CYP3A4 inhibitory compounds from Echinacea extract (Echinaforce®)

Echinacea is one of the best selling herbal medicinal products, with an established role in the prevention and treatment of the common cold. Thus, information on its potential interactions with conventional medicines is of clinical significance[1]. Previously, we showed that Echinacea preparations weakly inhibit various CYP isoforms (including CYP3A4) and that the class of alkylamides are the major inhibitory species [2].

Previously we used a metabolomic approach (NMR fingerprinting) to investigate the CYP3A4 inhibitory components. Here we extended this work by using Liquid chromatography-mass spectrometry (LC-MS) to identify the major components of the inhibitory fractions and further characterise them with accurate mass and tandem MS. In addition the alkylamides of six commercially available Echinacea extracts were detected against a working standard using reverse phase high performance liquid chromatography (HPLC).

We have identified alkylamide 1 (dodeca-2E,4E,8Z,10E/Z-tetranoic acid, M-H⁺-248), and a new compound 2 (M-H⁺-282) with putative molecular formula C₁₈H₃₆NO⁺, in the inhibitory fractions. We suggest that this compound could be 1-amino-octadeca-3,17-dien-1-ol. HPLC analysis revealed that alkylamides 1 and 3 (undeca-2E,4E/Z-diene-8,10-diyonic acid isobutylamide), were good predictors of CYP3A4 inhibition. Of all the alkylamides tested, 1 (CYP3A4 IC₅₀: 7.71µM) is the most abundant in all extracts while 3 (IC₅₀: 0.46µM) is the most potent. Additionally the acetylene tetradeca-8Z-ene-11,13-diyn-2-one, which is used as an industrial marker for Echinacea species discrimination, was unexpectedly found in the E. purpurea extracts. Our results confirm the role of alkylamides in contributing the weak inhibitory effects observed and suggest that alkylamides are useful as industrial markers.

Acknowledgements: Bioforce for funding this project.

References: 1. Heinrich, M. et al. (2008) Planta Med. E pub. DOI: 10.1055/s-2008–1034292. 2. Modarai, M. et al. (2007) Journal of Pharmacy and Pharmacology 59: 567–573.