Chemical change and mechanism of Millettia speciosa with sulfur fumigation by UHPLC-QTOF-MS/MS

Millettia speciosa Champ. (MSCP), which is distributed and used in Southern China, is often sulfur-fumigated during postharvest handling to prevent insects and molds. In the present study, a comprehensive strategy was proposed by using ultrahigh-performance liquid chromatography-quadrupole/time-of-flight mass spectrometry (UHPLC-QTOF-MS/MS) with multivariate analysis to rapidly identify potential chemical sulfur-fumigated MSCP (SF-MSCP) samples, discover chemical transformation mechanisms and control the quality of SF-MSCP. Eighty-six compounds were tentatively assigned, and ten compounds were screened out as potential markers. Moreover, the chemical transformation mechanism was deduced by hydrolysis, esterification and dehydration reactions that occurred during the sulfur-fumigated process. The developed method was successfully applied to predict 16 commercial MSCP samples, and 9 samples were found to contain sulfur compounds, ranging in sulfur residues from 100 to 310 mg/kg. These research outcomes can not only be used to distinguish the nonfumigated MSCP from SF-MSCP by chemical markers but also provide a chemical basis for further comprehensive investigating in-depth safety and functional evaluations of SF-MSCP.