Critical Review of Tarragon's Traditional Use, Chemical Composition, Pharmacology, and Safety
Obolskiy D, Pischel I, Feistel B, Glotov N, Heinrich M. Artemisia dracunculus L. (tarragon): a critical review of its traditional use, chemical composition, pharmacology, and safety. J Agric Food Chem. 2011;59(21):11367-11384.
Tarragon (Artemisia dracunculus) has been widely used traditionally as both a spice and medicinal plant. This species is a small, aromatic shrub endemic to North America, Europe, and Asia with cultivation occurring in Europe, Russia, and the United States. Tarragon is described in ancient texts for the flavoring of foods as well as for treating scurvy, arthritis, and urogenital problems. This review aims to critically evaluate current data on the phytochemical content and bioactivity of tarragon with a focus on potential future uses of this plant.
Despite the broad, traditional uses of tarragon, different varieties, mainly the French (A. dracunculus) and Russian (A. dracunculus syn. A. dracunculoides) cultivars, vary in their phytochemical composition, bioactivity, and chromosome count. The review assesses the considerable taxonomic confusion at the subspecies level. Thus, rigorously identifying original material is important in future tarragon research. The French and Russian varieties of tarragon taste different; the former is thought to be sweeter and more "delicate" than the latter, more "bitter and harsh" flavored counterpart. The species is used in many foods, from meat and fish flavoring to vinegars and drinks. Medicinally, people in the Middle East have used tarragon for insomnia, while those in Asia and Russia applied it for various skin ailments. People in India treated fevers with tarragon; and Native Americans used it for labor assistance, mosquito repellent, and treating cuts. In areas throughout the former Soviet Union, tarragon was used for nervous problems, as an anti-inflammatory, and to treat bacterial infections. French tarragon is considered of more economic importance than Russian, given its pleasing culinary properties. In Europe, it is one of the 20 most commonly cultivated herbs.
The prominent compounds in tarragon have been found to be coumarins, flavonoids, and phenolic acids. A large focus of phytochemical research of tarragon has been on the essential oil. The oil content is variable depending on geographical location and is produced mostly during budding and initial flowering. The essential oil primarily contains acetylene chemicals, isocoumarin derivatives, fatty acids, and the specific compounds methyleugenol, estragole, elemicin, and terpinolene. Russian tarragon mainly contains terpinen-4-ol, sabinene, and elemicin, while French tarragon contains higher amounts of estragole than the Russian cultivar. An extensive table that details the components of the essential oils in tarragon is included.
Multiple bioactivities of tarragon have been reported in vitro. Tarragon chloroform, acetone, methanol, and water extracts have been found to be active against a variety of bacteria including Staphylococcus aureus, Pseudomonas aeruginosa, Shigella, Bacillus subtilis, Listeria monocytogenes, and Helicobacter pylori. In addition, the essential oil was active against several fungal species, including those that infect plants. In vitro studies also reported that tarragon leaf extract showed activity against platelet adhesion and aggregation.
In vivo work on the bioactivity of tarragon explores a variety of targets. Ethanol extracts were found to be anti-inflammatory and reduced rat edemas by 80%. This extract also reduced hepatitis-induced necrosis in rats by more than 30%. The suspected mechanisms of action involve beneficial effects on hepatocyte cell membranes and compensatory mechanisms. Many animal studies show decreased glucose concentrations; these results were also observed with an oral glucose tolerance test, adrenaline-induced elevated glucose, and alloxan or streptozotocin models. Mechanisms of hypoglycemic activity of tarragon include kinase stimulation, the increase of GLP-1 (glucagon-like peptide 1) binding, the inhibition of gluconeogenesis (internal synthesis of glucose), and the amplification of endogenous insulin. Tarragon has also been found to have antioxidant activity. A study found evidence that tarragon extract lessened lipid peroxidation, and the essential oil was reported to have "moderate" in vitro scavenging activity. Additionally, ethanol, but not water extracts, lessened death from anoxia (oxygen deprivation) in rats.
