Selected secondary metabolites in Echium vulgare L. populations from nonmetalliferous and metalliferous areas

Abstract

The aim of this study was to evaluate the effect of severe environmental conditions prevailing on metalliferous waste heaps and heavy metal-contaminated growth substrates on accumulation of selected secondary metabolites, antioxidant capacity, and heavy metal concentration in two metallicolous (MC, MZ) and one nonmetallicolous (NM) populations of Echium vulgare L. The shoots and the roots of the three studied populations were collected from their natural habitats. Additionally, the plants were cultivated on different growth substrates, i.e. a contaminated substrate obtained from the areas of growth of the MZ and MC populations and an uncontaminated one from the NM population site. Several compounds, i.e. allantoin, rutin, rosmarinic acid, chlorogenic acid, and 4-hydroxybenzoic acid were identified in the shoots. Moreover, rosmarinic acid, allantoin, and shikonin were measured in the roots. The adverse environmental conditions contributed to a ca. 10- and 4-fold increase in the concentration of allantoin in the roots and shoots, respectively, as well as a ca. 4-fold and ca. 3-fold increase in the level of 4-hydroxybenzoic acid and shikonin, respectively, in comparison with the plants from the uncontaminated site. Similarly, a great impact of the contaminated substrate on the compounds was demonstrated in the soil experiment. Regardless of the populations, even ca. 20-fold higher levels of allantoin and shikonin were observed in plants grown on the MC and MZ substrates. In contrast, the chlorogenic acid concentration was lower in plants collected from the metalliferous areas and in all populations cultivated on the contaminated substrates in comparison with plants from the uncontaminated soil. Unambiguous results were obtained in the case of rutin, i.e. decreased accumulation in both metallicolous populations from the natural environment and increased accumulation in plants grown on the contaminated substrates. The high concentrations of heavy metals in the substrates contributed to high HM concentrations in plant tissues. However, some differences were observed between the metallicolous and nonmetallicolous populations - the accumulation of metals was lower in the shoots and higher in the roots of the NM population, compared with the MZ and MC populations.

Keywords: Allantoin; Antioxidant capacity; Boraginaceae; Echium vulgare; Flavonoids; Heavy metals; Metallicolous population; Phenolic compounds; Shikonin.