Bioavailability and pharmacokinetics of alkamides from the roots of Echinacea angustifolia in humans

Alkamides are suspected to contribute to the activity of Echinacea preparations. They are mainly derived from undeca- and dodecanoic acid and differ in the degree of unsaturation and the configuration of the double bonds. In total, 6 alkamides have been isolated from the roots of Echinacea angustifolia as major lipophilic constituents and have been investigated regarding their pharmacokinetics. A sensitive and specific method has been developed for the identification and quantification of these alkamides in human plasma using liquid chromatography electrospray ionization ion-trap mass spectrometry. The method was applied to analyze plasma samples obtained from a randomized, open, single-dose, crossover study after oral administration of a 60% ethanolic extract from the roots of E. angustifolia to 11 healthy subjects. The maximum concentration of dodeca-2E,4E,8Z,10E/Z-tetraenoic acid isobutylamides, the main alkamides in the roots of E. angustifolia, appeared already after 30 minutes and was 10.88 ng/mL for the 2.5-mL dose.