Clinical Trials

MediHerb invests significantly into the future of herbal medicine and our profession by funding clinical trials. MediHerb has a reputation for its extensive depth of scientific knowledge and is often approached by research groups to collaborate on projects investigating herbal therapies. MediHerb assesses each of these requests closely and applies stringent criteria to assess viability. The trial must fit with MediHerb’s philosophy of superior quality, innovative, and holistic herbal solutions, and must be conducted at a reputable research establishment. MediHerb does not fund or involve itself with research that utilises animals as human models.

 

The MediHerb Echinacea Research Story

Introduction

Echinacea Purpurea (1)The most well-known herbal support for the immune system is Echinacea. But many patients and health care professionals are confused as to the best way to use this herb. There are many Echinacea products available which differ according to plant species (E. angustifolia, E. purpurea or E. pallida or combinations of these), plant part (root, leaves or seeds or combination of these), quality markers (alkylamides, polysaccharides or caffeic acid conjugates such as cichoric acid) and dosage.

 

Underlying this diversity of preparations is a lack of consensus over what phytochemicals are responsible for Echinacea's immune activity, and only a rudimentary understanding of the exact mode of action of this herb on immune function.

 

However, recent research, in which the MediHerb scientific team has played a key role, has provided some answers to these key questions. In particular the alkylamides, the unique and characteristic phytochemicals found mostly in the roots of E. angustifolia and E. purpurea have been shown to be the best choice as markers of immune activity.

 

Historical Context

Before discussing the exciting new research developments for Echinacea, its use as an immune herb needs to be understood in its historical context. Information about the value of Echinacea first came from the Native American tribes. Their use of Echinacea was then adopted by the Eclectics, a group of practitioners who were prominent around the late 19th and early 20th Centuries in the United States. By 1921 Echinacea (specifically the root of E. angustifolia) was by far the most popular treatment prescribed by the Eclectics.1 The Eclectics used Echinacea for about 50 years and accumulated extensive clinical experience in its use. The best sources of such uses are King's American Dispensatory2 and Ellingwood.3


What  is also important to note is that Echinacea's reputation as an immune support herb came from the solid traditional data generated by the Eclectics on only one form of Echinacea: a fluid extract of the dried root of E. angustifolia extracted in a high percentage of alcohol. We can call this a "traditional Echinacea extract" and, because it was extracted in a high percentage of alcohol, the term "lipophilic extract" (fat-loving) is also relevant. In particular, the Eclectics defined good quality Echinacea root "as imparting a persistent tingling sensation" which is clear reference to alkylamide levels as a quality indicator.2

 

In Europe during the 1930s the German herbalist Madaus used E. purpurea as he was more successful at growing this species. His interest in homoeopathy led him to use the stabilised juice of fresh E. purpurea tops. This remains the most popular form of Echinacea in Germany today (and contains very low levels of alkylamides). We can call this style of product a "hydrophilic extract" (water-loving) of Echinacea.

 

Naturally German scientists were interested to investigate how these new hydrophilic extracts of Echinacea might work in the body and undertook a search for active components. Polysaccharides possessing immunological activity were isolated from the aerial parts of E. purpurea.4 Some clinicians and scientists then mistakenly applied this research to the very different lipophilic or traditional Echinacea preparations, and came to the conclusion that they were inferior because of their low or absent content of polysaccharides. (The low levels of polysaccharides in traditional Echinacea extracts are due to the low starting levels in the root and the fact that high levels of alcohol do not effectively extract these water-loving molecules.)

 

However, many herbal clinicians remained unconvinced. A key aspect of modern phytotherapy is a respect for traditionally-generated knowledge and this suggested that a lipophilic extract of E. angustifolia root was the preferred form. Some felt that the concept of polysaccharides failed to explain what was unique about Echinacea and expressed concerns about the low oral bioavailability of these large, polar compounds.5 So what was clearly needed was a different understanding of Echinacea, especially of the phytochemicals important for the activity of traditional Echinaea products and their mode of action on the immune system. 

 

What is Active Must First be Absorbed

It can be concluded from both traditional use and clinical studies that Echinacea acts on the immune system at various sites in the body. Hence for Echinacea to exert this influence, the active phytochemicals must be absorbed in significant quantities in the bloodstream. Accordingly MediHerb undertook both test tube (in vitro) and clinical (pharmacokinetic) research to understand which of the key phytochemicals in Echinacea were absorbed.

