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Indications supported by clinical trials
The
three medicinal species of Echinacea contain multiple pharmacologically-active
constituents in their flowerheads, leaves, and roots. The chief constituents
include water-soluble polysaccharides (inulin in E. angustifolia with arabinogalactans and arabinoxylan
in the other two species), caffeic and ferulic acid derivatives (e.g.
cichoric acid, echinoside), glycoproteins, and fat-soluble alkylamides
along with volatile oils, flavanoids, and trace amounts of 1,2 saturated
pyrrolizidine alkaloids (not the unsaturated alkaloids implicated in hepatotoxicity).3-6
The constituents vary between species, by part of the plant examined (i.e.,
above ground plant vs. root), and by growing conditions, time of harvest,
etc.7 All three species have alkylamides,
primarily unsaturated isobutylamides, though the concentration is highest
in E. angustifolia roots.8
All three species also produce polysaccharides, such as echinacin B, in
their leaves and flowers, but the concentration is greatest in E. purpurea. E. angustifolia root contains higher concentrations
of caffeic acid esters (0.6-2.1%), including echinoside9 and cynarin.10 In a comparison study of the three
species, Sloley found that cichoric acid and verbascoside were prominant
in E. purpurea root though cynarin and dodeca-2E,4E,8Z,10Z/E-tetraenoic
acid isobutylamides were present in E. angustifolia root extracts. E. pallida root extracts contained predominantly
echinacoside and 6-O-caffeoylechinacoside.11
The
mechanism of action of the Echinacea constituents is not clearly understood,
though researchers have advanced several theories. In vitro and animal studies suggest that
Echinacea enhances nonspecific immunity.12 Its activities include: increase in natural-killer cells
and monocytes,12 inhibition of tissue and bacterial
hyaluronidase,4
increase in granulocyte phagocytosis,13 increase in WBC mobility,4 increase in release of tumor necrosis factor (TNF) and interferon,14 stimulation of fibroblasts,4 stimulation of macrophage activity,8 increase in cytokine production,15 stimulation of antibody production,5 antioxidant activity,11 and inhibition of tumor cells.16 Other researchers contend that Echinacea
serves as an immunomodulator with both stimulatory and anti-inflammatory
activity.8,17-20
Toxicity
studies are underway at the National Toxicology Program and at Gaia Herbal
Research Foundation. Previous results revealed no significant toxicity
from oral administration of E. purpurea juice (LD50 >15,000 mg/kg) with sedation and
dyspnea at very high doses intravenously ( LD50 >5,000 mg/kg
in rats).21 Echinacin, a German pharmaceutical,
did not cause mutations or chromosomal abnormalities.22
Herbal properties: Alterative, analgesic, antiedemic, antiexudative,
anti-inflammatory, antispasmodic, antiseptic, antiviral, fungicidal, immunostimulant,
protisticidal, sialogogue, trichomonicidal, vasodilator, vulnerary.23
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Preparation and dosage: Many preparations of Echinacea are
available commercially in a variety of forms, including tea bags, capsules,
alcoholic tinctures and fluid extracts, and non-alcoholic liquid formulations
that are stabilized in glycerin or concentrated in a liquid filled capsule.
The products contain various species and plant parts and cannot be considered
as equivalent. Clinical trials have employed different formulations as
well. At this time, the gaps in scientific knowledge regarding the optimal
concentrations of the constituents and their bioavailability in different
forms make a definitive recommendation of a specific product impossible.
Some scientists recommend the use of a liquid form or buccal tablet of
Echinacea, because of its possible capacity to stimulate tonsillar lymphoid
tissue.26
Regardless
of the form, most herbalists suggest very frequent dosing of Echinacea
at the time the first symptoms appear in the case of acute infections,
i.e., every 2-3 hours while awake6,27, and followed by tapering
dosage schedules as the symptoms abate. They usually recommend using one
dropperful (40 drops) of a 1:3-1:5 tincture in 30-45% EtOH containing
E. purpurea herb and root, with perhaps the addition of E. angustifolia root. (Tieraona Low Dog, MD, Chair of the USP Dietary Supplement
Information Committee, notes that Echinacea is often underdosed, which
greatly compromises its effectiveness.38) The tea is prepared by steeping one tea bag in a cup of
water for 15 minutes or simmering 1 tsp of root for 15 minutes and drinking
one cup every 2-3 hours.
The
German Commission E recommends the following for chronic conditions:
-
E.
purpurea fresh pressed juice, total of 6-9 ml/ day
-
(3
cc BID-TID corresponding to 300 mg BID-TID)
-
E.
angustifolia root, total of 2-6 ml of 1:2 fluid extract or 5-15
ml of the 1:5 tincture
-
E.
purpurea root, 1:2 fluid extract, 3-9 ml/day or 7.5-22.5 ml of
the 1:5 tincture
Dosage
may be increased for acute infections.
Patients
may note a tingling, numbing sensation on the tongue when taking the tincture,
due to the isobutylamides. The glycerin preparations are not associated
with tingling.
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