Tarragon showed a very strong effect on the gastrointestinal system with the ethanol extracts stimulating gastric juice secretion and preventing induced ulcers in rats. The dried extract and infusion of tarragon was reported to decrease hepatic transaminase activity (high levels of which can indicate liver damage or illness), and extracts were found to lessen liver necrosis.
The neurotropic activity of tarragon has also been explored. In rats, a preliminary investigation of tarragon extract was found to lengthen thiopental-induced sleep, and water/alcohol extracts had beneficial effects on orientation, emotional lability, and decreased exploratory behavior. Tarragon extract was also reported to have analgesic effects. Anticonvulsant activity was reported with the distilled essential oil, but as the active dosage was not much lower than the lethal dose, questions arose concerning toxicity of the oil. An extensive table outlines the studies on the physiological effects of tarragon, including the compound used, its origin, the model it was tested in, the dose used, and the outcome.
In terms of the safety profile of tarragon, investigative focus has concentrated on the prevalent compounds estragole and methyleugenol. Estragole has been found to cause tumors in rodent models, as well as cancer in specific animals and tissues. Later studies have pointed to cancer-causing metabolites of estragole as opposed to the compound itself. The metabolism of compounds can differ from animals to humans, and it is currently thought that the risk of estragole acting as a carcinogen in humans is small. Methyleugenol is a widely active carcinogen and has been reported to consistently cause tumors in multiple rodent models and tissues. Despite the carcinogenic activity of these 2 compounds, water, water/alcohol, and ethanol extracts which contain very low amounts of estragole and methyleugenol have shown neither mutagenic nor toxic activity in rodents. Overall, such extracts can, therefore, be considered to be safe.
This review includes a large number of Russian and Soviet studies that contribute to extensive investigation of tarragon bioactivity. Many of the pharmacological activities described are worthy of further research using taxonomically and phytochemcially fully characterized material, not the least of which is the hypoglycemic activity. It is emphasized that proper identification of tarragon cultivars is crucial in assessing its bioactivity. Although strong carcinogenic activity is reported for isolated compounds, the use of water extracts of tarragon as a tea or spice is considered to be safe due to the low content or absence of estragole and methyleugenol. Future robust clinical investigations into the use of tarragon for treating a variety of diseases are recommended.
—Amy C. Keller, PhD
Russian Tarragon Artemisia dracunculus Family: Asteraceae
INTRODUCTION
Russian tarragon is a perennial herb of the daisy family native to parts of southern and eastern Russia, Afghanistan, Mongolia, and western North America; it was introduced via cultivation in parts of Central Europe and North America.1 Known variously as Russian, Siberian, and wild tarragon, it is one of two reported cultivars in the species Artemisia dracunculus. The other is French tarragon, A. dracunculus ‘Sativa’.1,2 Russian tarragon is seed-fertile, has an odor described as balsamic and leathery, and rarely is used for cooking. French tarragon is seed-sterile, propagated by vegetative or clonal propagation, and is preferred for culinary use due to its flavor which is likened to anise (Pimpinella anisum, Apiaceae) or basil (Ocimum basilicum, Lamiaceae).1-3 Russian tarragon is described as having a distinctly bitter taste.4
The authors of this article have made their best effort to make sense of the literature on A. dracunculus and include only information they could positively identify as referring to “Russian” tarragon. However, as the author of one article on A. dracunculus stated, “…the existing literature lacks a common approach to the species’ taxonomic classification, with some authors classifying French tarragon and Russian tarragon as subspecies, varieties, or even species.”3 Synonyms for A. dracunculus include A. dracunculus f. redowskii hort, A. dracunculus ssp. dracunculoides, A. dracunculoides, and A. dracunculus var. dracunculus, among others. Additionally, there is a wide range of morphological and phytochemical variability within the species (cytotypes) dependent upon geographical origin of samples studied. Russian botanical textbooks reference six varieties of A. dracunculus throughout the former Soviet Union alone.3 Thus, a clear and complete understanding of the source material is difficult to guarantee. However, according to the USDA Germplasm Resources Information Network (GRIN) classification, A. dracunculus is not separated into subspecies or varieties.4
