Corn Silk

Summary and Pharmaceutical Comment

Limited information is available on the constituents of corn silk. Extracts have been reported to exhibit diuretic actions in both humans and animals, thus justifying the reputed herbal uses. However, no additional data were located to support these reported actions. In view of the lack of toxicity data, excessive use of corn silk should be avoided.

Species (Family)

Zea mays L. (Gramineae)

Synonym(s)

Stigma Maydis, Maize, Zea

Part(s) Used

Stigma, style

Pharmacopoeial and Other Monographs

BHC 1992(G6)

BHP 1996(G9)

Martindale 35th edition(G85)

Legal Category (Licensed Products)

Corn silk is not included in the GSL.(G37)

Constituents

The following is compiled from several sources, including General References G2 and G6.

Amines 0.05%. Type not specified, although hordenine is listed for the genus Zea.

Fixed oils 1.85–2.25%. Contain glycerides of linoleic, oleic, palmitic and stearic acids.

Saponins 3% (unspecified).

Tannins Up to 11.5–13% (unspecified).

Other constituents Allantoin, bitter glycosides (1%), cryptoxanthin, cyanogenetic compound (unidentified),(1) flavone (maysin), gum, phytosterols (e.g. sitosterol, stigmasterol), pigments, resin, vitamins (C and K).

Figure 1 Selected constituents of corn silk.

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Food Use

Corn silk is listed as a natural source of food flavouring (category N2). This category indicates that corn silk can be added to foodstuffs in small quantities, with a possible limitation of an active principle (as yet unspecified) in the final product. Previously, corn silk has been listed as GRAS (Generally

Recognised As Safe).(G41) The fruits are classified as category N1 with no restriction on their use.(G16) Corn (maize) oil and

flour are commonly used in cooking.

Herbal Use

Corn silk is stated to possess diuretic and stone-reducing properties. It has been used for cystitis, urethritis, nocturnal

enuresis, prostatitis, and specifically for acute or chronic inflammation of the urinary system.(G2, G6, G7, G8, G64)

Dosage

Dosages for oral administration (adults) for traditional uses recommended in standard herbal reference texts are given below.

Dried style/stigma 4–8 g as an infusion three times daily.(G6, G7)

Liquid Extract of Maize Stigmas (BPC 1923) 4–8 mL.

Tincture 5–15 mL (1 : 5 in 25% alcohol) three times daily.(G6, G7)

Figure 2 Corn silk (Zea mays).

192 Corn Silk

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Figure 3 Corn silk – dried drug substance (stigma).

Pharmacological Actions

In vitro and animal studies

Corn silk is stated to possess cholagogue, diuretic, hypoglycaemic, and hypotensive activities in laboratory animals.(2, G41) Utilising aqueous extracts, a methanol-insoluble fraction has been reported to exhibit diuretic activity in rabbits,(G41) and an isolated crystalline component has been documented to have a hypotensive action and to stimulate uterine contraction in rabbits.(3) The latter two actions were thought to involve a cholinergic mechanism. The action of corn silk extract on experimental periodontolysis in hamsters has been documented.(4)

Cryptoxanthin is stated to possess vitamin A activity,(G48) and tannins are known to possess astringent properties.

Clinical studies

There is a lack of clinical research assessing the effects of corn silk and rigorous randomised controlled clinical trials are required.

It has been stated that an aqueous extract is strongly diuretic in humans,(G41) and that clinical studies have indicated corn silk to

be effective in kidney and other diseases.(G41) No further information on human studies was located to support these statements.

Side-effects, Toxicity

There is a lack of clinical safety and toxicity data for corn silk and further investigation of these aspects is required.

Allergic reactions including contact dermatitis and urticaria

have been documented for corn silk, its pollen and for starch derived from corn silk.(G51) Cornstarch is considered to be a

known allergen.(G51) The toxicity of a methanol-insoluble fraction of an aqueous corn silk extract has been reported to be low in rabbits. The effective intravenous dose for a diuretic action was

documented as 1.5 mg/kg body weight compared to the lethal intravenous dose of 250 mg/kg.(G41) Corn silk contains an

unidentified toxic principle,(1, 2) and is listed as being capable of producing a cyanogenetic compound.(1)

Contra-indications, Warnings

Corn silk may cause an allergic reaction in susceptible individuals.

Drug interactions None documented. However, the potential for preparations of corn silk to interact with other medicines administered concurrently, particularly those with similar or opposing effects, should be considered. There is limited evidence from preclinical studies that corn silk has hypoglycaemic and hypotensive activity.

Pregnancy and lactation Corn silk has been documented to stimulate uterine contractions in rabbits. In view of this, doses of corn silk greatly exceeding amounts used in foods should not be taken during pregnancy or lactation.

Preparations

Proprietary single-ingredient preparations

UK: Protat.

Proprietary multi-ingredient preparations

Spain: Diurinat; Renusor. UK: Elixir Damiana and Saw Palmetto; Napiers Uva Ursi Tea; Roberts Black Willow Compound Tablets. USA: Cran Support.

References

1 Seigler DS. Plants of the northeastern United States that produce cyanogenic compounds. Economic Bot 1976; 30: 395–407.

2Bever BO, Zahnd GR. Plants with oral hypoglycaemic action. Q J Crude Drug Res 1979; 17: 139–196.

