A comprehensive study of the aerial parts of Lonicera japonica Thunb. based on metabolite profiling coupled with PLS-DA.

Introduction Lonicera japonica Thunb. is an economically important species of honeysuckle belonging to the Caprifoliaceae family. All aerial parts of L. japonica (leaf, flower bud, flower, and caulis) are used as herbal remedies in traditional Chinese medicine. The application of plant metabolomics to the study of L. japonica provides the potential for identifying the phytochemical composition and useful chemical markers of the plant. Objective To develop a strategy integrating metabolic profiling and partial least squares discriminant analysis (PLS-DA) to separate the aerial parts of L. japonica based on the occurrence of chemical markers. Methodology The two-part strategy consisted of (1) ultra-fast liquid chromatography coupled with triple quadrupole-time of flight tandem mass spectrometry (UFLC-triple TOF-MS/MS), (2) PLS-DA, which was applied to distinguish between the different aerial parts and reveal their differential characteristic metabolites. Results A total of 71 metabolites were identified from samples, and eight candidate compounds were identified (lonicerin, kaempferol-3-O-rutinoside, loganin, isochlorogenic acid B, isochlorogenic acid C, secologanic acid, luteoloside, astragalin) as optimal chemical markers based on variable importance in projection (VIP) and p-value. The relative contents of eight candidate compounds were compared based on their peak intensities. Conclusion This study established an efficient strategy for exploring metabolite profiling and defining chemical markers among the different aerial parts of L. japonica, and laid the foundation for elucidating the phytochemical differences in efficacy between Lonicerae Japonicae Flos (LJF) and Lonicerae Japonicae Caulis (LJC). Our findings also indicate that the leaves of L. japonica leaf could be used as an alternative medicinal resource for LJF and provide a reference for comprehensive exploitation and utilisation of L. japonica resources.