HISTORY AND CULTURAL SIGNIFICANCE
The genus name Artemisia may refer to the ancient deity Artemis Eileithyia, a Greek goddess of childbirth.5 Another interpretation suggests that it may refer to Queen Artemisia II of Caria (died ca. 350 BCE), the sister, wife, and successor of King Mausolus of Caria (a region of western Anatolia in modern-day Turkey), and a botanist in her own right.2,5 Another possible origin story refers to Artemis, the Greek goddess of the moon, chastity, wilderness, and the hunt, who gave this plant to Chiron the Centaur, a great healer who then developed medicines from Artemisia.2,5 The specific name dracunculus means little dragon or snake and is thought to refer to the plant’s roots which resemble coiled serpents or, perhaps less likely, the resemblance of the leaf’s shape to a dragon’s tongue.1,3,5 Another explanation for the species name may come from a former use of tarragon as an antidote for snake bites.5 However, it might also be that tarragon was used for snake bites due to the species name and appearance of the roots, in accordance with the Doctrine of Signatures (the traditional practice of inferring a plant’s actions/uses based on its color and/or shape, or giving a plant a mnemonic name based on its known use).6 The common name tarragon may come from the Greek tarkhōn (or tarchōn), the Arabic ţarhūn (or tarkhūn), and/or the Latin tarchon, all terms referring to dragons.7
Nicholas Culpeper, the 17th century herbalist and physician, mentions tarragon (Russian or French not specified) as being heating and drying, and its use as a remedy for urogenital issues, “the flux, or any preternatural discharge … and gently [promoting] the menses.”8 Johann Georg Noel Dragendorff, 19th century German pharmacist and chemist, in his 1898 treatise on medicinal plants, mentioned tarragon (Russian or French not specified) for its urogenital, anti-arthritic, and antiscorbutic (anti-scurvy) uses.3
Although Russian tarragon is not preferred for culinary use, it is eaten in Iran to stimulate appetite.9 It is also used as a digestive stimulant and to flush toxins from the body, for insomnia, to dull the taste of medicines, and to ease the pain of sores, cuts, and toothaches.3 Russian tarragon has been employed in Azerbaijan as an antispasmodic, laxative, and to treat epilepsy and intestinal gas. It also has been used topically in Russia and Central Asia for dermatitis, rashes, and wounds, and in India to treat fever and worms. Other traditional uses in the former Soviet Union include aiding digestion, nervous conditions, for liver and renal function, and as antibacterial, anti-cancer, and anti-inflammatory agents.3
In North America, where it naturalized, various Native American tribes employed Russian tarragon for myriad conditions. It was used internally for treating dysentery (root); colic (root); urinary problems (root); colds (cold infusion of root); as a stimulant (decoction of leaves and roots in bath); as an abortifacient (infusion of root or leaf and stalk); for excessive menstrual flow (root decoction); for difficult labor (whole plant decoction); heart palpitations (leaf and flower infusion or fresh leaf chewed); to make babies stronger (root decoction bath); to make the elderly stronger (root decoction steam); and as a general tonic (infusion of roots).10 Externally, Native Americans used the plant for, among other things, eye conditions (infusion of stems and leaves or poultice of leaves); for rheumatism (infusion of foliage, steam bath with leaves, or decoction of whole plant as a liniment); open sores (foliage, dried and powdered); headache (poultice of mashed, dampened leaves); diaper rash/raw skin (leaves); bruises (infusion or decoction of plant in bath); and hair growth (compound root decoction).10
CURRENT AUTHORIZED USES IN COSMETICS, FOODS, AND MEDICINES
In the United States, A. dracunculus, whether French or Russian, is classified by the Food and Drug Administration (FDA) as a spice, natural seasoning, or flavoring that is generally recognized as safe (GRAS) for its intended use in food products. The essential oil and natural extractives are also listed as GRAS substances.11
