Distribution of Metabolites in Root Barks of Seven Tree Peony Cultivars for Quality Assessment Using NMR-based Metabolomics

Objective To determine the distribution of metabolites in the root barks of different tree peony cultivars for quality assessment. Methods Seven tree peony phenotypic cultivars with different colors were systematically analyzed using NMR-based metabolomics. Results A total of 16 metabolites from their methanol extracts were simultaneously identified and quantified, including one primary metabolite （sucrose） and 15 secondary ones （acetophenones, phenolics, monoterpene glycosides, flavonoids, and unsaturated fatty acids）. The quantitative data indicated that sucrose （90-180 mg/g） and acetophenones （15-100 mg/g）, and non-phenolics, monoterpene glycosides, flavonoids, and unsaturated fatty acids （2-15 mg/g） were the major metabolites in these tree peony cultivars. The significantly increasing levels of paeonoside with bioactivity were observed in ＂Xiangyu＂, ＂Wujinyaohui＂, ＂Roufurong＂, ＂Yaohuang＂, ＂Zhaofen＂, ＂Doulu＂, and ＂Yingrihong＂ in order. Opposite trends in the levels of paeonoside and paeonol were observed in ＂Xiangyu＂ and ＂Yingrihong＂, suggesting that the changes of the secondary metabolites in plants were influenced by primary metabolites, such as sucrose/glucose, and the different physiological processes occurred in different tree peony cultivars. Conclusion ＂Yingrihong＂ with red flower has the highest medicine quality whereas ＂Xiangyu＂ with white flower has the worst one based on the content of paeonoside.