 

The Caco-2 Intestinal Absorption Model

A particular strain of human colon cells (Caco-2) can be grown in a test tube to form a tight layer of single cells (a monolayer). This can serve as a model of absorption by the human digestive tract. The test components are placed on one side of the monolayer and after a period of time anything that has been transported across to the other side of the monolayer is sampled and measured. When the MediHerb scientists carried out this research using the Echinacea Premium extract (made from the roots of E. angustifolia and E. purpurea) they found that:

 

  • All the alkylamides were transported across the Caco-2 monolayer
  • The caffeic acid derivates were not transported

 

Results from this model indicated that only the alkylamides in Echinacea Premium are likely to be absorbed (and hence bioavailable to the immune system)

 

This Caco-2 work by MediHerb and collaborators is published as: Matthias et al in the Journal of Clinical Pharmacy and Therapeutics 2004; 29: 7-13. Another paper entitled "Bioavailability of Echinacea constituents: Caco-2 monolayers and pharmacokinetics of the alkylamides and caffeic acid conjugates" was published as: Matthias et al in Molecules 2005; 10: 1242-1251.

 

Absorption in Human Volunteers

These results from the Caco-2 model were confirmed in a human pharmacokinetic study. Basically, volunteers took four tablets of Echinacea Premium with a meal and the levels of any detectable Echinacea phytochemicals were measured in their blood. It was only alkylamides that could be detected in the blood after taking Echinacea Premium. There were no caffeic acid conjugates found and no degradation products of these or the alkylamides. This work was published in August 2005 by MediHerb and collaborators as: Matthias A et al in Life Sciences 2005; 77: 2018-2029.

 

The Importance of Liver Metabolism

Only alkylamides were found in human plasma after ingestion of Echinacea Premium tablets, but the levels were quite variable and first pass liver metabolism was suspected as influencing this observation. (First pass metabolism is the rapid degradation by the liver as the products from digestion first pass through the liver on their way to the general circulation). The alkylamides mainly found in E. purpurea were found to be rapidly degraded by human liver microsomes. In contrast the alkylamides mainly found in E. angustifolia were much more slowly degraded. Interestingly, it was discovered that the latter type of alkylamide actually slowed down the rate of degradation of the former type of alkylamide. This protective effect of the E. angustifolia alkylamide is a highly novel finding and it was deduced that the presence of only relatively small proportions of this compound will result in a product with enhanced bioavailability. This is a strong justification for the combination if E. angustifolia root with E. purpurea root, as in Echinacea Premium. A patent has been applied for to protect this very important finding. This work has been published as: Matthias A et al in Chemico-Biological Interactions 2005; 155: 62-70.

 

Echinacea Premium: Liquid versus Tablets

One question that is often asked is whether herbs work better as liquids or tablets.

 

MediHerb tablets are likely to work just as well as liquids because they are made using extracts (not the powdered herb) and are formulated to pharmaceutical standards to ensure rapid disintegration. This was verified in a clinical study which compared equivalent doses of Echinacea Premium in liquid or in tablet form.

 

The total amount of alkylamides absorbed into the bloodstream was essentially the same for both products

 

This work has been published as: Matthias A et al Comparison of Echinacea alkylamide pharmacokinetics between liquid and tablet preparations. Phytomedicine 2007; 14(9): 587-590. To our knowledge it is the first study of this kind (comparing the bioavailability of equivalent doses of a herbal liquid against a tablet) ever undertaken.

 

What is Absorbed Must be Active

The research undertaken by the MediHerb team has established that alkylamides are the only phytochemicals which are bioavailable from traditional lipophilic extracts of Echinacea root. In addition combining E. angustifolia with E. purpurea will enhance the alkylamide bioavailability of the latter and there is no difference (in terms of alkylamide bioavailability) between the tablet and liquid forms of Echinacea Premium.

 

The next question to be answered was whether the alkylamides do have an effect on the immune system. The MediHerb research team in collaboration with other scientists undertook test tube research to investigate such activity. The key findings of these studies were that:

 

  • Echinacea did not activate the immune system in the absence of any immunological challenge
  • The Echinaea alkylamides tended to modulate the immune responses of macrophages and T cells, toning the response down in the face of a strong stimulus, hence helping the immune system to operate more efficiently

 

This macrophage work was published as Stevenson LM et al in Molecules 2005; 10: 1279-1285 and the T cell study in Fitoterapia 2008; 79(1): 53-58.

