Objective To develop an effective method for characterizing tannin of Chinese gallnut by ultra-performance liquid chromatography–quadrupole time of flight mass spectrometry (UHPLC–QTOF–MS), and analyze the fragmentation behavior of gallotannins.

MethodsHigh temperature and ultrasonic–assisted methods were implemented for extracting phenolic compounds from Chinese gallnut, and the fragmentation pathway of gollotannins were characterized by MS/MS spectrometry.

ResultsA total of 20 compounds were identified, including 14 gallotannins, 2 gallagyl esters, 3 phenolic acids, and 1 flavanol. Gallotannins with molecular mass higher than 1500 Da were not identified when high temperature 121 ℃ was used as extract method, while they were successfully detected by the ultrasound extract method, including 1–O–galloyl–β–D–glucose to 14–O–galloyl–β–D–glucose. Under the conditions of ultrasonic power of 1 500 W and extraction temperature of 65 ℃, more gallotannin isomers were identified. The MS/MS spectrum showed that gallotannins were mainly decomposed by the loss of glucoside, gallic acid, galloyl, H₂O and carboxyl.

Conclusion In the study, UHPLC–QTOF–MS technology coupled with ultrasonic extraction methods have been proved to determine gallnut tannin comprehensively and efficiently. The identification of gallnut tannin and the analysis of their fragmentation mechanism can provide a reference for research on the chemical composition of other plants rich in tannin.