When we turn to modern sources, we may imagine that the internal use of burdock for boils echoes the old topical use. However, an antimicrobial action would be desirable to support this action, and this has been linked to poly-acetylenes found in fresh burdock root, whereas the classical authors wanted the leaves to be applied topically. Weiss considers the root the most important part of the plant for medicinal use but does not consider its action to be very great and recommends its use only in combination with other herbs. This could include cystitis, as listed by other authors. An oil made from the root can be used, says Weiss, to stimulate hair growth in alopecia and for dry seborrhoea. Mills and Bone also discuss only the root. Wood and Menzies-Trull include the seeds as well, perhaps following the recommendation by Priest & Priest of the seeds, especially in skin conditions. Pelikan highlights the fact that it is only the flower heads of burdock, and its fruit or seed, which display the thistle aspect of the plant. The leaves and root, on the other hand, are rich in mucilage, which he regards as evidence of their ‘struggle against spiny hardness’. Here we have an image to link with the several recommendations for the use of burdock in dry skin conditions. Wood notes that burdock root is bitter, sweet and oily, so well suited to dry and atrophic states with constipation and poor emulsification of dietary fats and oils, and in general it helps those persons suffering from long, chronic illness. Pelikan states that burdock shows great vitality in overcoming poor soil conditions.
Owing to the bitterness of the plant burdock is credited by Williamson with laxative and appetite-stimulating effects. For the same reason Menzies-Trull adds central nervous system stimulation, and lists also circulatory and lymphatic stimulant and anti-fungal actions. Hoffmann sees an enhanced indication in rheumatic complaints associated with psoriasis, presumably psoriatic arthropathy Priest & Priest want the root to be prescribed with ginger Zingiber officinale for rheumatism and gout, and with golden seal Hydrastis candensis for a tonic effect in vaginal laxity, a use which recalls the old indications of leucorrhoea and menorrhagia. The British Herbal Pharmacopoeia suggests combinations of burdock root and curled dock root Rumex crispus or red clover flowers Trifolium pratense in skin disease, and while the herb has a separate entry from the root, its actions are noted as similar to lappa root, with specific indications as use as poultice for boils and abscesses.
Burdock is the main herb in Essiac tea which is amongst the many products used in the hope of treating and preventing reoccurrence of cancers. Herbalists customarily use alteratives in the care of patients with cancer, and burdock is considered the alterative par excellence. Essiac was developed in Canada by Rene Caisse after her aunt became ill with cancer (History of Essiac 2007). Rene Caisse was a nurse and treated patients with cancer at the clinic in Ontario which she set up and ran from 1934 until 1942. The preparation was recommended by a miner’s wife who had been treated for a breast tumour by a Native American in the early 20th century.
The four original herbs in Essiac are burdock root Arctium lappa, small pieces (32 parts by weight), sheep sorrel Rumex acetosella, powder, (16 parts), slippery elm bark Ulmus fulva, powder (4 parts) and turkey rhubarb root Rheum palmatum, powder (1 part). The dried herbs are mixed together and batches can be made using 1 cup (8 fl oz) of dried herb in 2 gallons of distilled water. (The US fluid ounce is slightly larger than the imperial fluid ounce). The recipe is made up taking one part as 5 g, making a total of 265 g in 1800 mL of water. The water is brought to a rolling boil in a pan with the lid on, and then the dried herbs are added, the water is brought back to the boil and boiled for 10 minutes. The mixture should be stirred and the pan left undisturbed overnight. After reheating to steaming hot, the mixture is allowed to cool slightly before it is strained through a cloth. Portions of 30 mL, the quantity of one dose, may be frozen for taking when required in 60 mL of hot water, once daily at bed time on an empty stomach. Food should not be eaten within an hour either before or after taking the tea. The yield from 1800 mL was in one experiment 1600 mL, which gave a dose of just over 3 g of dried burdock in 30 mL. There has been debate concerning the herbs employed and their proportions in the Essiac mixture. An affidavit given by Mary McPherson, who worked with Rene Caisse, proposes slightly different proportions (Essiac Info 2009). Turkey rhubarb does not grow in North America and the original herbs are said to have grown wild, which has led to the suggestion it might have replaced a species of Polygonum (Essiac Info 2009). The formula given by Bartram suggests continuing the mixture for 32 days, then every third day. Bartram’s formulation differs very slightly in the quantities and he intends the formula for cancers of the stomach and intestines only.
