Scientific Name(s): Yucca spp. Family: Agavaceae
Common Name(s): Yucca , Spanish bayonet , Our Lord's candle , Joshua tree , Adam's needle , Mohave yucca
Yucca has been used historically as a fiber, a soap, and a traditional remedy. In vitro experiments suggest that yucca constituents may exert anti-inflammatory, antifungal, antioxidant, antiplatelet, and antiproliferative activity. Clinical trials are lacking.
Whole yucca plant powder is available in tablet form; however, there are no clinical trials upon which to base dosing recommendations.
Contraindications have not been determined.
Information regarding safety and efficacy in pregnancy and lactation is lacking.
None well documented.
Information is limited. Yucca powder and yucca extract derived from Yucca schidigera possess US Food and Drug Administration GRAS (generally recognized as safe) status. Ornamental use of yucca plants is associated with a high frequency of allergic rhinitis.
Information is limited.
The name yucca applies to as many as 40 species of trees and shrubs found mostly in arid portions of North and Central America. The common names can apply to different species: Spanish bayonet refers to Yucca aloifolia , and Our Lord's candle refers to Yucca whipplei . Other common yuccas include Yucca schidigera (Mohave yucca) and Yucca brevifolia (Joshua tree), which grows to 20 m in height and is commonly found at the bases of desert mountains. Yucca plants are characterized by stiff, evergreen, sword-shaped leaves crowded on a stout trunk. They have a dense, terminal flowerhead (panicle) faintly resembling a candle. The flowers are white or greenish. All yucca plants depend on pollination from nocturnal yucca moths ( Tegeticula yucca sella ). Each variety of moth is adapted to a single species of yucca. 1 , 2 , 3
Yucca plants have served indigenous people for centuries for a variety of uses, including fiber for rope, sandals, and cloth; the roots have been used in soap. Traditional uses also include boiling and baking the fruits, eating the blossoms, chewing the raw leaves, and fermenting the fruits to produce a beverage for rituals. More recently, yucca has been used in soaps, shampoos, and food supplements. Yuccas contain saponins that have a long-lasting soaping action. The plant has been purported to be beneficial for treating hypertension, arthritis, migraine headaches, and colitis, as well as a variety of other disorders. A solid extract is derived from the leaves; the Mohave yucca is the most common commercially used plant. Yucca extracts are currently used commercially as foaming agents in carbonated beverages, as flavorings, and in drug synthesis research. 2 , 3
The roots and flowers of the yucca are rich in saponin steroidal glycosides consisting of a sapogenin and 1 or more sugars. Saponins are characterized by their bitter taste and their ability to foam when shaken with water. Most species contain sarsasapogenin, tigogenin, furostanol, and spirostanol. 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 Y. aloifolia leaves contain up to 1.4% tigogenin, a compound that can be used in the commercial synthesis of steroidal hormones. Phenolic compounds (novel yuccaols and gloriosaols) and spirostane aglycones are numerous in yucca species. 7 , 11 , 12 , 13 Interest has centered on identification of tetrahydroxymethoxystilbene and reservatrol, a phytoalexin with antioxidant properties also found in the skin of grapes, mulberries, and peanuts. 6 , 7 Liquid chromatographic techniques for the identification of phenolic content have been described. 14
Uses and PharmacologyAnti-inflammatory action
Earlier studies attributed anti-inflammatory activity to the saponin content of the plant. 12 Antioxidant activity of the phenols in yucca may also be responsible for an anti-inflammatory effect because they inhibit inducible nitric oxide synthetase (iNOS), as well as influence arachidonate metabolism and inhibit COX-1 and COX-2 enzymes. 11 , 12
Despite the addition of yucca extracts to equine joint supplement preparations and their use in human arthritis treatment based on a few poor-quality studies from the 1970s, no clinical trials exist to support this use. 12 , 15 , 16Antimicrobial activity
Yucca leaf protein has been found to inhibit herpes simplex virus types 1 and 2 and human cytomegalovirus. 17 Steroidal saponin glycosides from the stems, leaves, and flowers of Yucca gloriosa and related species have demonstrated antifungal effects against a number of human pathogens in vitro. 9 , 10 , 18Antioxidant activity
In vitro antioxidant activity has been evaluated for extracts of whole plant yucca as well as for phenolic and stilbene constituents. 6 , 7 , 19 , 20 Free radical scavenging assays and other techniques have demonstrated antioxidant activity greater than the reference quercetin. 7 Inhibition of lipid peroxidation and nitrogen oxygen generation has been demonstrated. 6 , 7 , 19 , 20 In rats fed yucca extract, a protective effect against nitrate-induced oxidative stress was observed. A decrease in methemoglobin and tissue nitric oxide levels, as well as increases in glutathione and positive histological findings, were shown. 21Antiplatelet action
Reservatrol-derived gloriosaols have shown anti-proliferative and apoptotic-inducing activity in solid tumor and leukemia cell lines. 13 Aqueous alcoholic extracts of Yucca glauca flowers have exhibited antitumor activity against B16 melanoma in mice. Analysis of these extracts has identified 2 galactose-containing polysaccharides effective against B16 melanoma but ineffective against L1210 and P388 leukemias in mice. 23Other
A study evaluating the anti-inflammatory effect of yucca extracts observed reductions in blood pressure and serum cholesterol levels, and a reduction in the incidence of migraine headaches from baseline, although the study was not powered to evaluate such effects. 12 , 16
Whole yucca plant powder is available in tablet form; however, there are no clinical trials to determine dosing recommendations. 12
Information regarding safety and efficacy in pregnancy and lactation is lacking.
None well documented. No clinical implication of antiplatelet action of reservatrol has been described.
Information is limited. Yucca powder and yucca extract derived from Y. schidigera have been given GRAS status by the FDA. 7 , 20 Ornamental use of yucca plants is associated with a high incidence of allergic rhinitis. 24
Little is known about the toxicity of yucca saponins, and the effect of long-term ingestion is not well defined. Saponins are generally considered to be poisonous to lower forms of life, but are nearly nontoxic to humans when taken orally. However, their injection into the bloodstream causes hemolysis, even at extreme dilutions. 3 A 12-week feeding study in rats found Mohave yucca extract to be essentially nontoxic. 25 Studies evaluating the hepatoxicity and nephrotoxicity of steroidal saponins in sheep found major adverse renal effects, including tubular necrosis and hemorrhage, with increases in serum creatinine and urea. On histological examination, biliary crystals attributed to unhydrolyzed saponins were found in the liver and bile ducts. 26
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