Thymus vulgaris

Botany

Thymus vulgaris is a cultivated ornamental, indigenous from the western Mediterranean to southern Italy (1). It is raised from seed or by root division in spring, and prefers light, chalky soils (2). It is an evergreen sub-shrub with a branched stem growing up to 25cm. It has sessile leaves varying from elliptic to linear or diamond-shaped towards the apex. The flowers have a tube-like calyx and tubular corolla with a three lobed lower lip, and are united in spikes at the top of the branches. The roots are robust, and the fruit consists of a smooth, dark coloured nutlet. The whole plant has an aromatic fragrance (1).

History

The name Thyme was given by the Greeks as a derivative of a word which meant ‘to fumigate’, or from the word thumus, signifying courage. The plant was held in medieval times to be a great source of invigoration, inspiring courage. It was an emblem of activity, bravery and energy, and in the days of chivalry the ladies embroidered a bee hovering over a sprig of Thyme on the scarves they presented their knights (3).

Major Active Constituents

Essential oil (1.0-2.5%) containing monoterpenes including thymol (30-70%), carvacrol (70%), thymol methyl ether (1.5-2.5%) (1,4).
Flavonoids, including methylated flavones; phenolic glycosides, aliphatic alcohols. Biphenyl compounds; phenolic acids, including rosmarinic acid. Four acetophenone glycosides have been isolated from the butonol-soluble fraction of thyme extracts, with weak cytotoxic and antioxidant effects in vitro (4)

Actions

Antimicrobial (1,2,3,4,5,6,7,8,9)
Antispasmodic (1,2,3,4,5,6,7,8,9)
Antioxidant (1,2,4,6,7,8)
Expectorant (2,5,6,9)
Anthelmintic (2,5,7)

Pharmacology

Antimicrobial effects
An aqueous extract of 1:1 thyme dose-dependently inhibited Helicobacter pylori in a growth inhibition test and two urease activity assays in vitro (10). In vitro inhibition of Mycobacterium tuberculosis strains was demonstrated by an acetone extract of thyme (11). Thyme essential oil has been proven in many experiments to be highly antibacterial and antifungal when tested on Gram positive and Gram negative bacteria, fungi and yeasts, due to its thymol and carvacrol content (cited in 8).
Brief exposure to a low concentration of thymol rapidly killed cariogenic and periodontopathogenic bacteria, and demonstrated antibacterial activity against other oral bacteria in vitro. The principal mode of action appears to be membrane perforation, resulting in rapid efflux of intracellular constituents (cited in 1). Thyme oil and thymol decreased the growth of Salmonella typhimurium in vitro, particularly under anaerobic conditions. It is thought that the phenolic compounds of thyme exert antibacterial activity by complexing with the bacterial membrane proteins (12).

Antispasmodic activity
Extracts of dried thyme demonstrated a spasmolytic effect on various isolated smooth muscles in vivo. The relaxing effect of bradykinin was also potentiated (13). Bronchospasmolysis is attributed to the flavonoids thymonin, cirsilineol and 8-methoxycirsilineol, shown to be potent spasmolytics by in vitro experiments on guinea pig trachea (cited in 8). A fluid extract of thyme (67% ethanol; containing 0.072% thymol and 0.005% carvacrol) dose dependently and reversibly antagonised contractions of isolated guinea pig trachea preparations provoked by various agonists including prostaglandin and histamine (14).

Antioxidant activity
Antioxidative effects of thyme oil have been attributed mainly to its phenolic constituents (thymol and carvacrol), which has been determined through various test systems as cited in (8). Thymol produced dose-dependent inhibition of endothelial cell-mediated oxidation of low-density lipoprotein in human endothelial cells in vitro, suggesting that it may have potential benefits for human health (15).

Thymol and carvacrol has been demonstrated to have antioxidant activity through decreased peroxidation of phospholipid liposomes and scavenging of peroxyl radicals in vitro (cited in 1). In another study, the non-polar fraction of thyme was examined for the occurrence of phenolic components and their antioxidant activity. In addition to carvacrol and thymol, p-cymene-2,3-diol (I; 2,3-dihydroxy-4-isopropyl-1-methylbenzene) was isolated for the first time from thyme. This compound exhibited the strongest antioxidant activity which was greater than that of a-tocopherol (16).