 

A significant discovery, first presented at a major international conference, was the observation by two separate research teams that the immune effects of Echinacea may be mediated by the interaction of Echinacea alkylamides with cannabinoid receptors. A Swiss research team found that an in vitro immune-modulating effect of a lipophilic Echinacea extract (and individual alkylamides) on monocytes/macrophages could be neutralised by the presence of agents which block CB2 cannabinoid receptors.6 Bauer, in collaboration with US scientists, found that alkylamides from Echinacea bound to both CB1 and CB2 cannabinoid receptors.7 In particular, certain alkylamides exhibited selectivity for CB2 receptors.

 

Taken together, these developments first presented at the conference suggest the hypothesis that the alkylamides are largely responsible for the systemic immune effects of Echinacea lipophilic extracts and that this immune modulating activity is (at least in part) due to the interaction of alkylamides with cannabinoid receptors, specifically CB2

 

CB1 receptors are highly localised in the central nervous system (CNS) and are believed to primarily modulate behaviour, while CB2 receptors predominate in immune tissues outside the CNS, especially the spleen, and are believed to modulate immune function.8 Cannabinoid receptors are remarkably preserved across the animal kingdom which suggests they play an important developmental and physiological role.9,10 Much of the immune activity of the cannabinoid system appears to be mediated by the cytokine network. Cytokines include the interleukins (lL-3, lL-6, etc), tumour necrosis factor alpha (TNFα) and the interferons (IFN).

 

The Swiss team mentioned above has followed on from this ground-breaking research and shown that certain Echinacea alkylamides bind strongly to CB2 receptors.11 In addition they have shown that alkylamides also exert additional effects on immune cells which are independant of CB2.11 Their research has been particularly insightful into one aspect of the mode of action of Echinacea alkylamides.12 A lipophilic extract of Echinacea purpurea strongly stimulated TNFα mRNA synthesis in peripheral monocytes, but not TNFα protein production. In other words, the Echinacea-induced new TNFα transcripts (mRNA) were not translated into TNFα itself. When monocytes are treated with LPS (lipopolysaccharide or endotoxin, a powerful stimulator of the immune system) TNFα protein production is substantially inreased. However, co-incubation of monocytes with LPS and Echinacea extract resulted in a strong inhibition of this effect of LPS. This consistent with the findings of the MediHerb research team. 

 

Investigation over a longer time-span revealed that the lipophilic Echinacea extract, via interaction with CB2 receptors, modulated and prolonged TNFα production following immune stimulation.

 

The results of this study suggest that Echinacea works more as a modulatior or facilitator of the immune response, rather than as an immune stimulant

 

In resting monocytes it prepares them for a quicker immune response by inducing TNFα mRNA. However, in overstimulated monocytes (as in the case of LPS) it first reduces and then extends their response in terms of TNFα production. In particular, these key findings challenge the mythology that traditional Echinacea extracts will "overstimulate and wear out" the immune system if taken continuously.

 

Clinical Effects on immune Function

To further understand the effects of Echinacea Premium at a clinical level, a small study was undertaken to investigate its effects on heat shock proteins and whole blood parameters. Healthy volunteers were dosed with two Echinacea Premium tablets daily for two weeks, with assessment at the beginning and the end of the trial. Positive reults were evident, with increased heat shock protein levels (hsp70) and increades white cell counts. (Heat shock proteins are molecular chaperones which modulate the immune response). This work was published as: Agnew LL et al in Journal of Clinical Pharmacy and Therapeutics 2005; 30: 363-369. Further work is planned to further evaluate these effects in a much larger study.

 

This increase in white cell count for Echinacea Premium ties in well with research from the team of Dr Miller in Canada, which has shown (in experimental models) that E. purpurea root boosts the number and function of natural killer (NK) cells (a class of white blood cell).13 

 

The Story Continues

Adults travelling return from Australia to America, Europe or Africa on commercial flights via economy class took MediHerb Echinacea Premium tablets or placebo in a randomised, double-blind trial. Treatment began 2 weeks before flying overseas and finished 2 weeks after returning to Australia. The dose was one tablet twice daily, increasing to 2 tablets twice daily whilst flying. Participants were allowed to take a sick dose (3 tablets twice daily) if cold- or flu-like symptoms occurred. The sick dose could only be taken for up to 8 consecutive days or twice for 4 days during the whole travel period. Echinacea Premium was found to reduce the incidence of respiratory symptoms.

 

The research (by Tiralongo E et al) has been published (Evid Based Complement Alternat Med; 2012; 2012:417267).

