Scientific Name(s): Yucca spp.
Common Name(s): Adam's needle, Joshua tree, Mohave yucca, Our Lord's candle, Soapweed yucca, Spanish bayonet, Yucca
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 Y. schidigera (Mohave yucca), Yucca glauca (soapweed yucca), Yucca elephantipes or Yucca gigantea (spineless 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. The dense, terminal flowerhead (panicle) faintly resembles a candle. The flowers are white or greenish. All yucca plants depend on pollination from nocturnal yucca moths (Tegeticula yucca sella), with each variety of moth adapted to a single species of yucca.Leung 1980, Tyler 1992, Yucca 2012
For centuries, yucca plants have been used by indigenous people for a variety of purposes. Traditional uses include boiling and baking the fruits, eating the blossoms, chewing the raw leaves, and fermenting the fruits to produce a beverage for use in rituals. Yucca fiber has been used in making rope, sandals, and cloth. Yucca contains saponins that have a long-lasting soaping action; the roots have been used in soaps and shampoos. Yucca has also been used as a food supplement. The plant is 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 yucca plant. Yucca extracts are currently used commercially as foaming agents in carbonated beverages, as flavorings, and in drug synthesis research.Leung 1980, Tyler 1992
The roots and flowers of yucca are rich in saponin steroidal glycosides consisting of a sapogenin and one or more sugars. Saponins are characterized by their bitter taste and ability to foam when shaken with water. Most species contain sarsasapogenin, tigogenin, furostanol, and spirostanol.Dewidar 1970, Evans 1989, Favel 2005, Kemertelidze 2009, Leung 1980, Piacente 2004, Piacente 2005, Skhirtladze 2006 Y. aloifolia leaves contain up to 1.4% tigogenin, a compound that can be used in the commercial synthesis of steroidal hormones. Numerous phenolic compounds (novel yuccaols and gloriosaols) and spirostane aglycones have been found in yucca species.Cheeke 2006, Nakashima 2016, Nigro 2007, Piacente 2005, Wenzig 2008 Interest has centered on identification of tetrahydroxymethoxystilbene and reservatrol, a phytoalexin with antioxidant properties also found in the skin of grapes, mulberries, and peanuts.Piacente 2004, Piacente 2005 Liquid chromatographic techniques for the identification of phenolic content have been described.Montoro 2008
Uses and Pharmacology
In a study of diabetic rats, Y. schidigera reduced glucose levels, increased insulin levels, improved high-density lipoprotein cholesterol levels, and exerted antioxidant effects.Fidan 2008
In vitro data
Earlier studies attributed anti-inflammatory activity to the saponin content of the plant.Cheeke 2006 Antioxidant activity of the phenols in yucca may also be responsible for an anti-inflammatory effect; studies demonstrate that phenols inhibit inducible nitric oxide synthetase, as well as influence arachidonate metabolism and inhibit cyclo-oxygenase 1 (COX-1) and COX-2 enzymes.Cheeke 2006, Wenzig 2008
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 the use of yucca as an anti-inflammatory agent.Bennett 1977, Cheeke 2006, Williams 2008
Studies evaluating the anti-inflammatory effects of yucca extracts have demonstrated 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.Bennett 1977, Cheeke 2006
Animal/In vitro data
Yucca leaf protein has been found to inhibit herpes simplex virus types 1 and 2 and human cytomegalovirus.Zhang 2008 Steroidal saponin glycosides from the stems, leaves, and flowers of Yucca gloriosa and related species have demonstrated antifungal activity against a number of human pathogens in vitro.Favel 2005, Hayashi 1992, Kemertelidze 2009 One in vitro study demonstrated that yucca saponin-rich extracts had some antibacterial activity against Staphylococcus aureus; however, no antibacterial activity occurred against Salmonella typhimurium and Escherichia coli. Hemolytic activity was also not noted with yucca extracts.Hassan 2010