There are also Russian tarragon-containing dietary supplement products in the US market, especially in the athletic performance enhancing category. For example, SLINshot™ (Purus Labs, Inc.; Dallas, TX) is labeled as containing 1,000 mg per serving (two capsules) of a dried aqueous extract of A. dracunculus L. var. inodora standardized to 0.2-0.7% flavonoids as 2-(3,4-dihydroxyphenyl)-5,7-dihydroxy-4-oxo-4H-chromen-3-yl D-galactopyranoside.12
In Canada, both A. dracunculus dried or fresh plant material, whether French or Russian, and the essential oil of A. dracunculus (tarragon oil) are classified as medicinal ingredients of licensed natural health products (NHPs) requiring pre-marketing authorization from the Natural Health Products Directorate (NHPD) and manufacture in compliance with NHP GMPs. Tarragon oil additionally is permitted for use as a non-medicinal component of NHPs (at non-therapeutic levels) for functions including flavor enhancement, as a fragrance, and for skin-conditioning.13
At the time of this writing there were three licensed NHPs in Canada containing A. dracunculus as a medicinal ingredient including two athletic performance enhancing combination products, “Creatine Rt” powder (Peak Performance Products Inc.; Toronto, Ontario) and “Big C” capsules (Magnum Nutraceuticals Inc.; White Rock, British Columbia). Two licensed NHPs presently list tarragon oil as a non-medicinal ingredient.14
Similarly, in Australia there are listed medicines that contain extracts of A. dracunculus as an active ingredient with marketing authorization granted by the Therapeutic Goods Administration (TGA), including the athletic performance enhancing product “Creatine Plus Endura” powder (Health World Limited; Queensland).15
There are presently four A. dracunculus ingredients authorized for use in cosmetic products by the European Commission Health and Consumers Directorate. The essential oil of the whole herb is listed for perfuming and skin conditioning functions, the herb extract for perfuming function, the leaf and stem extract for masking function, and the root extract for skin conditioning function.16
MODERN RESEARCH
As mentioned previously, different geographical origins of A. dracunculus samples result in morphological and phytochemical variability. In addition, as a polyploid taxon (i.e., having two complete sets of chromosomes), A. dracunculus cytotypes differ in external morphology, phytochemical constituents, anatomy, and fertility.3 Divergent phytochemical profiles suggest that standardization of plant material would be required in order to duplicate results in medicinal applications.
Most of the scientific data on A. dracunculus comes from either pharmacological or animal studies. However, a few small human studies have investigated Russian tarragon for its potential as an adjunct therapy in diabetes and athletic training.
Laboratory tests have confirmed that extracts, essential oil, and individual compounds of A. dracunculus have antioxidant, antibacterial, antifungal, antimicrobial, and antiplatelet activities, and may be useful in addressing metabolic syndrome.3,17-19 Much of the research has addressed the composition of its essential oil, which contains coumarins, flavonoids, and phenolic acids.3,18 While the essential oil of Russian tarragon can contain up to 30% methyl eugenol and very low levels of estragole — chemical constituents considered to be potentially harmful — neither ethanolic nor aqueous extracts contain such levels, making them safe alternatives in food and medicine.20
A 2011 randomized, double-blind, crossover study of 12 non-diabetic men investigated the effects of an aqueous extract of Russian tarragon (RT) on serum glucose and insulin in an oral glucose tolerance test.21 Participants visited a lab on two mornings separated by one to two weeks where they ingested either two grams of RT (dried aqueous extract standardized to 0.2% to 0.7% total flavonoids; Finzelberg GmbH & Co. KG; Andernach, Germany) or placebo. Blood was drawn before ingestion of RT or placebo and at 15, 30, 45, 60, and 75 minutes after ingesting the dextrose load. Participants taking RT displayed a non-statistically significant lowering of blood glucose and a slightly lower insulin response. The authors state that additional studies are needed with a larger sample of individuals with pre-diabetes and untreated diabetes.
