Qualitative and Quantitative Analyses of 1-Aminocyclopropane-1-carboxylic Acid Concentrations in Plants Organs Using...

1-Aminocyclopropane-1-carboxylic acid (ACC) is a direct precursor of phytohormone ethylene. We used a phenyl isothiocyanate (PITC) derivatization modification method combined with spectrographic analysis to isolate and identify three products of the derivatization reactions of ACC and PITC. The MRM⁺ mode of UPLC-MS/MS was used to establish the analysis of 6-phenyl-5-thioxo-4,6-diazaspiro[2.4]heptan-7-one (PTH-ACC). Three fragment ions detected at the precursor ion (m/z 219.10) were selected for qualitative analysis (m/z 98.10, 77.15, and 72.10), and the most abundant product ion (m/z 98.10) was selected for quantitative analysis. The conditions for the derivatization reaction for the main product PTH-ACC were analyzed and optimized using response surface methodology, resulting in the optimal derivatization conditions being a reaction temperature of 90 °C, a reaction time of 1.5 h, and a formic acid (FA) concentration of 40%. ACC concentrations in 25-200 mg rice samples was successfully determined. Moreover, the ACC concentrations in the shoots, seeds, and roots of rice, maize, and cotton seedlings were all analyzed. The ACC concentrations were found to exhibit tissue specificity. Interestingly, during the ripening process in tomato and mango fruits, the concentrations of ACC in the fruits showed an initial increase, followed by a decrease. In black nightshade fruits, ACC content was the highest in the immature stage, decreased with fruit ripening, and remained stable from the semimature to mature stages. These results provide a reliable analysis technology foundation for the study of ethylene.