Metabolomics approach reveals discriminatory metabolites associating with the blue pigments from Vaccinium bracteatum thunb. Leaves at different growth stages.

• The metabolic profiling in Vaccinium bracteatum Thunb. leaves were examined. • Dynamic changes of metabolites between different leaf samples were revealed. • Several discriminatory secondary metabolites accounted for the blue pigments. • Several discriminatory free amino acids contributed to the formation of pigment. • A hypothesis of the seasonal differences of blue pigments was presented. Vaccinium bracteatum Thunb. leaf is a valuable source of natural pigment to dye food, hair, and clothing for a thousand of years in China. However, the seasonal differences of blue hue of pigments have not been fully demonstrated. In this research, V. bracteatum Thunb. leaves were collected from eight months for metabolite analysis. The global metabolic profile in leaves was examined to distinguish the differential metabolites and monitor the dynamic changes. This research revealed that several discriminatory secondary metabolites were monotropein derivatives, flavonoid glycosides and chlorogenic acid isomers by LCMS-untargeted approach. The changes of monotropein derivatives and dimers occurred in a season-dependent manner which almost showed higher abundances in spring. Meanwhile, several free amino acids changed dramatically by HPLC-targeted measurement. Particularly, Ala, Glu, and Asp caused a positive impact on blue color. Ser, Arg, and His were negatively correlated with the color. This research provided the first evidence that the seasonal differences of blue pigment are ascribed to the systemic changes of monotropein derivatives and free amino acids in V. bracteatum Thunb. leaves. [ABSTRACT FROM AUTHOR]