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Echinacea (Echinacea spp.)
Date: June 15, 2006
RE: Study Examines Echinacea's Alkamides
Woelkart K, Xu W, Pei Y, Makriyannis A, Picone R, Bauer R. The endocannabinoid system
as a target for alkamides from Echinacea angustifolia
roots. Planta Med.
2005;71:701–705. Echinacea angustifolia
is one of three echinacea species widely used medicinally, the other
two being E. purpurea
and E. pallida
. These plants have a long history of medicinal use by
Native Americans, and are indigenous to the central and southwestern United States.
Traditionally, roots of these plants were used to treat insect and snake bites. Today
echinacea is commonly used to treat upper respiratory disorders and other conditions where
cell-mediated immune stimulation (defending against bacteria and viruses) is desired. Long-
chained fatty acid alkamides found in high concentrations in the aerial parts of all echinacea
species and in the roots of E. angustifolia
and E. purpurea
and are believed to be
responsible at least in part for echinacea's immune-modulating features. Some of the
pharmacokinetic properties (absorption, distribution, and elimination) of echinacea
alkamides were recently defined by Woelkart K et al.1 and others.2
The current in vitro study adds to the growing body of research defining the bioactivity of
echinacea by characterizing the effects of alkamides on two cell receptors (molecules
embedded in cell membranes that translate extracellular signals into intracellular activity),
namely, cannabinoid receptor 1 (CB1) and cannabinoid receptor 2 (CB2). This study used
rat-isolated CB1 and mouse-isolated CB2 receptors. CB1 is most highly concentrated in the
brain, "where it is responsible for the characteristic effects of cannabis, including catalepsy
[rigidity of limbs], depression of motor activity, analgesia and feelings of relaxation and
well being." The CB2 receptor is found in immune cells in the periphery (not in the brain).
These receptors, as well as two other cannabinoid molecules—fatty acid amidohydrolase
(FAAH) and anandamide—"are current targets for the development of novel medications
for pain, immunosuppression, peripheral vascular disease, appetite enhancement or
suppression, and mental illness."
Alkamides were isolated from two-year old E. angustifolia
roots (Heilfpflanzen Sandfort GmbH & Co KG, Olfen, Germany) using supercritical carbon dioxide (CO2) extracted by Finzelberg, Andernach, Germany. This extraction method provided a drug (77:1 extract ratio in 1.30% yield). Alkamides were then isolated from this extract and characterized as: (1) tetradeca-2E
-ene-10,12-diynoic acid isobutylamide, (2) undeca-2E/Z
-diene-8,10-diynoic acid isobutylamides, (3) undeca-2E/Z
-ene-8,10-diynoic acid isobutylamides, (4) dodeca-2E
-diene-8,10-diynoic acid isobutylamide, (5) dodeca-2E
-ene-8,10-diynoic acid isobutylamide, (6) dodeca-2E
-diene-8,10-diynoic acid isobutylamide, (7) dodeca-2E
-triene-8-ynoic acid isobutylamide, (8) dodeca-2E
-tetraenoic acid isobutylamides, (9) pentadeca-2E
-diene-12,14-diynoic acid 2-methylbutylamide, (10) dodeca-2E
-ene-8,10-diynoic acid 2-methylbutylamide, (11) dodeca-2E
-trienoic acid isobutylamide, and (12) dodeca-2E
-dienoic acid isobutylamide. Echinacea alkamides showed a binding affinity (Ki value, which is the concentration of a substance required to inhibit by 50% the activity of a second substance) for CB1 and CB2 receptors. Alkamide 9 showed the greatest binding affinity for CB1, at a concentration of 2.035 (1.6–2.7) µM (micromoles), followed by alkamide 10 (4.116 [2.8–6.1] µM), and alkamide 12 (6.147 [4.8–7.8] µM). On the other hand, alkamide 1 was most selective for CB2, at a concentration of 1.867 (1.0–3.4) µM, followed by alkamide 11 at 4.569 (3.3–6.3) µM, and alkamide 8 at 5.499 (3.7–8.2) µM. In a second experiment, the researchers tested the ability of echinacea alkamides to inhibit the activity of FAAH, which would prolong the activity on CB1 and CB2. FAAH activity was inhibited by 23% by alkamide 1, 14.4% by alkamide 11, and 11.7% by alkamide 12. Interestingly, alkamide 1 showed the highest affinity and selectivity for CB2 and the greatest FAAH inhibition. The characterization of the active alkamides in echinacea root is an important step towards an understanding of echinacea's bioactive compounds and immune system effects. These results need to be confirmed in human cell lines. Future research could standardize the alkamides and test them in human clinical trials. However, the greatest safety and efficacy of echinacea in humans may be when a broadly complex mixture of alkamides and other compounds is administered rather than narrowly fractionated preparations.
1 Woelkart K, Koidl C, Grisold A, et al. Bioavailability and pharmacokinetics of alkamides from the roots of
Echinacea angustifolia in humans. J Clin Pharmacol.
2Dietz B, Heilmann J, Bauer R. Absorption of dodeca-2E,4E,8Z,10E/Z-tetraenoic acid isobutylamides after oral
application of Echinacea purpurea tincture. Planta Med.
Enclosure: Referenced article reprinted with permission from Georg Thieme Verlag.
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