Horehound

Scientific Name(s): Marrubium vulgare (Tourn.) L. Family: Laminaceae (mints)

Common Name(s): Horehound , hoarhound , white horehound

Uses

Horehound has been used as a flavoring, expectorant, vasodilator, diaphoretic, diuretic and treatment for intestinal parasites. It reportedly has hypoglycemic effects and influences bile secretion.

Dosing

Horehound is given for digestive complaints as a crude herb at a daily dose of 4.5 g and as a pressed juice of the herb at 30 to 60 mL. 1

Contraindications

Contraindications have not yet been identified.

Pregnancy/Lactation

Information regarding safety and efficacy in pregnancy and lactation is lacking. Avoid use. 2 , 3 , 4 Horehound has emmenagogue and abortifacient effects.

Interactions

None well documented.

Adverse Reactions

Large doses may induce cardiac irregularities.

Toxicology

Marrubiin has an LD 50 of 370 mg/kg when administered orally to rats.

Botany

Horehound is native to Europe and Asia and has been naturalized to other areas, including the United States. 5 It is a perennial aromatic herb of the mint family. The plant grows to a height of about three feet and has oval leaves covered with white, woolly hairs. Horehound bears small, white flowers in dense whorls which bloom from June to August.

History

The leaves and flower tops of the horehound have long been used in home remedies as a bitter tonic for the common cold. They are now used primarily as flavorings in liqueurs, candies and cough drops. In addition, extracts of the plant had been used for the treatment of intestinal parasites and as a diaphoretic and diuretic. A different genus, the black horehound ( Ballota nigra ), is a fetid-odored perennial native to the Mediterranean area that is sometimes used as an adulterant of white horehound.

Chemistry

The bitter principle of horehound is the volatile oil marrubiin, a diterpene lactone. Marrubiin may be an artifact, generated from premarrubiin during isolation. In addition to marrubiin, horehound contains a sterol in an esterified form that is related to compounds found in other plants of the Laminaceae family, and a sesquiterpene that has two nonconjugated double bonds and can be isolated from the nonsaponifiable fraction of extracts. 6

At least six flavonoids have been isolated from the herb: Apigerin, luteolin, apigerin 7-glycoside, luteolin 7-glycoside, quercetin 3-glycoside and quercetin 3-rhamnoglycoside. Two crystalline precipitates from horehound have been found to contain four additional unidentified flavonoids. 7 Horehound contains normal alkanes and four types of branched alkanes: 2- methylalkanes, 3-methylalkanes, 2-(omega-1)-dimethylalkanes and 3-(omega-9)-dimethylalkanes. These molecules are in the C27-C33 series, with odd-numbered chains predominant. Two- and 3-methylalkanes are present in approximately equal proportions in short-chain compounds. 8

In a related species, Marrubium alysson , five known glycosides: verbascoside, leucoseptoside A, martynoside, forsythoside B, leucosceptoside B and a new phenylpropanoid glycoside, alyssonoside, were isolated. 9

Further constituents of horehound are essential oil made up of 0.06% mono and sesquiterpenes, 2.6% to 2.9% tannic acid, resinous substances (eg, ursolic acid), sterols (eg, beta-sitosterol), mucilaginous materials, bitter glycosides and pure marrubina (1,2,5-trimethylnaftalene). 10

Uses and Pharmacology

Expectorant

Horehound has been used traditionally as an expectorant and continues to find a place in cough lozenges and cold preparations.

Animal data

Research reveals no animal data regarding the use of horehound as an expectorant.

Clinical data

The volatile oil has been reported to have expectorant and vasodilatory effects. Similarly, marrubiin stimulates secretion by the bronchial mucosa. 11

Bile stimulation

A study in rats tested the hypothesis that marrubiin stimulates bile secretion. There was no evidence of this, but marrubiin acid, produced by saponification of marrubiin, and the sodium salt of marrubiin acid did stimulate bile secretion. This effect was temporary. 12

Clinical data

Research reveals no clinical data regarding the use of horehound for bile stimulation.

Other uses

In a recent study using rabbits, Marribium vulgare was found to have hypoglycemic effects. 13 This may be important for possible use as an antidiabetic agent. Aqueous extracts of horehound are said to be serotonin-antagonists in vitro. 14

Dosage

Horehound is given for digestive complaints as a crude herb at a daily dose of 4.5 g and as a pressed juice of the herb at 30 to 60 mL. 1

Pregnancy/Lactation

Information regarding safety and efficacy in pregnancy and lactation is lacking. Avoid use. 2 , 3 , 4 Horehound has emmenagogue and abortifacient effects.

Interactions

None well documented.

Adverse Reactions

While marrubiin has been reported to have antiarrhythmic properties, it may also induce cardiac irregularities in larger doses.

Toxicology

Marrubiin has an LD 50 of 370 mg/kg when administered orally to rats. 12

Bibliography

1. Blumenthal M, Brinckmann J, Goldberg A, eds. Herbal Medicine: Expanded Commission E Monographs . Newton, MA: Integrative Medicine Communications; 2000: 197-200.
2. Brinker FJ. Herb Contraindications and Drug interactions . 2nd ed. Sandy, OR: Eclectic Medical Publications; 1998.
3. Newall CA, Anderson LA, Phillipson JD, eds. Herbal Medicines: A Guide for Health-Care Professionals . London: Pharmaceutical Press; 1996.
4. Ernst E. Herbal medicinal products during pregnancy: are they safe? BJOG . 2002;109:227-235.
5. Windholz M, ed. Merck Index, ed 10. Rahway, NJ: Merck and Co., 1983.
6. Nicholas H. Isolation of Marrubiin, a Sterol, and a Sesquiterpene from Marrubium vulgare . J Pharm Sci 1964;53:895.
7. Kowalewska Z, et al. Herba Polonica 1978;24:183.
8. Brieskem CI, et al. Phytochem 1968;7:485.
9. Calis I, et al. Phenylpropanoid Glycosides from Marrubium alysson . Phytochem 1992:31(10):3624.
10. Bartarelli M. [Il Marrubium vulgare e le sue applicazioni farmaceutiche. Parte I.] [Italian] Boll Chim Farm 1966:105(11):787.
11. Tyler VE. The New Honest Herbal. Philadelphia: GF Stickley, 1987.
12. Krejci I, et al. Planta Med 1959;7:1.
13. Cahen R. Pharmacological Spectrum of Marrubium vulgare . CR Soc Biol . 1970;164(7):1467.
14. Cahen R. Pharmacological Spectrum of Planta Med 1959;7:1.

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