Metabolite Profiling and Comparative Analysis of Secondary Metabolites in Chinese Cabbage, Radish, and Hybrid xBrassicoraphanus.

Abstract

We profiled and quantified primary and secondary metabolites in the leaves and roots of xBrassicoraphanus (Baemuchae), Brassica campestris ssp. pekinensis (Chinese cabbage), and Raphanus sativus (radish). We obtained 72 metabolites from leaves and 68 metabolites from both leaves and roots of xBrassicoraphanus, Chinese cabbage, and radish. The metabolic profiles in this study revealed intermediate-level production of most metabolites from different parts of Baemuchae compared with that from different parts of Chinese cabbage and radishes. This was supported by the results of principal component analyses for the detected metabolites, which indicated that the Baemuchae group was located between the Chinese cabbage and radish groups. In particular, several amino acids (phenylalanine, tryptophan, and methionine) played the main role in phenylpropanoid and glucosinolate biosynthesis and were positively correlated with phenolic compounds, indolic glucosinolates, and aliphatic glucosinolates, respectively, in different parts. Furthermore, analysis of different species revealed the presence of 10 different glucosinolates, 10 phenolics, and 7 carotenoids, and their levels varied in the roots and leaves of the studied species. Among the leaves of the three species, Chinese cabbage had the highest total glucosinolate level, which was 3.14 times higher than the lowest level observed in radish. Baemuchae had the highest total phenolic compound level, which was 2.87 times higher than the lowest level found in Chinese cabbage, and radish had the highest carotenoid level, which was 12.41 times higher than the lowest one observed in Chinese cabbage. In the roots of Baemuchae, Chinese cabbage, and radish, glucosinolate levels did not vary significantly. Chinese cabbage contained the highest total phenolic compound level, which was 2.38 times higher than the lowest level found in radish, and the highest total carotenoid level, which was 2.49 times higher than the lowest level observed in Baemuchae. This metabolomic study provided chemical composition information that can be applied to future breeding strategies and comprehensively described the relationship among metabolites detected in the three plant species.