Metabolomic studies on Isatis tinctoria - Comparison of different origins, harvesting dates, and the effect of repeated harvesting

Isatis tinctoria (Brassicaceae) is an ancient dye and medicinal plant with potent anti-inflammatory and anti-allergic properties [1]. We investigated metabolic differences by NMR spectroscopy of plants grown under identical conditions on experimental plots at the Agricultural Field Station of Thuringia in Dornburg, Germany. Comparisons were carried out for plants of different geographic origins, different harvesting dates, and between single and repeatedly harvested plants. For the study, plants of six origins were compared, and they were harvested at six time points. In addition, the effect of repeated harvesting was investigated.

Leaf samples were shock-frozen with liquid N₂ immediately after harvest, freeze-dried, and cryomilled prior to extraction. Extracts were prepared by pressurized liquid extraction (PLE) with 70% aqueous methanol. The spectra were analyzed by multivariate data analysis. The score plots produced by principal component analysis (PCA) revealed differences in the metabolic profile between the harvesting dates. The loading plots showed that the spectral region of carbohydrate resonances was responsible for these differences. In contrast, no major differences were seen in the metabolites of different origins. Partial least square discriminant analysis (PLS-DA) revealed no effect of repeated harvesting on the metabolic profiles.

Reference:

[1] Hamburger M., Phytochemistry Reviews, 1, 333 – 344 (2002)