In 2013, a poster presentation at the 10th Annual International Society of Sports Nutrition Conference and Expo addressed a very small randomized, double-blind study exploring the effect of A. dracunculus on resistance training adaptations.22 In the study, 12 resistance trainers (eight male, four female) consumed supplements for eight weeks of either six grams per day creatine plus 1100 mg per day A. dracunculus extract (no additional information provided) plus 40 grams per day collagen plus 0.38 grams per day fruit punch flavoring (Cr+RT, n=3), or 90 grams per day dextrose plus 0.38 grams per day fruit punch flavoring (PL, n=5), or 84 grams per day dextrose plus 6 grams per day creatine plus 0.38 grams per day for fruit punch flavoring (Cr+CHO, n=4). During the study, participants performed resistance training four days per week. After four weeks, the increases in lean body mass were significantly higher for the Cr+RT and Cr+CHO groups. Also, the Cr+RT group demonstrated average improvements in strength equal to or greater than the Cr+CHO group. The Cr+RT group also experienced decreased body fat by the end of the study whereas the other two groups had increases in body fat.
An earlier double-blind, randomized, crossover study in 2011 investigated whether taking short-term, low-dose aqueous RT extract prior to taking creatine monohydrate (CrM) influences whole body Cr retention, muscle Cr, or measures of anaerobic sprint performance.23 Ten recreationally trained males took 500 mg RT aqueous extract (Finzelberg; Andernach, Germany) or 500 mg placebo twice a day for five days prior to taking five grams CrM (Creapure®, AlzChem AG; Trostberg, Germany). This was repeated after a six-week washout period. At baseline and on each of the five days of supplementation, urine samples were taken and whole body Cr was estimated from samples. Muscle Cr content was determined by muscle biopsies. Additionally, participants performed two 30-second Wingate anaerobic capacity test before and after supplementation to determine peak power, mean power, and total work. No significant differences were observed between the two groups.
Another poster presentation in 2008 addressed the effect of RT on plasma creatine concentration when combined with CrM.24 Eleven healthy males were given 1000 mg (two 500 mg capsules) of as standardized extract of RT (Finzelberg; Andernach, Germany) or placebo, followed by a single dose of 60 mg/kg body weight CrM (Creapure®, AlzChem AG; Trostberg, Germany). Plasma creatine concentrations were analyzed over two hours following ingestion. The RT group experienced a significant reduction of plasma creatine levels at 60, 90, and 120 minutes compared to placebo. The authors state that RT is comparable to the influence of glucose and protein on plasma concentration, but that further research is needed to investigate the effects of RT on creatine uptake and retention in muscle.
FUTURE OUTLOOK
Both French tarragon and Russian tarragon have been traditionally and widely used for culinary purposes as flavor components of food products and, to some extent, as fragrance components of cosmetic products. New research, particularly since 2004 with the development of proprietary branded Russian tarragon extract ingredients, is causing increased interest and market demand. New Russian tarragon-based products are entering markets as functional foods, dietary supplements, and/or licensed or listed medicinal products depending on the regulatory framework of the country where marketed.
Regarding the economics of Russian tarragon cultivation, a farmer’s ability to invest in specialized machinery is an important factor to consider. Smallholder farmers may need to consider sharing the costs and use of harvest and post-harvest processing equipment (e.g., cutter mowers, loader combines [harvesters], and/or combine harvesters [threshers]) with neighboring farms as well as drying facilities with band (belt) dryers, bin dryers, or deep-bed tray driers. The cost of plantlets grown from seed is about three to five euro cents each while planting stock from cuttings ranges from six to eight euro cents per piece. The yield, depending on the location and length of time after planting, ranges between 120 to 170 decitons (one deciton = 100 kg) fresh weight per hectare, of which 70 to 105 decitons are leaf material. The leaf yield in the second year is higher because more cuts are possible. The dry weight leaf yield falls between 16 to 23 decitons per hectare (1,600 to 2,400 kg) with a reported fresh-to-dry leaf ratio range of 4.6:1 to 6.7:1. A tarragon farmer can expect to spend 200 to 250 labor hours per hectare and a farm gate price for the dried herb between €1.10 to €2.30 per kg.5
—Gayle Engels and Josef Brinckmann
REFERENCES
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21. Bloomer RJ, Canale RE, Pischel I. Effect of an aqueous Russian tarragon extract on glucose tolerance in response to an oral dextrose load in non-diabetic men. Nutrition and Dietary Supplements. 2011;3:43-49.
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