Identification and characterization of phenolamides in tea (Camellia sinensis) flowers using ultra-high-performance liquid chromatography/Q-Exactive orbitrap mass spectrometry.

Abstract

Phenolamides (PAs) are important secondary metabolites present in plants with multiple bioactivities. This study aims to comprehensively identify and characterize PAs in tea (Camellia sinensis) flowers using ultra-high-performance liquid chromatography/Q-Exactive orbitrap mass spectrometry based on a lab-developed in-silico accurate-mass database. The PAs found in tea flowers were conjugates of Z/E-hydroxycinnamic acids (p-coumaric, caffeic and ferulic acids) with polyamines (putrescine, spermidine and agmatine). The positional and Z/E isomers were distinguished through characteristic MS2 fragmentation rules and chromatographic retention behavior summarized from some synthetic PAs. 21 types of PAs consisting of over 80 isomers were identified, and the majority of them were found in tea flowers for the first time. Among 12 tea flower varieties studied, they all possessed tris-(p-coumaroyl)-spermidine with the highest relative content, and C. sinensis 'Huangjinya' had the highest total relative contents of PAs. This study shows the richness and structural diversity of PAs in tea flowers.