In a study of gerbils, the butanol extract of Yucca baccata exerted antigiardial activity against Giardia duodenalis trophozoites. Specifically, trophozoite counts were reduced in the duodenum, with a high concentration extract (24.4 mg/mL) producing a reduction in trophozoite count in the proximal segment similar to that noted with metronidazole.Quihui-Cota 2014
In mice, a petroleum ether extract of Y. schidigera attenuated some of the negative effects of a high-fat diet on hormones associated with obesity, such as leptin, ghrelin, insulin, and adiponectin.Kucukkurt 2016
Animal/In vitro data
In vitro antioxidant activity has been evaluated for extracts of whole plant yucca, as well as for phenolic and stilbene constituents.Bassarello 2007, Olas 2008a, Piacente 2004, Piacente 2005 Free radical scavenging assays and other techniques have demonstrated antioxidant activity greater than the reference quercetin.Piacente 2005 Inhibition of lipid peroxidation and nitrogen oxygen generation has been demonstrated.Bassarello 2007, Olas 2008a, Piacente 2004, Piacente 2005 In rats fed yucca extract, a protective effect against nitrate-induced oxidative stress was observed. Decreases in methemoglobin and tissue nitric oxide levels, as well as increases in glutathione and positive histological findings, also occurred.Cigerci 2009 In a murine model, Y. schidigera supplementation reversed arsenic-induced oxidative stress, lipid peroxidation, and superoxide dismutase and catalase activity in a dose-dependent manner.Ince 2013
In vitro data
Reservatrol and yuccaols reduced thrombin-induced platelet aggregation in vitro.Olas 2005, Wenzig 2008 The bark of Y. schidigera caused reductions in platelet adhesion to collagen, aggregation induced by thrombin, and generation of superoxide anion radicals in platelets.Olas 2008b
Animal/In vitro data
Reservatrol-derived gloriosaols have shown antiproliferative and apoptotic-inducing activity in solid tumor and leukemia cell lines.Nigro 2007 Aqueous alcoholic extracts of Y. 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.Ali 1978 In another study involving Y. glauca, steroid glycosides exerted cytotoxic effects against HL-60 (human leukemia) and A549 (human lung adenocarcinoma) cell lines. Additionally, apoptotic effects were exerted against the HL-60 cell line.Yokosuka 2014 Yuccaols isolated from Y. schidigera inhibited vascular endothelial growth factor–induced proliferation and platelet-activating factor biosynthesis in Kaposi sarcoma cells.Balestrieri 2006
In a study of rabbits, yucca powder extract increased conception and kindling rates, with no impact on offspring. Upon examining ovarian fragments, yucca was associated with promoting the release of progesterone but not testosterone or estradiol.Stochmalova 2015 Another study in rabbits showed similar findings.Foldesiova 2017
Whole yucca plant powder is available in tablet form; however, there are no clinical trials upon which to base dosing recommendations.Cheeke 2006
Pregnancy / Lactation
Avoid use. Information regarding safety and efficacy in pregnancy and lactation is lacking.
None well documented.
Information is limited. Yucca powder and yucca extract derived from Y. schidigera have been given GRAS status by the FDA.Olas 2008a, Piacente 2005 Ornamental use of yucca plants is associated with a high incidence of allergic rhinitis.Aydin 2014, Mahillon 2006 A case report describes contact urticaria and sensitization to Y. gigantea. Paulsen 2014
Limited data regarding toxicity of yucca saponins, and the effect of long-term ingestion is available. Saponins are generally considered to be poisonous to lower forms of life, but are nearly nontoxic to humans when taken orally. However, injection of saponins into the bloodstream causes hemolysis, even at extreme dilutions.Leung 1980 A 12-week feeding study in rats found Mohave yucca extract to be essentially nontoxic.Oser 1966 However, in studies evaluating the hepatotoxicity and nephrotoxicity of steroidal saponins in sheep, major adverse renal effects occurred, including tubular necrosis and hemorrhage, with increases in serum creatinine and urea. Upon histological examination, biliary crystals attributed to unhydrolyzed saponins were found in the liver and bile ducts.Wisloff 2008
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