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Compilation by Armando Gonzalez Stuart, PhD

Scientific Name:

Eysenhardtia polystachya

Botanical Family:


Other Common Name:

Coate, coahtli, coatillo, coatli, cojtle, sipariqui, urza (Berdonces, 2009; White, 2002; Schoenhals, 1988).

Common names in Spanish:

Palo azul, palo cuate, palo dulce, palo dulce blanco, palo de los riñones, leño nefrítico, Lignum nephriticum, rosilla, taray, taray de México, vara dulce, varaduz (White, 2002; Martínez, 1989).

Where is it found?

This small tree is native to Mexico and Southwestern North America (Berdonces, 2009; Mabberley, 2008).

Parts of the plant used:

The wood, branches, and leaves.

How is it used?

The wood chips and or leafy branches can be steeped or boiled in water to make tea.

When the wood chips are steeped in cold water for a few hours, they confer a blue hue to the water (hence one of its popular names in Spanish, palo azul or “blue stick”). This color can later change to red or amber, according to the incidence of the light. The Spanish physicians first recorded the intense blue fluorescence of kidney wood tea in the sixteenth century. This interesting phenomenon is due to a novel four-ringed chemical compound known as tetrahydromethanobenzofuro[2,3-d]oxacine, which is not found in the intact plant, but rather is the end product of an unusual spontaneous oxidation involving some of the plant’s natural compounds known as flavonoids (Acuña et al., 2009; Berdonces, 2009; Mabberley, 2008; Martínez, 1989).

What is it used for?

This plant has been used medicinally for centuries and was well known to the indigenous peoples of Mexico and parts of Central America well before the European invasion. The Spaniards were the first Europeans to take this plant to their homeland where it quickly became very popular for the treatment of various urinary tract diseases (Martínez, 1989).

In Mexico, the wood is either placed in water and taken as a cold tea or the branches and leaves are decocted (boiled) in water and taken for various health problems. These include urinary infections, to improve urine flow (diuretic), against kidney inflammation (nephritis) and pain, against kidney stones, to lower fevers, to treat stomach problems (colics), and as a general tonic (Jiménez, 2011; Mendoza-Castelán and Lugo-Pérez, 2011; Salinas-Hernández et al., 2008; Martínez, 1989). The tea is added to the water for livestock and poultry to drink in order to prevent disease (Jiménez, 2011; Martínez, 1989). The leaves of a related species, E. texana (Texas kidneywood) are macerated (soaked) in water and the cold tea is drunk to relieve kidney problems (Quattrocchi, 2012).

A study evaluated the in vitro acaricidal (tick-killing) effect of two types of compounds known as coatlines and matlalines, extracted from kidneywood. The results of the study showed that the acaricidal activity of matlalines against both larvae as well as adults was more much more efficient compared to the coatlines. The authors concluded that some of the kidneywood compounds show promise against certain species of cattle ticks, such as Rhipicephalus (Boophilus) microplus, for example (Gutiérrez et al., 2015).

A study by Gutiérrez and Báez (2014) using diabetic mice showed that a kidneywood methanol-water extract possessed considerable antioxidant activity against free radicals or reactive oxygen species (ROS) that cause oxidative stress and inflammation. Additionally, the plant compounds showed anti-glycation, liver -protective and hypoglycemic (lower blood sugar levels) actions that could be potentially beneficial against type 2 diabetes.
An ethnobotanical study of ethanol extracts obtained from various medicinal plants used in the Mexican traditional medicine to treat oral bacterial diseases showed that kidneywood was among those that exhibited the highest in vitro inhibitory effect against the bacterial species Streptococcus mutans and Porphyromonas gingivalis (Rosas-Piñón et al., 2012).

A phytochemical study of kidneywood showed that it possesses antimicrobial, cytotoxic, and insecticidal properties; displaying moderate cytotoxic action against KB cell lines (Álvarez et al., 1998).


Safety / Precautions


  • The safety of using kidneywood during pregnancy and lactation has not been established.

Before you decide to take any medicinal herb or herbal supplement, be sure to consult with your health care professional first. Avoid self-diagnosis and self-medication: Always be on the safe side!



  • Acuña AU et al. Structure and formation of the fluorescent compound of Lignum nephriticum. Org Lett. 2009 ;11(14):3020-3.
  • Alvarez L et al. Cytotoxic isoflavans from Eysenhardtia polystachya.
    J Nat Prod. 1998;61(6):767-70.
  • Berdonces JL. Gran Diccionario de las Plantas Medicinales.
    Barcelona, Spain: Editorial Oceano; 2009; pp. 857-858.
  • Gutierrez L. et al. Ixodicide activity of Eysenhardtia polystachya against Rhipicephalus (Boophilus) microplus. J Anim Sci. 2015;93(4):1980-6.
  • Gutierrez RM, Baez EG. Evaluation of antidiabetic, antioxidant and antiglycating activities of the Eysenhardtia polystachya. Pharmacogn Mag. 2014 ;10(Suppl 2):S404-18.
  • Jiménez A. Herbolaria mexicana 2a ed.
    Madrid: Mundi-Prensa; 2012; p. 356.
  • Mabberley D. Mabberley’s Plant Book 3rd ed.
    London: Cambridge University Press; 2008; p. 331.
  • Martínez M. Plantas Medicinales de México.
    México, D.F.: Editorial Botas; 1989; pp. 469-470.
  • Mendoza-Castelán G, Lugo-Pérez R. Plantas Medicinales en los Mercados de México.
    Chapingo, Estado de México: Universidad Autónoma Chapingo; 2011; pp. 658-659.
  • Quattrocchi, U. World Dictionary of Medicinal and Poisonous Plants, Vol. 3.
    Boca Raton, FL: CRC Press; 2012; p. 206.
  • Schoenhals L. A Spanish-English Glossary of Mexican Flora and Fauna.
    Mexico City: Summer Institute of Linguistics: 1988; p. 144.
  • Rosas-Piñón Y. et al. Ethnobotanical survey and antibacterial activity of plants used in the Altiplane region of Mexico for the treatment of oral cavity infections.
    J Ethnopharmacol. 2012 ;141(3):860-5.
  • Salinas-Hernández P. et al. Development of a capillary electrophoresis method for the characterization of "palo azul" (Eysenhardtia polystachya). J Sep Sci. 2008;31(4):741-5.
  • White R. Elsevier’s Dictionary of Plant Names of North America Including Mexico.
    Amsterdam: Elsevier; 2003; p. 82.