Comparison of the Metabolomics of Different Dendrobium Species by UPLC-QTOF-MS

Abstract

Dendrobium Sw. (family Orchidaceae) is a renowned edible and medicinal plant in China. Although widely cultivated and used, less research has been conducted on differential Dendrobium species. In this study, stems from seven distinct Dendrobium species were subjected to UPLC-QTOF-MS/MS analysis. A total of 242 metabolites were annotated, and multivariate statistical analysis was employed to explore the variance in the extracted metabolites across the various groups. The analysis demonstrated that D. nobile displays conspicuous differences from other species of Dendrobium. Specifically, D. nobile stands out from the remaining six taxa of Dendrobium based on 170 distinct metabolites, mainly terpene and flavonoid components, associated with cysteine and methionine metabolism, flavonoid biosynthesis, and galactose metabolism. It is believed that the variations between D. nobile and other Dendrobium species are mainly attributed to three metabolite synthesis pathways. By comparing the chemical composition of seven species of Dendrobium, this study identified the qualitative components of each species. D. nobile was found to differ significantly from other species, with higher levels of terpenoids, flavonoids, and other compounds that are for the cardiovascular field. By comparing the chemical composition of seven species of Dendrobium, these qualitative components have relevance for establishing quality standards for Dendrobium.

Keywords: Dendrobium; UPLC-QTOF-MS/MS; cysteine and methionine metabolism; different species; metabolomics; terpene and flavonoid components.

Figure 1

Representative total ion current (TIC) chromatograms of different species of DD (Dendrobium denneanum Kerr.), DC (D. chrysotoxum Lindl.), DN (D. nobile Lindl.) DF (D. fimbriatum Hook.), DT (D. thyrsiflorum Rchb. f.), DO (D. officinale Kimura. et Migo.), DV (D. devonianum Paxton.) (A) and of DN alone (B) under positive ionization mode.

Figure 2

Proposed schematic of the mass fragmentation pathways of (A) (compound 195, caryoptosidic acid); (B) (compound 10, naringenin chalcone); (C) (compound 33, mangiferin); (D) (compound 63, N-Oxysophocarpine); (E) (compound 197, 6,7-dihydroxy-4-methyl coumarin); and (F) (compound 134, lusianthridin).

Figure 3

Principal component analysis of different species of DD (Dendrobium denneanum Kerr.), DC (D. chrysotoxum Lindl.), DN (D. nobile Lindl.), DF (D. fimbriatum Hook.), DT (D. thyrsiflorum Rchb. f.), DO (D. officinale Kimura. et Migo.), DV (D. devonianum Paxton.) (A); a comparison of verified DN and other species of Dendrobium (B).

Figure 4

A Venn diagram of variance components (A); a heat map of the differential compositions (B).

Figure 5

The outcomes of the metabolic pathway analysis. The main differentiating metabolites were annotated and analyzed about metabolic pathways. Each bubble on the bubble diagram represents a metabolic pathway. Technical term abbreviations are explained upon their first use. The horizontal axis and the size of the bubble indicate the size of the pathway influencing factor in the topology analysis. The greater the scale, the bigger the influencing factor. The vertical position of the bubble shows the p-value of the enrichment analysis.

Figure 6

The key differential metabolites of DN and different species of Dendrobium were mapped to metabolic pathways, and the results of metabolic pathway analysis are shown as KEGG pathway results: (A,D) galactose metabolism; (B,F) flavonoid biosynthesis; (C) cysteine and methionine metabolism; (E) flavone and flavonol biosynthesis.