Yellow Dock

Summary and Pharmaceutical Comment

Limited chemical, pharmacological, and toxicity information is available for yellow dock. Documented anthraquinone constituents justify the reputed purgative action. However, there is a lack of robust clinical research assessing the efficacy and safety of yellow dock. Although the purgative effect of yellow dock is reputed to be gentle, the use of unstandardised anthraquinone-containing preparations should be avoided since their pharmacological effect is unpredictable and may cause abdominal cramp and diarrhoea. The use of yellow dock should be avoided during pregnancy and lactation.

Food Use

Yellow dock is not used in foods.

Herbal Use

Yellow dock is stated to possess gentle purgative and cholagogue properties. Traditionally, it has been used for chronic skin disease,

obstructive jaundice, constipation, and specifically for psoriasis with constipation.(G7, G64)

Dosage

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

Dried root 2–4 g as a decoction three times daily.(G7)

Liquid extract 2–4 mL (1 : 1 in 25% alcohol) three times daily.(G7)

Tincture 1–2 mL (1 : 5 in 45% alcohol) three times daily.(G7)

Pharmacological Actions

In vitro and animal studies

None documented for the root. Slight antibacterial activity has been reported for herb extracts, which exhibited activity towards both Gram-positive (Staphylococcus aureus, Mycobacterium smegmatis) and Gram-negative (Escherichia coli, Shigella sonnei, Shigella flexneri) organisms.(4)

Clinical studies

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

Side-effects, Toxicity

Clinical data

No side-effects documented. However, there is a lack of clinical safety and toxicity data for yellow dock and further investigation of these aspects is required.. In view of the documented anthraquinone constituents, side-effects generally associated with laxatives are also applicable to yellow dock. Overuse may cause abdominal cramps and diarrhoea, and prolonged use may lead to intestinal atrophy and hypokalaemia.

Preclinical data

Dermatitis has been reported in livestock following the ingestion of plant material in large quantities.(G51) Oxalic acid is known to

be a toxic plant acid that forms insoluble calcium salts which

cause a disturbance in calcium concentrations and hence affect the blood coagulation mechanism.(G33)

Contra-indications, Warnings

Warnings generally associated with stimulant laxatives are also applicable to yellow dock (see Senna). Therefore, yellow dock should not be taken when there is existing intestinal obstruction, and excessive use should be avoided (see Side-effects, Toxicity).

Drug interactions None documented. However, the potential for preparations of yellow dock to interact with other medicines administered concurrently, particularly those with similar or opposing effects, should be considered. Drug interactions listed for other stimulant laxatives are applicable to yellow dock (see Senna).

Pregnancy and lactation In general, unstandardised stimulant laxatives are not recommended for use during pregnancy. The use of yellow dock should therefore be avoided in favour of a standardised preparation that is recommended for the treatment of constipation during pregnancy. The use of yellow dock by breastfeeding women should also be avoided, since it has been documented that anthraquinones can be secreted into the breast milk (see Senna).

Preparations

Proprietary multi-ingredient preparations

Australia: Colax; Colax; Dermaco; Herbal Cleanse; Trifolium Complex. Canada: Herborex. UK: Skin Eruptions Mixture.

References

1 de Siqueira NCS et al. Hydroxyanthraquinones in Rumex crispus L. (of southern Rio Grande). Rev Cent Cienc Biomed 1977; 5: 69–74.

2 Midiwo JO, Rukunga GM. Distribution of anthraquinone pigments in Rumex species of Kenya. Phytochemistry 1985; 24: 1390–1391.

3Fairbairn JW, El-Muhtadi FJ. Chemotaxonomy of anthraquinones in

Rumex. Phytochemistry 1972; 11: 263–268.

4Miyazawa M, Kameoka H. Constituents of essential oil from Rumex crispus. Yakugaku Zasshi 1983; 32: 45–47.

