Accumulation of bioactive substances and chemical elements in Echinacea purpurea (L.) Moench medicinal herb as influenced by soil application of copper, an essential microelement

Copper, an essential element in human metabolism, is a trace element for plants and animals. It plays a significant role in physiological processes (i.e. in photosynthesis, respiration, carbohydrate and protein metabolism), increases productivity, improves plant quality characteristics and increases resistance to adverse factors. A particular concern is the need to apply copper fertilizers in the biogeochemical provinces with Cu deficit in the soil. Echinacea purpurea (L.) Moench is one of the best-selling plant-based medicines in many developed countries around the world. It has been widely used in medicine and veterinary medicine for immunocorrection. However, publications on the effect of trace elements on the yield and content of biologically active substances in the medicinal raw materials of the E. purpurea are very few. Our study presents the results confirming the role of copper fertilizers in increasing the content of biologically active substances in the medicinal raw materials of E. purpurea , as well as in its enrichment with certain trace elements. The work aimed to assess the influence of essential microelement (Cu) on the accumulation of certain biologically active substances (tanning substances, carotene, vitamin C) and chemical elements (zinc and copper) in the medicinal raw material of E. purpurea variety Znakhar. The plot tests were run in the conditions of the southern forest-steppe of Western Siberia (an experimental field of Omsk Stolypin State Agrarian University, Omsk, May-September 2016-2018). The experiment design was as follows: absolute control (without fertilizers), N125 (N-based fertilizer), N125 + 0.25MAC Cu (the maximum allowed concentration) (2.3 kg a.m./ha), N125 + 0.5MAC Cu (4.7 kg a.m./ha), N125 + 0.75MAC Cu (7.0 kg a.m./ha), N125 + 1MAC Cu (9.4 kg a.m./ha). The soil of the test site was meadow chernozem, low-power, low humus, medium loamy with a 5.2 % humus content, 10.0 mg/kg nitrate nitrogen, 394 mg/kg mobile phosphorus, 749 mg/kg exchange potassium; pH 6.5-6.8. The mobile copper level in the soil was 0.3 mg/kg. The experiment was arranged in four replicates, plots were systematically located in several tiers, with a plot size of 10 m2. Copper acetate (CH3COO)2Cu (32 %) was used as Cu fertilizer, ammonium nitrate (34.4 %) was an N-based fertilizer. The crop was planted at the end of May 2016, 24 plants per plot, with 70×60 cm spacing. Fertilizers were manually incorporated into the soil to a 10-15 cm depth before planting (at tilling), and uniformly distributed throughout the entire plot area. Plants were collected in September, during E. purpurea mass flowering phase. Tannings, carotene, and ascorbic acid were quantified in the medicinal raw material of E. purpurea . The concentration of trace elements (copper, zinc) in powdered herb samples was determined by atomic absorption spectroscopy. We have found out that a single application of copper fertilizers contributed to accumulation of tanning substances, ascorbic acid and carotene in the herb raw material. On average, over three years of our research, the level of bioactive substances in the raw material (grass) increased reliably (p 3COO)2Cu contributes to an improved medicinal value of E. purpurea . The copper fertilizer dosages correlated tightly with the level of mobile zinc and copper in medicinal raw materials ( r = 0.98, p 125 increased the content of mobile copper and zinc in E. purpurea raw material by 0.23 and 1.15 mg/kg, respectively. These values are b coefficients that evaluate the effects of copper fertilizers and, together with the regression equations we obtained, allow practitioners to draw up protocols for applying micronutrient fertilizers in meadow chernozem soils at an early stage of E. purpurea plant development in specific growing conditions.