,N-2-dimethylaminoethylamine (DMED) and d₄-DMED were used as labeling reagents to label the carboxyl groups in ABA and its catabolites. Then, the mass-to-charge ratio (m/z) of DMED- and d₄-DMED-labeled ABA catabolites was calculated based on the labeling schema. In light of the characteristic fragmentation patterns of the DMED-labeled standards of ABA and its catabolites, screening criteria were formulated. Using our strategy, ABA, t-ABA, and 18 ABA catabolites were identified from seven plant samples. Of the identified catabolites, 16 were known, and to our knowledge, 2 were previously unidentified. Our findings contribute to ABA catabolic network improvement.