Metabolomics Analysis on Different Parts of Ligustrum lucidum Ait. Based on UPLC–Q-TOF-MS

BACKGROUND: Ligustri Lucidi Fructus (LLF), the dried fruit of Ligustrum lucidum Ait. (LLA), is a traditional Chinese medicine used for nourishing the liver and the kidney. OBJECTIVE: To chemically characterize and compare medicinal and non-medicinal plant parts of LLA to potentially improve biomass utilization. METHOD: The metabolite profiles of three different plant parts were evaluated by ultra-performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-QTOF-MS/MS). PCA (principal components analysis) and PLS-DA (partial least-squares discriminant analysis) were used to compare the chemical composition of the leaf, stem, and fruit of LLA. Differential metabolites were analyzed via the Pathway Analysis module of MetaboAnalyst 5.0 for pathway enrichment. RESULTS: A total of 37 compounds were identified from three different plant parts by UPLC-QTOF-MS/MS combined with UNIFI v1.8.1 software. Significant metabolic differences were observed between the leaf, stem, and fruit of LLA using PCA and PLS-DA. Eleven compounds were identified as markers. The content of loganate, secologanoside, nuzhenal C, luteolin, iso-oleonuezhenide, and dammarenediol-II was very much higher in the fruit than in the leaf and stem. The content of oleanolic acid was higher in the fruit and stem than in the leaf. Metabolic pathway analysis revealed that triterpenoids (dammarenediol-II, oleanolic acid, and β-amyrin) exhibited significantly higher abundance in the fruit and stem than in the leaf. CONCLUSION: The stem of LLA may be processed as a source of oleanolic acid in the future. This study laid the foundation for the rational utilization of non-medicinal LLA resources.