Taxonomic Class

Brassicaceae

Common Trade Names

None known.

Common Forms

Available as juice from the leaves, the whole plant, and tea.

Source

An plant parts of Nasturtium officinale are used for medicinal purposes. A low-growing aquatic that belongs to the mustard family, the plant is native to Europe. It is naturalized in the United States and should not be confused with the garden nasturtium or Indian cress (Tropaeolum majus), a popular annual flower that be

longs to a different plant family.

Chemical Components

Watercress contains gluconasturtiin, the glucosinolate precursor of phenethyl isothiocyanate, benzyl glucosinolate, benzyl isothiocyanate (BITC), vitamins A and C, iron, phosphates, and oils.

Actions

The body converts gluconasturtiin to phenethyl isothiocyanate (PEITC). PEITC is also released when the fresh plant is chewed. The N-acetylcys­teine metabolite of PEITC is detectable in human urine . PEITC and synthetic isothiocyanates acted as inhibitors of the tobacco-specific carcinogen nitrosamine 4-(methylnitrosamino )-1­(3-pyridyl)-1-butanone (NNK) in animal models. PEITC is thought to inhibit the metabolic activation NNK and inhibit lung tumorigenesis . In animals, BITC has demonstrated some ability to inhibit lung tumor formation induced by NNK. Doses of 200 mg/kg in rats did not reduce tumor mass and caused toxic effects .

Other in vitro studies suggest that the chemical components of watercress inhibit histamine release.

Reported Uses

The plant is a popular salad green. It has been used as an anti-inflammatory and antimicrobial, and the juice of the leaves has been used to treat acne, eczema, rashes, and topical infections.

Dosage

A dose of 2 oz of fluidextract (juice) P.O. t.i.d. was used in a human clinical study .

Adverse Reactions

None reported.

Interactions

Acetaminophen: May inhibit acetaminophen’s oxidative metabolism . Avoid administration with watercress.

Contraindications and Precautions

Avoid using watercress in pregnant or breast -feeding patients; effects are not clearly documented in humans.

Special Considerations

• Several cases of fascioliasis of the liver (parasitic fluke infection) have been reported after ingesting wild watercress .
• Advise women to avoid using watercress during pregnancy or when breast-feeding.
• Instruct the patient to carefully wash the fresh herb before use if collecting from the wild to reduce the risk of ingesting waterborne parasites or pathogens.
• Inform the patient using other drugs to use watercress cautiously because interactions with watercress are largely unknown.
• Inform the patient that more safety and efficacy data for watercress are needed.

Points of Interest

• Because it contains vitamin C, watercress was once used to prevent scurvy. The use of watercress in salads has been popular for centuries.

Commentary

Although research has shown watercress compounds to be promising anticancer agents, further research is needed. The role of PEITC as a protective agent in human cancers remains to be established. Watercress has no apparent activity against existing tumors. The fact that few reports of toxicity exist despite the consumption of watercress over a long period indicates that this herb is safe. Recommendations for consumption await additional safety research.