Summary and Pharmaceutical Comment

Limited phytochemical information is available for yucca, steroidal saponins being the only documented constituents. There is limited evidence from clinical studies that a yucca saponin extract has beneficial effects on certain symptoms of arthritis, such as pain and stiffness, and reduces blood pressure and serum triglyceride and cholesterol concentrations. However, robust clinical research assessing the efficacy and safety of yucca is lacking. The traditional use of yucca as a foodstuff would indicate it to be of low toxicity. However there is a lack of information on the safety of medicinal use of yucca. In view of this excessive use of yucca and use during pregnancy and lactation should be avoided.

Species (Family)

Various Yucca species (Asparagaceae) including *Yucca schidigera Roezl ex Ortgies

†Yucca brevifolia Engelm. Yucca glauca Nutt.

Synonym(s)

*Mohave Yucca, Yucca mohavensis Sarg.

†Joshua Tree, Yucca arborescens Trel.

Part(s) Used

Whole plant

Pharmacopoeial and Other Monographs

Martindale 35th edition(G85)

Legal Category (Licensed Products)

Yucca is not listed in the GSL.

Constituents

Terpenoids Various saponins have been isolated from different Yucca species, including tigogenin and chlerogenin,(1) sarsasapogenin, markogenin, higogenin, neo-tigogenin, neo-gitogenin, hecogenin, gloriogenin, and diosgenin (trace)(2) and smilagenin.

Food Use

The yucca plant has been used traditionally as a major foodstuff

by Indian tribes. Previously, in the USA, both Y. schidigera and Y. brevifolia have been approved for food use.(G41)

YHerbal Use

Yucca has been used for the treatment of arthritis, diabetes and stomach disorders. Concentrated plant juice has been used topically to soothe painful joints.

Dosage

None documented.

Pharmacological Actions

In vitro and animal studies

Yucca saponin extract, from Y. schidigera, is reported to exhibit approximately half the haemolytic activity of commercial soap bark saponin.

Antitumour activity against B16 melanoma has been documented for a polysaccharide-containing extract of Y. glauca.(3) The extract was found to be inactive towards L1210 or P388 leukaemias.

Clinical studies

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

A saponin-containing yucca extract has been reported to reduce symptoms of swelling, pain and stiffness in approximately 75 of 150 arthritic patients given the extract in a double-blind study.(4) The onset of a positive response was found to vary from days to weeks or months. A saponin-containing yucca extract has also been documented to reduce blood pressure, abnormal triglyceride, and high cholesterol concentrations in a double-blind study involving 212 arthritic and hypertensive patients.(5) Optimum results were obtained in conjunction with diet and exercise. Yucca extracts have also been reported to provide relief from headaches and to improve circulation and gastrointestinal function.(4, 5)

Side-effects, Toxicity

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

Figure 1 Selected constituents of yucca.

A saponin-containing yucca extract was given to more than 700 arthritic patients with no signs of toxicity documented.(4) The yucca saponins are regarded to be a safe food supplement since they are not thought to be absorbed from the gastrointestinal tract, thereby reducing the dangers of systemic haemolytic activity.(4)

Contra-indications, Warnings

Drug interactions None documented. However, the potential for preparations of yucca to interact with other medicines administered concurrently, particularly those with similar or opposing effects, should be considered.

Pregnancy and lactation In view of the lack of information on the constituents, pharmacology and toxicology of yucca, its use during pregnancy and lactation should be avoided.

Yucca 611

Preparations

Proprietary multi-ingredient preparations

Australia: Prost-1. Brazil: Bronquiogem.

References

1Dewidar AM, El-Munajjed D. The steroid sapogenin constituents of

Agave americana, A. variegata and Yucca gloriosa. Planta Med 1970;

19: 87–91.

2Stohs SJ et al. Steroidal sapogenins of Yucca glauca seeds. Lloydia 1973; 36: 443.

3Ali MS et al. Isolation of antitumor polysaccharide fractions from Yucca glauca Nutt. (Liliaceae). Growth 1978; 42: 213–223.

4 Bingham R et al. Yucca plant saponin in the management of arthritis. J Appl Nutr 1975; 27: 45–51.

5Bingham R et al. Yucca plant saponin in the treatment of hypertension and hypercholesterolemia. J Appl Nutr 1978; 30: 127–136.