NMR Metabolomics of Arctium lappa L. , Taraxacum officinale and Melissa officinalis: A Comparison of Spontaneous and Organic Ecotypes

Abstract

Officinal plants are a source of metabolites whose chemical composition depends on pedoclimatic conditions. In this study, the NMR-based approach was applied to investigate the impacts of different altitudes and agronomical practices (Land, Mountain Spontaneous, and Organically Grown Ecotypes, namely LSE, MSE, and OE, respectively) on the metabolite profiles of Burdock root, Dandelion root and aerial part, and Lemon balm aerial part. Sugars, amino acids, organic acids, polyphenols, fatty acids, and other metabolites were identified and quantified in all samples. Some metabolites turned out to be tissue-specific markers. Arginine was found in roots, whereas myo-inositol, galactose, glyceroyldigalactose moiety, pheophytin, and chlorophyll were identified in aerial parts. Caftaric and chicoric acids, 3,5 di-caffeoylquinic acid, and chlorogenic and rosmarinic acids were detected in Dandelion, Burdock and Lemon balm, respectively. The metabolite amount changed significantly according to crop, tissue type, and ecotype. All ecotypes of Burdock had the highest contents of amino acids and the lowest contents of organic acids, whereas an opposite trend was observed in Lemon balm. Dandelion parts contained high levels of carbohydrates, except for the MSE aerial part, which showed the highest content of organic acids. The results provided insights into the chemistry of officinal plants, thus supporting nutraceutical-phytopharmaceutical research.

Keywords: NMR spectroscopy; metabolomics; officinal plants; pedoclimatic conditions.

Figure 1

Molecular structures of polyphenols. To make the assignment discussion easier, the numbering of common portions is the same for the compounds.

Figure 2

Histograms relative to compounds quantified (mg/100 g of dried sample ± SD) in the Bligh–Dyer hydroalcoholic extracts of Burdock in the Land Spontaneous Ecotype (LSE), Mountain Spontaneous Ecotype (MSE), and Organic Ecotype (OE). (A) Sugars, (B) organic acids, (C) amino acids, and (D) other metabolites. One-way ANOVA, followed by Tukey’s multiple comparison test, was applied to underline, among ecotypes, significant differences (p < 0.0001) for each metabolite: (a) vs. MSE; (b) vs. OE.

Figure 3

Histograms relative to compounds quantified (mg/100 g of dried sample ± SD) in the Bligh–Dyer hydroalcoholic extracts of Dandelion in Land Spontaneous Ecotype (LSE), Mountain Spontaneous Ecotype (MSE) and Organic Ecotype (OE), comparing the difference between aerial part (green) and root (brown). (A) Sugars, (B) organic acids, (C) amino acids, and (D) other metabolites. Two-way ANOVA, followed by Tukey’s multiple comparison test, was applied to underline, among ecotypes, significant differences (p < 0.0001) for each metabolite according to the same plant part: (a) vs. MSE; (b) vs. OE.

Figure 4

Histograms relative to compounds quantified (mg/100 g of dried sample ± SD) in the Bligh–Dyer hydroalcoholic extracts of Lemon balm in the Land Spontaneous Ecotype (LSE), Mountain Spontaneous Ecotype (MSE), and Organic Ecotype (OE). (A) Sugars, (B) organic acids, (C) amino acids, and (D) other metabolites. One-way ANOVA, followed by Tukey’s multiple comparison test, was applied to underline, among ecotypes, significant differences (p < 0.0001) for each metabolite: (a) vs. MSE; (b) vs. OE.

Figure 5

PCA model of (A) root parts of Burdock and Dandelion; (B) aerial parts of Lemon balm and Dandelion. The points represent the samples, while the lines represent the directions of growth of the plants’ metabolites. In (A), the Dandelion samples are represented by circles and the Burdock samples are represented by diamonds. The ecotypes are differentiated by colours: red for MSE, blue for LSE, and black for OE. In (B), the Dandelion samples are represented by circles and the Lemon balm samples are represented by diamonds. The ecotypes are differentiated by colours: red for MSE, blue for LSE, and black for OE.