The proposed biosynthesis of procyanidins by the comparative chemical analysis of five Camellia species using LC-MS

Abstract

The genus Camellia (C.) contains many species, including C. sinensis, C. assamica, and C. taliensis, C. gymnogyna and C. tachangensis. The polyphenols of C. sinensis and C. assamica are flavan-3-ols monomers and their dimers and trimmers. However, the biosynthesis of procyanidins in Camellia genus remains unclear. In the present study, a comparative chemical analysis of flavan-3-ols, flavan-3-ols glycoside and procyanidins was conducted by high performance liquid chromatography (HPLC) and liquid chromatography diode array detection coupled with triple-quadrupole mass-spectrometry (LC-DAD-QQQ-MS). The results showed that C. tachangensis had a significant higher contents of (-)-epicatechin (EC) and (-)-epigallocatechin (EGC) compared with C. sinensis (p < 0.001). By contrast, higher levels of galloylated catechins were detected in C. sinensis. LC-DAD-MS/MS indicated that the main secondary metabolites of C. tachangensis were non-galloylated catechins, procyanidin dimers and trimers. Furthermore, (-)-epicatechin glucose (EC-glucose) and (-)-epigallocatechin glucose (EGC-glucose) were also abundant in C. tachangensis. A correlation analysis of EC-glucose and procyanidins dimers was conducted in five Camellia species. The levels of EC-glucose were closely related to the procyanidin dimers content. Thus, it was suggested that EC-glucose might be an important substrate for the biosynthesis of procyanidins.