Metabolomic Elucidation of the Effect of Sucrose on the Secondary Metabolite Profiles in Melissa officinalis by Ultraperformance Liquid Chromatography–Mass Spectrometry

Sucrose induces flavonoid accumulation in plants as a defense mechanism against various stresses. However, the relationship between the biosynthesis of flavonoids as secondary metabolites and sucrose levels remains unknown. To understand the change in flavonoid biosynthesis by sucrose, we conducted secondary metabolite profiling in Melissa officinalis treated with different levels of sucrose using ultraperformance liquid chromatography/quadrupole time-of-flight mass spectrometry. The partial least squares-discriminant and hierarchical clustering analyses showed significant differences in secondary metabolite profiles in M. officinalis at 50, 150, and 300 mM sucrose levels. The levels of 3 flavonoids such as quercetin 3-O-β-d-glucosyl-(1→2)-β-d-glucoside, 6-methoxyaromadendrin 3-O-acetate, and 3-hydroxycoumarin and 19 flavonoids including 6-methoxyaromadendrin 3-O-acetate, aureusidin, iridin, flavonol 3-O-(6-O-malonyl-β-d-glucoside) quercetin 3-O-glucoside, and rutin increased at 150 and 300 mM sucrose, respectively, compared to 50 mM sucrose, indicating that the flavonoids were accumulated in M. officinalis by a higher concentration of sucrose. This is the first investigation of the change in individual flavonoids as secondary metabolites in M. officinalis by varying sucrose levels, and the results demonstrate that the sucrose causes the accumulation of certain flavonoids as a defense mechanism against osmotic stress.