Sasagawa M, Cech NB, Gray D, Elmer G, Wenner CA.

Alkylamide constituents of Echinacea purpurea inhibit interleukin-2 production in mitogen-stimulated Jurkat E6.1 human leukemic T cells.

Bastyr University, 14500 Juanita Dr NE, Kenmore, WA 98028. masas@bastyr.edu

OBJECTIVE: Many different Echinacea formulations with varying levels of proposed active constituents are commercially available. However, the direct effects of Echinacea and its constituents on human T cells that serve a critical role in immune responses are unknown. The purpose of this study was to examine the hypothesis that purportedly bioactive constituents present in ethanolic extracts of Echinacea purpurea exert direct immunomodulatory effects on human T cells. E. purpurea extracts and commercially available standard isolates of Echinacea constituents were assayed to determine their modulatory effects on mitogen-induced IL-2 secretion and cytotoxicity in human lymphocytic, leukemic Jurkat E6.1 T cells.

METHODS: A 96-well plate method allowed simultaneous assay of cytokine secretion and cell viability. IL-2 production levels and cell viability of T cells stimulated submaximally with the mitogen phytohemagglutinin and treated with Echinacea extracts or isolates vs. a 0.5% ethanol vehicle control were determined.

RESULTS: Echinacea extracted in a 95% ethanol menstruum (diluted to 0.5% ethanol on cells) suppressed IL-2 production by 80% at 50 µg/mL. The constituent profiles by HPLC/MS revealed that the inhibitory activity was correlated to the presence of alkylamides and not to caffeic acid derivatives. Alkylamides at the concentration found in a 50 µg/mL extract inhibited IL-2 production by 50%. The 95% ethanol E. purpurea extract-induced decreases observed in IL-2 production and cell viability were both statistically significant at 50 and 100 µg/mL. However, a significant decrease in IL-2 inhibition but not cell viability was observed at lower concentrations. Alkylamide-induced depression of IL-2 production was statistically significant at all concentrations whereas decrease in cell viability was not.

CONCLUSION: E. purpurea extracts with high alkylamide content, as well as purified alkylamide isolates, suppressed the ability of human leukemic T cells to produce IL-2 upon mitogenic stimulation independently of direct, cytotoxic effects.

 

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