3Hahn SJ. Pharmacological action of Maydis stigma. K'at'ollik Taehak Uihakpu Nonmunjip 1973; 25: 127–141.

4Chaput A et al. Action of Zea mays L. unsaponifiable titre extract on experimental periodontolysis in hamsters. Med Hyg (Geneve) 1972; 30: 1470–1471.

Summary and Pharmaceutical Comment

Limited chemical data are available for couchgrass and little scientific evidence was located to justify the traditional herbal uses. Agropyrene is regarded as the main active principle in couchgrass on account of its antibiotic effect, although the presence of agropyrene in the volatile oil has been disputed. In view of the lack of toxicity data, excessive ingestion should be avoided.

Species (Family)

Elymus repens (L.) Gould [Elytrigia repens (L.) Desv. Ex Nevski] (Gramineae)

Synonym(s)

Agropyron, Agropyron repens Beauv., Dogs Grass, Quackgrass, Triticum, Triticum repens L., Twitch, Twitchgrass

Part(s) Used

Rhizome

Pharmacopoeial and Other Monographs

BHP 1996(G9)

BP 2007(G84)

Complete German Commission E(G3)

Martindale 35th edition(G85)

Ph Eur 2007(G81)

WHO volume 1 1999(G63)

Legal Category (Licensed Products)

GSL (Agropyron)(G37)

Constituents

The following is compiled from several sources, including General References G2 and G7.

Carbohydrates Fructose, glucose, inositol, mannitol, mucilaginous substances (10%), pectin, triticin.

Cyanogenetic glycosides Unspecified.

Flavonoids Tricin and other unidentified flavonoids.

Saponins No details documented.

Volatile oils 0.05%. Agropyrene (95%). Presence of agropyrene has been disputed,(1) with the oil reported to consist mainly of the monoterpenes carvacrol, trans-anethole, carvone, thymol, menthol, menthone and p-cymene and three sesquiterpenes.

Other constituents Fixed oil, vanillin glucoside.

Food Use

Couchgrass is listed by the Council of Europe as a natural source of food flavouring (category N2). This category indicates that couchgrass can be added to foodstuffs in small quantities, with a

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possible limitation of an active principle (as yet unspecified) in the

final product.(G16) Previously, couchgrass has been listed as GRAS (Generally Recognised As Safe).(G41)

Herbal Use

Couchgrass is stated to possess diuretic properties. It has been used for cystitis, urethritis, prostatitis, benign prostatic hypertrophy, renal calculus, lithuria, and specifically for cystitis with irritation or inflammation of the urinary tract.(G2, G7, G64)

Dosage

Dosages for oral administration (adults) for traditional uses recommended in older and contemporary standard herbal reference texts are given below.

Dried rhizome 4–8 g as an decoction three times daily.(G7)

Liquid extract 4–8 mL (1 : 1 in 25% alcohol) three times daily.(G7)

Tincture 5–15 mL (1 : 5 in 40% alcohol) three times daily.(G7)

Pharmacological Actions

In vitro and animal studies

Couchgrass is stated to exhibit diuretic and sedative activities in rats and mice, respectively.(G41) Broad antibiotic activity has been

documented for agropyrene and its oxidation product.(G41) An ethanolic extract was found to exhibit only weak inhibition (14%) of carrageenan-induced inflammation in the rat paw.(2)

Couchgrass has been reported to be phytotoxic with flavonoid components implicated as the active constituents.(3)

Figure 1 Couchgrass (Elymus repens).

194 Couchgrass

Clinical studies

There is a lack of clinical research assessing the effects of couchgrass and rigorous randomised controlled clinical trials are required.

CSide-effects, Toxicity

None documented. However, there is a lack of clinical safety and toxicity data for couchgrass and further investigation of these aspects is required. An unspecified cyanogenetic glycoside has

been reported as a constituent of couchgrass, although no further details were located.(G7)

Contra-indications, Warnings

Drug interactions None documented. However, the potential for preparations of couchgrass to interact with other medicines administered concurrently, particularly those with similar or opposing effects, should be considered. The clinical relevance of the reputed diuretic action is unclear.

Pregnancy and lactation In view of the limited pharmacological and toxicological data, the use of couchgrass during pregnancy and lactation should be avoided.

Preparations

Proprietary single-ingredient preparations

Germany: Acorus.

Proprietary multi-ingredient preparations

France: Herbesan; Mediflor Tisane Antirhumatismale No 2; Mediflor Tisane No 4 Diuretique; Obeflorine; Tisane Hepatique de Hoerdt. Germany: Hevert-Blasen-Nieren-Tee N; Renob Blasenund Nierentee. Italy: Emmenoiasi; Tisana Kelemata. Spain: Diurinat; Renusor. UK: Antitis; Fenneherb Cystaid; Kas-Bah; Napiers Uva Ursi Tea. USA: Natural Herbal Water Tablets.

References

1Boesel R, Schilcher H. Composition of the essential oil of Agropyrum repens rhizome. Planta Med 1989; 55: 399–400.

2Mascolo N. Biological screening of Italian medicinal plants for antiinflammatory activity. Phytother Res 1987; 1: 28–29.

3Weston LA et al. Isolation, characterization and activity of phytotoxic compounds from quackgrass [Agropyron repens (L.) Beauv.]. J Chem Ecol 1987; 13: 403–421.