The Role of Alkamides as an Active Principle of Echinacea

Abstract

Alkamides are the major lipophilic constituents of Echinacea preparations, which are widely used in some European countries and in North America for common colds. In earlier investigations they have been shown to possess stimulatory effects on phagocytosis. Recent experiments have demonstrated that alkamides are detectable in human blood in relevant concentrations after oral administration of Echinacea preparations. Alkamides show structural similarity with anandamide, an endogenous ligand of cannabinoid receptors. Consequently, it was found that alkamides bind significantly to CB₂ receptors, which is now considered as a possible molecular mode of action of Echinacea alkamides as immunomodulatory agents. It was also demonstrated recently in several studies that alkamide-containing Echinacea preparations trigger effects on the pro-inflammatory cytokines. They were therefore suggested as a new class of cannabinomimetics. However, the therapeutic relevance of these findings is still not clear as clinical studies on the common cold show contradictory results. Among the many pharmacological properties reported, investigations concerning herb-drug interactions have been neglected for a long time. Latest research concludes that prolonged use of Echinacea poses a minimal risk for co-medications metabolized by the P450 enzymes.

Key words

Alkamides - Echinacea purpurea - Echinacea angustifolia - Asteraceae - immunomodulation - pharmacokinetics - cannabinoid receptor binding - herb-drug interactions

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