Echinacea fruit: phytochemical localization and germination in four species of Echinacea

Abstract

Plants of the genus Echinacea have received extensive research attention, yet relatively little is known about the fruit (cypselae) of this economically important genus. The goal of this study was to investigate and compare the cypselae of four species of Echinacea: E. purpurea (L.) Moench, E. angustifolia DC., E. pallida (Nutt.) Nutt., and E. paradoxa (Norton) Britton, with respect to chemistry and germination. The phytochemical content of various fruit fractions was analyzed by high performance liquid chromatography with diode-array detection, identifying several alkylamides and caffeic-acid derivatives of medicinal value in all of the tissues. Alkylamides were most concentrated in the perianth and glands, whereas phenolics were generally enriched within the seed. Germination studies of intact cypselae and de-coated seeds demonstrate that the influence of cypsela coatings on germination depends on the growth environment. Removal of the perianth and pericarp resulted in decreased germination in soil, but significantly improved the germination of seeds of all species when sown in a sterile agar medium. In contrast, a higher percentage of intact cypselae of E. purpurea, E. angustifolia, and E. pallida germinated in soil than in sterile agar. These results suggest an ecophysiological role for phytochemicals in seed germination and will inform the cultivation and breeding of less common Echinacea species as well as the development of new products from currently unused plant material.