Quillaja saponaria, the soap bark tree or soapbark, is an evergreen tree in the family Quillajaceae, native to warm temperate central Chile. In Chile it occurs from 32 to 40° South Latitude approximately and at up to 2000 m (6500 ft) above sea level. It can grow to 15–20 m (50–65 ft) in height. The tree has thick, dark bark; smooth, leathery, shiny, oval evergreen leaves 3–5 cm long; white star-shaped flowers 15 mm in diameter borne in dense corymbs; and a dry fruit with five follicles each containing 10–20 seeds. The tree has several practical and commercial uses.

Habitat

thumb|right|Sclerophyll forests in the [[Santiago Metropolitan Region in Chile]]

This tree occurs at elevations up to 2000 metres. The species is drought resistant, and tolerates about −12 °C (10 °F) in its natural habitat. Examples of specific occurrences are in central Chile in the forests of La Campana National Park and Cerro La Campana, in which locales it is associated with the Chilean wine palm, Jubaea chilensis. It is often used for reforestation on arid soils.

The plant has been introduced as an ornamental in California, and has been acclimatized in Spain but is rarely cultivated there.

Taxonomy

Quillaja saponaria was originally described in 1782 by Juan Ignacio Molina., and the Chilean vernacular name for this species, culay.

Saponaria means 'soap-like'. The saponin content of the bark helps to stimulate the production of a more watery mucus in the airways, thus facilitating the removal of phlegm through coughing.

The saponins of this tree are also considered to have adjuvant properties for vaccine solutions, and have been used for this purpose since 2017. the zoster vaccine Shingrix also contains QS21 as well as the RSV vaccine Arexvy.

Toxicity

First described by Edwin John Quekett, Q. saponaria wood and bark is known to contain raphides, which George Gulliver found were concentrated along the liber and mesophloeum.

References

Sources

  • C. Donoso. 2005. Árboles nativos de Chile. Guía de reconocimiento. Edición 4. Marisa Cuneo Ediciones, Valdivia, Chile. 136p.
  • Encyclopedia of the Chilean Flora. 2009. Quillaja saponaria
  • Adriana Hoffmann. 1998. Flora Silvestre de Chile, Zona Central. Edición 4. Fundación Claudio Gay, Santiago. 254p.
  • C. Michael Hogan. 2008. Chilean Wine Palm: Jubaea chilensis, GlobalTwitcher.com, ed. Nicklas Stromberg
  • J. Taylor. 1990. The Milder Garden. Dent
  • Chevallier, Andrew, 1996. The Encyclopedia of Medicinal Plants, Dorling Kindersley, 336p.
  • Singh, Manmohan, 2007. Vaccine Adjuvants and Delivery Systems, John Wiley & Sons, Hoboken, New Jersey, 457 pp.