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Further research is underway or planned in collaboration with Australian and European scientists:

 

  • Evaluation of the mechanism of immune effects in preparation in collaboration with the University of New England and Southern Cross University
  • Collaboration with researchers at Swiss Federal Institute of Technology and the University of Graz to further investigate the cannabinoid receptor findings

 

A New Understanding of Echinacea

The research on Echinacea Premium by the MediHerb scientists has made a substantial contribution to a new understanding of lipophilic extracts of Echinacea. It can be concluded from this research that:

 

  • Alkylamides must be used as the markers of quality and activity
  • The root of Echinacea is the preferred plant part, since it is highest in alkylamides
  • The preferred species of Echinacea are E. angustifolia and E. purpurea since they contain high levels of alkylamides (compared to E. pallida)
  • Echinacea must be extracted using an alcohol percentage sufficiently high to efficiently extract the alkylamides 
  • One potential way in which the bioavailable alkylamides modulate the immune response is by interacting with CB2 receptors
  • Echinacea root (rich in alkylamides) also boosts the white cell count
  • The traditional way Echinacea was used has been validated by scientific research at the cutting edge of modern immunology

 

Links to Echinacea Scientific Posters

 

NIH/MediHerb Echinacea Clinical Trial

Our research collaborations extend to the United States where we have a large scale National Institutes of Health (NIH) funded project to examine the efficacy of MediHerb’s Echinacea Premium tablets for the alleviation of the common cold. This project is a double-blind, placebo-controlled trial among the patients of the Verona Family Medicine Clinic, USA. This valuable trial will provide further evidence of efficacy that has already been demonstrated by a three-arm trial completed at the National College of Naturopathic Medicine in 1998. This earlier trial compared Echinacea Premium (standardised for alkylamides) to an adaptogen formula containing Korean Ginseng, Withania and Astragalus, and placebo in the prevention of winter colds over a three month period (MacIntosh et al, AANP Convention, Coeur d' Arlene, 1999). Those taking Echinacea Premium had a statistically significant (p = 0.03) decrease in winter infections when compared to placebo. The placebo group averaged an infection rate of 10% whereas the Echinacea group infection rate dropped to 2% at day 70. Ex vivo evidence of the efficacy of MediHerb Echinacea Premium for boosting immune function has also been obtained by researchers at the Royal Melbourne Institute of Technology (Francis et al, Australian Neuroscience Society, Melbourne, 2000).

 

NIH/MediHerb Bacopa Clinical Trial 

Another NIH funded trial is to investigate the use of Brahmi (Bacopa monnieri) for cognitive enhancement in an ageing population in collaboration with the Oregon Health & Science University. The principal investigator in this project, Dr Carlo Calabrese, approached MediHerb to supply a phytochemically characterised product and matching placebo for use in the trial (Calabrese et al, Journal of Alternative Complementary Medicine 2008; 14(6): 707-13).

 

For more information on the National Institutes of Health (NIH) see www.nih.gov.

 

More Trials

MediHerb has also donated herbal medicines and matching placebos for other clinical trials. We are able to offer a uniquely integrated service to trial investigators: research-driven product quality and manufacturing; pharmaceutical standard GMP; packaged products with blinding completed and all relevant documentation. Some of these trials include:

 

  • Several trials show the efficacy of Kava, eg for the treatment of Generalised Anxiety Disorder (Sarris J et al. J Clin Psychopharmacol  2013; 33(5): 643-648) and chronic anxiety (Sarris J et al. Psychopharmacology 2009; 205(3): 399-407) and it’s safety (eg Sarris J et al. Phytother Res 2013; 27(11): 1723-1728).

  • Valerian Complex for sleep problems in older adults (Royal Melbourne Institute of Technology)
  • Formulated product for ADHD (Royal Melbourne Institute of Technology)
  • Horsechestnut for venous leg ulcers (University of South Australia)
  • Cognition enhancement in healthy students (University of Tasmania)
  • Formulated product for menopause (Royal Melbourne Institute of Technology)
  • Mexican Valerian for sleep difficulties in children with intellectual deficits (Royal Melbourne Institute of Technology) (Francis A, Dempster R. Phytomedicine 2002; 9(4): 273-279)

 

Clinicalfeeback V1

Clinical Feedback Trials

Clinical feedback trials involve our practitioners in the development and validation of new products prior to launch. By working together we are able to gather valid clinical data in a timely and cost-effective manner. Feedback trials were completed

 for Saligesic (a highly potent willow bark product for the symptomatic relief of lower back pain) and Cramplex (a formulated product for the symptomatic relief of dysmenorrhoea) prior to their launch. The data generated from these trials is depicted in the graphs and clearly demonstrates their efficacy.

