Influence of Nitrogen and pH On Constituent Levels and Plant Growth of Greenhouse Grown Echinacea Purpurea

Echinacea purpurea is one of the most popular medicinal herbs with annual sales in the United States of over $120 million.  Although commonly used for the treatment of colds and flu, results from numerous studies on its effectiveness have been inconclusive.  Consistency of raw material used to make products and positive identification of the bioactive constituents are two issues that must be addressed before reliably effective E. purpurea preparations can be developed.  A study was conducted to determine whether levels of several chemical constituents in E. purpurea can be manipulated by changing soil pH and nitrogen.  Plants were grown in soilless media in pots in the greenhouse.  The experimental design was a RCB factorial with three initial soil pH levels (5.85, 6.35, and 7.0) and three nitrogen rates (50, 100, and 200 mg N/kg media).  There were nine plants in each treatment.   Two plants were harvested from each treatment at three different stages of growth (emerging, flowering, and post-bloom). Extra plants were produced to ensure that two plants at the same stage of growth could be harvested on the same day.  Roots were washed and dried at 38 °C under positive air flow.  The dried roots were pulverized, extracted in 75% ethanol, and analyzed for active constituents using reversed phase HPLC coupled with electrospray ionization mass spectrometry. Plants responded to increasing nitrogen with more vigorous growth, greater numbers of blooms, and higher total biomass. Soil pH, however, had little effect.  Laboratory analysis revealed that none of the factors affected concentrations of one of the major alkylamides of interest, dodeca-2E,4E,8Z,10E-tetraenoic acid isobutylamide.  Interestingly, the outcomes from parallel studies with isolated alkylamides and ethanolic alkylamide containing extracts suggested that this compound may play an important role in the anti-inflammatory activity of Echinacea.  Therefore, it appears that it is possible to manipulate growing conditions to boost production of Echinacea without compromising production of one of its anti-inflammatory constituents (dodeca-2E,4E,8Z,10E-tetraenoic acid isobutylamide).  Based on these findings, Echinacea growers may want to increase nitrogen fertilization to increase total plant yields.