''Quillaja saponaria'', the soap bark tree or soapbark, is an evergreen
tree in the family
Quillajaceae
Quillajaceae is a family of flowering plants. It contains only two extant species, '' Quillaja brasiliensis'' and ''Quillaja saponaria
''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
A leaf (plural, : leaves) is any of the principal appendages of a vascular plant plant stem, stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", wh ...
3–5 cm long; white star-shaped
flowers 15 mm diameter borne in dense
corymbs; and a dry
fruit with five follicles each containing 10–20
seeds.
Characteristics
The inner bark of ''Quillaja saponaria'' can be reduced to powder and employed as a substitute for
soap, since it forms a lather with water, owing to the presence of a
glycoside saponin
Saponins (Latin "sapon", soap + "-in", one of), also selectively referred to as triterpene glycosides, are bitter-tasting usually toxic plant-derived organic chemicals that have a foamy quality when agitated in water. They are widely distributed ...
, sometimes distinguished as
quillaia saponin. It's also applied as an agricultural spray adjuvant. The same, or a closely similar substance, is found in soapwort (''
Saponaria officinalis''), in senega root (''
Polygala senega'') and in
sarsaparilla; it appears to be chemically related to
digitonin, which occurs in ''
digitalis''. The wood is used in cabinetry, and scents derived from the tree are used in perfumes and cosmetics.
Uses
Soap bark tree has a long history of medicinal use with the
Andean people who used it as a treatment for various chest problems. It is the source of
quillaia, the extract of which is used as a
food additive
Food additives are substances added to food to preserve flavor or enhance taste, appearance, or other sensory qualities. Some additives have been used for centuries as part of an effort to preserve food, for example vinegar (pickling), salt (salt ...
and as an ingredient in
pharmaceuticals, personal care products, and fire-fighting foam. It is used as an additive in photographic films and as a
foaming agent for drinks. 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.
QS21 adjuvant is a saponin obtainable from ''Quillaja saponaria'' extract. The
Novavax vaccine for
COVID-19 uses this adjuvant, the
zoster vaccine ''Shingrix'' also contains QS21.
Habitat

This tree occurs at altitudes 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''.
[C. Michael Hogan. 2008] It is often used for
reforestation on
arid soils. It has been introduced as an ornamental in
California. Trees have been acclimatized in
Spain but are rarely cultivated there.
Etymology
''Quillaja'' is derived from the Chilean vernacular name for this species, ''culay''.
[Gledhill, David (2008). "The Names of Plants". Cambridge University Press. (hardback), (paperback). pp 324, 340]
''Saponaria'' means 'soap-like'.
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
Adriana Elisabeth Hoffmann Jacoby (29 January 1940 – 20 March 2022) was a Chilean botanist, environmentalist and author. She was executive secretary of Chile's National Environment Commission (, CONAMA) from 2000 to 2001. She advocated for th ...
. 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.
External links
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{{Taxonbar, from=Q2382775
Chilean Matorral
Flora of central Chile
Trees of Chile
Trees of Mediterranean climate
Drought-tolerant trees
Medicinal plants
saponaria
Saponaceous plants