Chemical constituents and active ingredients of pau d'arco

Pau d'arco contains anthraquinones, naphthoquinones, furano-naphthoquinones, derivatives of benzoic acid, iridoid glycosides1, alkaloids, dehydro-alpha-lapachone, dehydroisolapachone, catechins, steroids, simple phenols, flavones, flavonols, flavanones, cyanogenic heterosides, saponines, triterpenes, xanthines, β-sitosterol, β-carotene, chrysophanic acid, ascorbic acid, niacin, riboflavin, tiamin, several macro and microelements (Cr, Mn, P, Mg, Fe, Zn, Si, K, Sn, Ca) and resin.2

Lapachol is the constituent which has attracted the greatest interest. It is present in the bark, together with dehydroiso-α-lapachone and dehydro-α-lapachone1. Lapachol has been known since 1858 r, being the first natural substance isolated from the lapacho tree (Tabebuia impetiginosa). Tabebuia wood also contains lapachone isomers: α-lapachone i β-lapachone3. Lapachol is a yellow crystalline dye which changes its color to red in an alkaline environment and is responsible for the yellow color of the plant. It is poorly soluble even in hot water5. The wood of the plant has 2-7% lapachol and its derivatives. The bark contains less lapachol than the wood.6

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References:

1. 1. van Wyk B.E., Wink M. (2008) Rośliny lecznicze świata, MedPharm, Wrocław. ISBN 978-83-60466-51-3
2. 2. Żurowska K. (2001) Ziołolecznictwo amazońskie i andyjskie, Tower Press, Gdańsk. ISBN 83-87342-41-6
3. 3. Gómez Castellanos JR, Prieto JM, Heinrich M. (2009) Red Lapacho (Tabebuia impetiginosa)--a global ethnopharmacological commodity? J Ethnopharmacol 121, 1-13.
4. 4. Węglarska J., Węglarski K. (2008) Użyteczne rośliny tropików Szkice etnobotaniczne, Bogucki Wydawnictwo Naukowe, Poznań.
5. 5. Mills S., Bone K. (2005) The Essential Guide to Herbal Safety. Elsevier Churchill Livingstone, St. Louis. ISBN 0443071713, 9780443071713
6. 6. Fugh-Berman A. (2003) The 5-Minute Herb and Dietary Supplement Consult. Lippincott Williams & Wilkins, Hagerstwon. ISBN 0683302736, 9780683302738