 

Phytochemical Investigations

Understanding the complexities of the phytochemicals within herbs is fundamental to quality and efficacy. Once these are defined and identified through extensive laboratory analysis, quality assurance procedures can be established to ensure that the same premium quality raw material is consistently used.

 

A complicating factor of phytochemical analysis is the concept of marker and active compounds:

 

  • A marker is a characteristic phytochemical found in a herb plant that is chosen to represent a quality standard
  • An active is a phytochemical that is important for a given therapeutic effect of a herb

 

A marker compound may or may not be responsible for any therapeutic efficacy of the herb. A vast amount of phytochemical data has been compiled on various plant species from around the world, but there is a relative scarcity of data relating to the identification of active constituents. This is partly due to the often observed finding that the therapeutic action of a herb is due to the synergy of multiple phytochemicals, rather than just one isolated component.

 

MediHerb, in conjunction with the University of Queensland, is currently involved in a research project investigating the phytochemical profile of poorly-defined medicinal plants. This ground-breaking research has already provided some interesting data on widely used herbs whose phytochemical profile has previously been poorly understood, for example:

 

False UnicornChamaelirium Luteum

A unique steriodal saponin has been identified in Chamaelirium luteum (False Unicorn) that is not found in any other medicinal herb. This unique phytochemical could be the key to False Unicorn’s therapeutic effect.

 

Paeonia

In Traditional Chinese Medicine, the roots of Paeonia lactiflora (Paeonia) are typically bleached. Investigation into the affect of bleaching the roots has shown that the active constituent paeoniflorin, is modified into a stable new compound paeoniflorin sulfonate.  

The elucidation of the structure has been published in Tetrahedron Letters 2005; 46: 2615-2618 and the HPLC method to allow identification of this modification by other manufacturers has appeared in Phytochemical Analysis: (2006) 17: 251-254.

 

Wild Yam

The phytochemical profile of Wild Yam is based on scientific literature from the 1940s. MediHerb undertook a project in conjunction with Associate Professor James De Voss, Chemistry Department, University of Queensland to investigate the phytochemistry. It is widely misconstrued that Dioscorea villosa contains diosgenin and many products have this as a statement on their labels. However it does not contain diosgenin, but rather the diosgenin precursors. Traditionally Dioscorea villosa was believed to contain predominantly dioscin, however, the origin of this assignment is unclear (dioscin is a steroidal glycoside precursor of diosgenin). Commercially available Dioscorea villosa is in the form of dried roots, usually harvested at the end of summer or autumn when the plant is dying back to its rootstock. It was found that these roots contained only very small amounts of dioscin, not the predominance as previosly thought. The major saponin found in the autumn harvested roots were in fact the furostanol-based saponins, methylparvifloside and methylprotodeltonin. While the spirostanol-based saponins, Zingiberensis saponin I and deltonin were the major saponins for samples harvested in summer. Further work continues. It is alarming that such a widely used herb is so misunderstood and commonly substituted. 

 

Shatavari

Prior to 2005, Shatavari was not on the Register of Therapeutic Goods which meant that it was only available in liquid extract form to practitioners. MediHerb recognised the clinical importance of Shatavari also being available in a tablet. MediHerb undertook a two year process to prepare the required TGA submission, which required careful investigation into the phytochemistry of Shatavari to be conducted. MediHerb's collaboration with the research group of Associate Professor De Voss from the Chemistry Department of the University of Queensland revealed that the structures of the main saponins were incorrectly reported in the literature. Three research papers have been accepted for publication:Tetrahedron Letters 2006; 47: 6965-6969 & 8683-8687 and Phytochemistry 2008; 69(3): 796-804.

 

Garlic Allicin Release

Garlic

It is now considered to be a requirement for publication of clinical trials that the phytochemical constituents of the formulation be known and they must be included in the submission. Variations in the phytochemical constituents is believed to be responsible for the varied clinical results obtained in many trials. An analysis of Garlic trials (Lawson et al, J Agric Food Chem 2001; 49(5): 2592-9) has linked the efficacy of Garlic formulations to those containing a high level of allicin release. However, in many early trials this information was not provided, either because it was not available or was proprietary.  

