Effect of ecological factors on the accumulation of phenolic compounds in Iris species from Latvia, Lithuania and Ukraine.

Abstract

It is important to conduct studies on the influence of environmental factors on the accumulation of secondary metabolites in plants, as well as the cultivation of plants and harvesting of their raw material. In this study, we examined the influence of habitat types, soil composition, climatic factors and altitude on the content of phenolic compounds in Iris species from different populations in Latvia, Lithuania and Ukraine. According to high-performance liquid chromatography (HPLC) analysis, 25 compounds (flavonoids, isoflavonoids, isoflavonoid glucosides, xanthones, phenolcarboxylic acids) were identified in the methanol extracts of 16 samples of Iris rhizomes. The quantitative data were further analysed by principal component analysis (PCA) to reveal the impact of environmental factors on the accumulation of compounds in plants. Iris pseudacorus from Latvia and Lithuania had a more diverse composition of phenolic compounds than samples from Ukraine. Sampled plants of the Iris subg. Iris had a higher content of the analysed compounds than those of Iris subg. Limniris. PCA results showed that the levels of phenolic compounds in Iris rhizomes were influenced by the content of soil nutrients. The phosphorus and potassium content had a significant impact on the levels of phenolic compounds, whereas the impact of nitrogen content was not significant. Meteorological factors had a small impact; however, sunshine duration had a significant positive effect and the amount of precipitation had a significant negative impact. The results of this study suggest that rhizomes of Iris species may be an important source of pharmacologically active compounds such as flavonoids, isoflavonoids and xanthones. Studies on the effect of environmental factors on the production and accumulation of secondary metabolites in Iris species are important because they contribute to knowledge of quantitative parameters of secondary metabolites in medicinal plants and could be employed for the cultivation and harvesting of raw material for medicinal purposes.