Correlation between the dynamic accumulation of the main effective components and their associated regulatory enzyme activities at different growth stages in Lonicera japonica Thunb

Abstract

Flos Lonicerae Japonicae (FLJ), the dried flower buds of Lonicera japonica Thunb (Caprifoliaceae), is of high medicinal value in traditional Chinese medicine. Chlorogenic acid (CGA) and luteoloside are used as standard compounds to evaluate the chemical quality of FLJ. The relationship between the activities of the regulatory enzymes associated with CGA and luteoloside biosynthesis during different growth stages remains unclear. In this study, we systematically examined the dynamic accumulation of both compounds at six growth stages in L. japonica [(young alabastrum (S1), green alabastrum (S2), slightly white alabastrum (S3), whole white alabastrum (S4), silvery flower (S5), and golden flower (S6)] using an HPLC-DAD-base method. Additionally, physiological and biochemical methods were used to assay the regulatory enzyme activities. The following results indicated that: (1) The accumulation of both CGA and luteoloside first increased and then decreased throughout the growth of L. japonica. The highest content of CGA was observed in S3 (44.88μg/mg), followed by S5 (41.19μg/mg). The amount of luteoloside was relatively higher in S3 (1.41μg/mg) and S4 (1.34μg/mg) compared with that at other growth stages. (2) The activity of hydroxycinnamoyl-CoA quinate transferase (HQT) and chalcone isomerase (CHI) exhibited a positive correlation with the accumulation of CGA and luteoloside at different growth stages in L. japonica, respectively. In addition, the accumulation of CGA and luteoloside at different growth stages in L. japonica was also correlated with variation in the initial activities of several other regulatory enzymes in the phenylalanine metabolic pathway, including phenylalanine ammonia-lyase (PAL), cinnamate 4-hydroxylase (C4H) and 4-coumarate CoA ligase (4CL). (3) Based on the relative higher yields of both CGA and luteoloside in S3 and S4, these stages are thus recommended as the best harvesting time for FLJ.