 

Anthelmintic Herbs

A project investigating the phytochemical characterisation of herbs with anthelmintic activity was conducted in conjunction with the Chemistry Department of the University of Queensland and the Department of Primary Industries. This project involved a PhD student and a postdoctoral researcher and targeted the identification of herbs with high anthelmintic activity and the constituents of those herbs responsible for this activity. The results of this research led to the reformulation of MediHerb’s Wormwood Complex tablets.

 

Agronomic Research

Research programs on the growing and post-harvest of herbs have been undertaken at a range of academic institutions, most with the support of the Australian Government under the Rural Industries Research and Development Corporation (RIRDC) grant scheme. These projects look at the importance of varietal selection, soil and climatic conditions, harvest time, post-harvest drying methods and storage in herb quality and efficacy. Projects under the RIRDC scheme have included three-year PhD research grants for the optimisation of Echinacea purpurea (in conjunction with the University of Newcastle), a study of Matricaria recutita (Chamomile) at the University of Tasmania, and examination of Valeriana officinalis (Valerian) at the University of Newcastle. Another project has recently been completed in collaboration with the Research Institute of Agroecology in Slovakia,  investigating the optimal growth conditions for Tribulus terrestris (Tribulus).

Synara Scolymus

 

Many smaller projects have centered on the optimisation of other herbs within the MediHerb range. One such example is Cynara scolymus (Globe Artichoke). Globe Artichoke contains a mixture of caffeoylquinic acids and flavonoids that contribute to its clinical effect. These were found to be quite variable in the raw materials sources by MediHerb. A research project was initiated to investigate the cause of variability, looking at varietal differences, geographical effects, harvest parameters, and post-harvest handling. It was found that by optimising the post-harvest handling of the Global Artichoke leaves it was possible to increase the level of desirable phytochemicals by a factor of six.

 

By optimising the post-harvest handling of Globe Artichoke the levels of phytochemicals were increased by a factor of six

 
References
1. Wagner H. Herbal immunostimulants. Z Phytother 1996; 17(2): 79-95
2.  Felter HW, Lloyd JU. King's American Dispensatory. 18th Edn, 3rd revision. First published 1905, reprinted Eclectic Medical Publications, Portland, 1983.
3.  Ellingwood F. American Materia Medica, Therapeutics and Pharmacognosy. Eclectic Medical Publications, Portland, 1993.
4.  Bauer R, Wagner H. In Wagner H, Farnsworth NR eds. Economic and Medicinal Plant Research, Vol 5, Academic Press, London, 1991.
5.  Melchart D, Clemm C, Weber B et al. Polysaccharides isolated from Echinacea purpurea herba cell cultures to counteract undesired effects of chemotherapy - a pilot study. Phytother Res 2002; 16: 138-142
6.  Gertsch J, Schoop R, Kuenzle U et al. Alkylamides from Echinacea purpurea potently modulate TNF-alpha gene expression: Possible role of cannabinoid receptor CB2, NF-DB, P38, MAPK and JNK pathways. International Congress on Natural Products Research,  Phoenix, Arizona USA, July 31-August 4, 2004, Lecture 0:9
7.  Woelkart K, Xu W, Makriyannis A et al. The endocannabinoid system as a target for alkamides from Echinacea roots. International Congress on Natural Products Research, Phoenix, Arizona USA, July 31-August 4, 2004, Poster P:342
8.  Ralevic V. Cannabinoid modulation of peripheral autonomic and sensory neurotransmission. Eur J Pharmacol 2003; 472(1-2): 1-21
9.  Salzet M, Breton C, Bisogno T et al. Comparative biology of the endocannabinoid system possible role in the immune response. Eur J Biochem 2000; 267(16): 4917-4927
10.  Fride E. The endocannabinoid-CB receptor system: Importance for development and in pediatric disease. Neuro Endocrinol Lett 2004; 25(1-2):24-30
11.  Raduner S, Majewska A, Chen J-Z et al. Alkylamides from Echinacea Are a New Class of Cannabinomimetics. J Biol Chem 2006; 281(2): 14192-14206
12.  Gertsch J, Schoop R, Kuenzle U et al. Echinacea alkylamides modulate TNF-α gene expression via cannabinoid receptor CB2 and multiple signal transduction pathways. FEBS Letters 2004; 577(3): 563-569
13.  Miller SC. Echinacea: a miracle herb against aging and cancer? Evidence in vivo in mice. eCAM 2005; 2(3): 309-314