Essiac and similar formulations such as Flor-essence are now widely available (Cancer Research UK 2008, Medline Plus 2008). Flor-essence has the same four ingredients plus four more, including red clover, and, for the sake of clarity, this review does not refer to any studies on Flor-essence although there has been substantial investigation of its use in Russia in gastrointestinal disease. There have been some unpublished studies on Essiac but the only randomized controlled trial investigated quality of life. This is not relevant as Essiac is generally taken with the intention of influencing the progression of the disease.
Natural compounds have been shown in vitro to inhibit various stages in cancer and, given the widespread usage of Essiac, it is worth discussing whether it could promote remission in cancer and whether it is safe. A useful review of the herbs in Essiac was undertaken by Tamayo et al (2000), although we can find no evidence to support their statement that there are isoflavonoids in burdock root. In vitro investigations on burdock and Essiac are now reviewed to see whether they provide any support for the use of Essiac. Conflicting points of view are expressed and an array of in vitro studies are used in the literature to support the use of Essiac, but the discussion illustrates the problems in relying on in vitro evidence to support claims for efficacy.
Studies on burdock have shown antioxidant and anti-inflammatory activity and it is argued that this is associated with anticancer activity. A recent study found a strong correlation between total polyphenol concentration in burdock root, seed and leaf and antioxidant activity (Trolox assay). The seeds showed greatest antioxidant activity whereas the root had hardly any activity. This study is useful as all three parts were assayed using the same methodology at the same time. In contrast, an in vitro study on burdock root found antioxidant actions: scavenging of free radicals (DPPH assay) and inhibition of oxidation of linoleic acid. Comparison of aqueous extracts from peeled and unpeeled root showed that antioxidant activity (DPPH assay) was greater in unpeeled roots, and this appeared to be associated with the concentration of chlorogenic acid, which is a phenolic acid found in many herbs and foods and is not particular to burdock.
Three further studies investigated the antioxidant activity of Essiac. It was found to scavenge effectively hydroxyl
(Fenton reaction) and superoxide radicals (xanthine/ xanthine oxidase assay), and prevent hydroxyl radical-induced lipid peroxidation. A criticism of this study is the high concentration of Essiac used as the preparation was a 1:2 Essiac tea. Essiac showed significant antioxidant activity (ABTS assay). In the third study, Essiac showed both antioxidant (TEAC assay) and proinflammatory actions such as induction of tumour necrosis factor-alpha (TNF-alpha), interleukin-1 beta (IL-1 beta) and cyclooxygenase-2 (COX-2).
Essiac uses burdock root. However, let us turn to the in vitro studies on the lignan arctigenin (aglycone of arctiin), which is found in burdock seed, as these studies are mentioned in reviews of Essiac. They are only relevant to use of the seed as arctigenin is found only at very low concentration in the root. To illustrate the complexity of in vitro methods, the following examples are given. Some studies can be compared as they use one model to measure anti-inflammatory activity. Inhibition of lipopolysaccharide (LPS) induced nitric oxide production by a murine mac-rophage RAW 264.7 cell line is used as a measure of inflammatory activity. Excess nitric oxide production by nitric oxide synthase (iNOS) occurs in macrophages in response to proinflammatory stimulation such as IL-1 beta, TNF-alpha and LPS. Lignans, in particular diarctigenin and lappaol-F, were shown to inhibit this process. In a study using this model, arctigenin inhibited nitric oxide production and secretion of the proinflammatory cytokines TNF-alpha and IL-6 in a dose-dependent manner. Arctigenin was found to inhibit expression and activity of iNOS, but not to inhibit COX-2 expression and activity.