Other activity
A study determining the expectorant activity of thyme leaf found that it had an inhibiting effect on the normal transport velocity of isolated ciliated oesophageal epithelium, which suggests a decrease in expectorant activity. However an aqueous extract (tea) was used, rather than a liquid extract, which demonstrates only partial mechanism of expectoration (cited in 1).

Daily oral administration of 3.9 mg of thyme essential oil in rats over 17 months resulted in the maintenance of significantly higher levels of polyunsaturated fatty acids (PUFAs) within the retinal phospholipids. As a consequence, the positive influence of thyme on age-related macular degeneration has been questioned (cited in 1,8).

Clinical Outcome Studies

A double-blind, placebo-controlled, multicentre Phase IV study with 361 outpatients assessed the efficacy and tolerability of a combination of dry extracts of thyme herb and primrose root (in combination) compared to a placebo in patients suffering from acute bronchitis with productive cough. The efficacy of the treatment on acute bronchitis was evaluated by the patient's daily counting of coughing fits during the daytime as well as assessment of acute bronchitis related symptoms and by the investigator.

Primary outcome was the change in frequency of coughing fits during daytime on days 7-9 according to patient's accurate daily recording with a manual counter and documentation in a diary. In the thyme-primrose combination group, a 50% reduction in coughing fits from baseline was reached about 2 days earlier compared to the placebo group. The symptoms of acute bronchitis improved rapidly in both groups, but regression was faster and the responder rates compared to placebo were higher under the treatment of thyme-primrose combination. Oral treatment of acute bronchitis with thyme-primrose combination for about 11 days was superior to placebo in terms of efficacy (17). The dosage regime of this trial is unknown. Similar studies have been carried out by the same research group with thyme in combination with ivy leaves, with similar results (18).

In a randomised, double blind comparative study, 60 patients with productive cough complaints were treated with thyme syrup (3x 10 ml daily) or bromhexane preparation for 5 days. No significant difference between the two groups based on self reported symptom relief; both groups made similar gains (cited in 1,8).

In an open, multicentre study, 154 children aged 2 months to 14 years with bronchial catarrh or bronchitis were treated daily with 15-30 ml of thyme syrup, containing 97.6 mg of thyme fluid extract per ml for a period of 7-14 days; 46 patients did not receive medication. Compared to the start of the treatment an improvement in the intensity of coughing was reported in 93% of patients (cited in 8).

Indications

Bronchitis (1,2,5,6,7,9)
Whooping cough (1,2,3,5,6,9)
Upper respiratory catarrh and inflammation (1,2,3,5,6,9)
GIT disorders - colic, spasm, etc (1,3,5,6,7)
Gargle for laryngitis, tonsillitis (2,3,5,6)
Asthma (1,2,5)
Productive cough (1,5,6)

Contraindications and Cautions

According to the German Commission E monographs there are no contraindications, interactions with other drugs or side effects known (9), and no adverse affects are expected from ingestion of thyme (1,8). Other sources state that the essential oil of thyme is not recommended in pregnancy (4,7,8) and contraindicated in those who are allergic to the Lamiaceae family of plants (4,7).

Other cautions are gastritis, enterocolitis and congestive heart failure (cited in 7).
Thyme may induce enzymes in phase one and two detoxification in the liver – the clinical significance of this is unknown (7).

Posology

2-6 ml of 1:2 liquid extract per day; 5-15 ml of 1:5 tincture per day (1). A 5% infusion can be used as a gargle or mouthwash (1,8).
Infusion: take 50 ml 3 times daily for colds (2).
An infusion made from 1 ounce of dried herb to 1 pint of boiling water, sweetened with sugar or honey, given in doses of 1 or more tablespoons, several times daily (3).
1-2 g of thyme extract taken daily in divided doses (4).
1-2 g herb per 1 cup of tea as needed or 1-2 g fluid extract one to three times daily (9).
Fluid extract (1:1) 1-2 ml up to 3 times daily. Fluid extract (1:2) 15-40 ml per week. Tincture (1:5) 2-6 ml three times daily. Infusion of dried herb: 1-4 g three times daily (7).