Another team also found inhibition of induction of iNOS using the same mechanism and associated this with the concentration of arctigenin in the seed. They found this inhibition was caused by inhibition of nuclear factor kappa B, which is activated in inflammatory responses to viral and bacterial infection and is involved in the production of iNOS and TNF-alpha. The same team also found that arctigenin inhibited mitogen-activated protein kinase and argue that this shows that arctigenin inhibits cellular responses to extracellular signals such as gene transcription. This results in inhibition of activator protein-1, which is associated with cell proliferation, differentiation and apoptosis. Inhibition of activator protein-1 is thought to result in reduction in production of TNF-alpha m-RNA in cells exposed to LPS and thus reduction in TNF-alpha production by macrophages. The detail is given here to demonstrate the complexity of in vitro methods and thus the risk in making claims based on any one study. To conclude, antioxidant activity in burdock is associated with overall concentration of polyphenols and is highest in the seeds, but also found in leaves and root. If this finding is linked with the concentration of lignans, then the seeds are the most useful part.
Another line of enquiry has been to investigate the effects of burdock and Essiac on cancer processes. For example, an in vitro study using the LNCaP prostate cancer cell line found that proliferation was inhibited by Essiac. Another study using LNCaP cells found that growth was inhibited by the lignans lappaol A, C and F isolated from burdock seeds and the authors argue that this could support the use of Essiac. However, it would actually support the use of burdock seed not of the root. A further study found no antiproliferative activity for Essiac in prostate cancer, whereas dose-dependent inhibition of seven cancer cell lines was shown by Seely et al (2007).
In contrast, Essiac at a range of concentrations was shown to actually stimulate cell proliferation relative to untreated controls in four breast cancer cell lines, both oestrogen receptor positive and oestrogen receptor negative. The authors discuss their methodology to consider why these results differ from other studies. For example, they note the high levels of Essiac extract used in another study which found an antiproliferative activity in breast cancer cells (MCF-7). In a further study, a metabolite of arctiin formed in the gut showed a proliferative effect on the growth of MCF-7 breast cancer cells, but inhibited estradiol-mediated proliferation of the same cells to a similar degree as tamoxifen. In this study, the metabolite of arctiin appears to have had opposing actions depending on the presence of oestradiol. This interesting research again demonstrates the complexity of in vitro research and the danger of extrapolating the results of any one study to the living body in order to support the use of any medicinal plant.
As the lignans are found in the seeds, studies on arctigenin are not applicable to the use of Essiac, and most studies on the antiproliferative activity of burdock seeds are on the activity of arctigenin. This raises the question of which part of burdock should be used but it also asks whether any in vitro study supports the oral use of burdock. In many cases, we do not know about the absorption of the constituents of herbs. However, in the case of arctigenin there is evidence from pharmacokinetic studies on the uptake and absorption of lignans to show that it is not absorbed into the body. The lignan content and activity of linseed Linum usissitatum has been investigated and is relevant to burdock. The main lignan in linseed is secoisolariciresinol, which has been found to be transformed by bacteria in the proximal colon to enterodiol and enter-olactone, which are then absorbed into the body. The same team found that incubation of arctiin with a human faecal suspension for 9 days led to the formation of six metabolites, and the enterolactones formed were enan-tiomers of those produced by linseed. In this study, the breakdown of arctiin was gradual and it could be argued that it supports the usage in Russia for gastrointestinal conditions referred to by Tamayo et al (2000) as the metabolites may have local effects in the gut.
The above studies seem neither to support nor oppose the use of burdock or Essiac in cancer. The study on breast cancer cells could be important but one can conclude that this finding is not associated with lignans, which are considered to be phytoestrogens as the lignan level is low in burdock root. In addition, it is thought that lignans in the diet may reduce oestrogen levels in postmenopausal women and be protective against hormone-dependent cancers. The absorption of lignan metabolites has been studied extensively and the concentration in the blood depends on the diet, bacterial metabolism and conjugation in the intestinal wall and liver but none of these factors explain interindividual variation in blood concentration of enterolactone. If lignans are sought in the diet then oilseeds especially linseed and sesame seeds and wholegrain cereals are important sources. Arctigenin may have unique actions but otherwise dietary recommendations are more important in this regard than the use of burdock as a herbal medicine.
We found no adverse drug reports on Essiac and, although some reviews make exaggerated claims for the possible effectiveness of Essiac based on in vitro studies, maybe the main conclusion is that appraisal of the traditional evidence for use of burdock as an alterative is of equal value in supporting the use of Essiac.