References

1. Mills S, Bone K. 2000. The Principles and Practice of Phytotherapy. Edinburgh: Churchill Livingstone

2. Chevallier A. 2001. The Encyclopaedia of Medicinal Plants. Penguin

3. Grieve M. 1931. A Modern Herbal. London: Tiger Books

4. Natural Standard Database [Accessed online 23 September 2008] Available: <http://www.naturalstandard.com.ezproxy.scu.edu.au/naturalstandard/monographinfo.asp?title=Thyme&file=thyme>

5. Hoffman D. 2003. Medical Herbalism. Rochester, Vt: Healing Arts Press

6. Bone K. 2003. A Clinical Guide to Blending Liquid Herbs: herbal formulations for the individual patient. St Louis, Missouri: Churchill Livingstone

7. Braun L, Cohen M. 2005. Herbs and Natural Supplements: an evidence based guide. 2nd ed. Marrickville, NSW: Elsevier

8. Anonymous. 2003. Monographs: the scientific foundation for herbal medicinal products. Exeter, UK: European Scientific Cooperative on Phytotherapy

9. Blumenthal M (ed.) 1998. The German Commission E Monographs. Austin, Texas: American Botanical Council.

10. Tabak M, Armon R, Potasman I, Neeman I. In vitro inhibition of Helicobacter pylori by extracts of thyme. J Appl Bacteriol 1996;80: 667-72

11. Lall N, Meyer JJM. In vitro inhibition of drug-resistant and drug-sensitive strains of Mycobacterium tuberculosis by ethnobotanically selected South African plants. J Ethnopharmacol 1999;66:347-54.

12. Juven BJ, Kanner J, Schved F, Weisslowicz H. Factors that interact with the antibacterial action of thyme essential oil and its active constituents. J Applied Bacteriology 1994; 76(6):626-31.

13. Briseid Jensen K, Dyrud OK. The smooth muscle relaxing effect of thyme (Thymus vulgaris L). Acta Pharmacologica Et Toxicologica 1962;19: 345-55.

14. Meister A, Bernhardt G, Christoffel V, Buschauer A. Antispasmodic activity of Thymus vulgaris extract on the isolated guinea-pig trachea: discrimination between drug and ethanol effects. Planta Medica 1999;65 (6):512-6.

15. Pearson DA, Frankel EN, Aeschbach R, German JB. Inhibition of Endothelial Cell-Mediated Oxidation of Low-Density Lipoprotein by Rosemary and Plant Phenolics J Agric Food Chem 1997;45(3):578-582.

16. Schwarz K, Ernst H, Ternes W. Evaluation of Antioxidative Constituents from Thyme. Journal of the Science of Food and Agriculture. 1999;70(2):217-223.

17. Kemmerich B. Evaluation of efficacy and tolerability of a fixed combination of dry extracts of thyme herb and primrose root in adults suffering from acute bronchitis with productive cough. A prospective, double-blind, placebo-controlled multicentre clinical trial. Arzneimittelforschung. 2007;57(9):607-15.

18. Kemmerich B, Eberhardt R, Stammer H. Efficacy and tolerability of a fluid extract combination of thyme herb and ivy leaves and matched placebo in adults suffering from acute bronchitis with productive cough. A prospective, double-blind, placebo-controlled clinical trial. Arzneimittelforschung. 2006;56(9):652-60.

This monograph was authored in 2008 by Stephanie Dierich, a student in Southern Cross University’s Bachelor of Naturopathy programme, and edited by Nena Aleschewski BNat. While the author and editor have strived to cite published information accurately, Southern Cross University will not be responsible for any inaccuracies that may have occurred.

This information is provided for educational purposes only and does not constitute medical advice. If you wish to use herbal medicine as part of your health care, seek the advice of an appropriately qualified practitioner.