Hi, t_kvale-ga !
Yes, there does seem to be some evidence for the environmental
benefits of soapnut, mostly through its anti-microbial and
anti-bacterial properties. Many of its other properties seem to be
more highly researched. It is the saponins in the plant which are the
important product of the plant, and the soapnut is particularly rich
An well presented and well referenced site is maintained by Professor
C. Kamaswara Rao of the Department of Forests Environment and Ecology
of the Government of Karnataka. It focuses on Indian Medicinal Plants.
It gives a good summary of the properties of saponins and the plants
containing them at:
Discussing the soapnut tree, he states, among other things:
"Saponins are naturally occurring chemical compounds, with the
properties of soaps and detergents. They occur in different tissues of
a large number of plant species including many common Indian food and
medicinal plants. Although predominant in angiosperms, saponins also
occur in some ferns (species of Polypodium and Cyclamen) and possibly
algae. They even occur in some marine animals and snake venom as
Saponins are toxic to a variety of organisms, from bacteria to higher
plants and animals. Populations of aquatic animals such as fish and
molluscs are controlled by using saponin containing plants. Saponins
are also toxic to different degrees to mammals particularly, when
introduced into the circulatory system. Saponins mainly act through
solubilising and destabilising the membrane systems of cells, by
complexing with the steroidal components of the membranes."
So yes, there is evidence for the anti-bacterial properties of the
soap nut, although it is only one plant with these properties. The use
of saponin containing plants to control fish populations is a very
interesting form of environmental balancing.
Professor Rao cites as sources the following studies:
Oakenfull and Sidhu (1989),
Hostettmann et al., (1991),
Sangeetaa and Kameswara Rao (1993
Kameswara Rao and Sangeetaa (1993),
Kameswara Rao and Sangeetaa (1997).
Sharu Raj, 1990;
Sathyanarayana Bhat, 1993;
Shubha Rani, 1995
Note that some of these are studies in which he has himself taken
part. Details of study results can be found in the appendices, and the
whole site is highly professional.
The North East India Databank has a site at:
It tells us that there is more than one kind of soapnut tree:
"Saponin Bearing Plants (Technology Source: RRL-Bhub):
The commonly known soapnut trees, (Sapindus emarginatus and Sapindus
mukorossi) are widely distributed in Karnataka, Andhra Pradesh,
Orissa, Himachal Pradesh and other northern parts of India. The
detergent property in soapnut is due to the presence of triterpene
saponins. The saponin content in soapnuts varies from 10 to 18%. The
saponins are use in detergents, shampoos, textiles, foods,
pharmaceuticals and photo film industry. The photo film industry alone
requires about 6t of saponin per annum, presently being totally
The process has been developed for isolation and purification of
saponins from the soapnuts. The soapnuts are cut and separated into
pericarp and the seeds. The pericarp is used in the saponin."
Sabinsa - of New Jersey and Utah - have a website at:
In their June 2001 newsletter they describe one of their products:
"SapindinTM is Sabinsa's trademark for Soapnut Saponins, a product
prepared from the fruit (nuts) of the Soapnut tree, Sapindus
trifoliatus. The Soapnut tree is a rich source of saponins that
function as a mild cleanser and antimicrobial.21 "
The source cited is:
" 21. Tanaka, O. et al. Application of Saponins in Foods and
Cosmetics: Saponins of Mohave yucca and Sapindus mukurossi. In:
Saponins Used in Food and Agriculture. George R. Waller and Kazuo
Yamasaki eds. Advances in Experimental Medicine and Biology Volume
405, Plenum Press, 1996, pages 1-11. "
Himalaya Health Care describe the soapnut tree and its properties at:
"The fruit is valued for the saponins (10.1 %) present in the pericarp
which constitutes up to 56.5 per cent of the drupe. The fruits are
credited with expectorant and emetic properties and are used in the
treatment of excessive salivation, epilepsy and chlorosis. The
powdered seeds are said to possess insecticide properties. ..... It
cleanses the skin of oily secretion and is even used as a cleanser for
washing hair and a hair tonic, and forms a rich, natural lather...."
Click on the link at the bottom of the description of the plant for a
more detailed monograph, or go to:
This adds the information:
"Saponins are the major active constituent of the fruit pulp.
Mukorosside is one of the saponins isolated from the fruit rind 1 ."
The reference is to "Indian J. Chem. 1966, 4, 36."
More references to the properties of saponins in general can be found
"Saponins are mainly of the triterpenoidal type, being the oleanolic
acid and the hedagenin the main constituents.
SAPONIN CHEMISTRY: Saponins are glycosidic compounds composed of a
steroid (c-27) or triterpenoid (C30) saponin nucleus with one or more
carbohydrate branches. "
Here they claim anti-cancer properties for saponins, citing a study by
Dr. A.V. Rao, professor and researcher in the Department of
Nutritional Science at the University of Toronto, Canada and his
Wildwood Magazine also points to other sources of saponins, such as
Yucca soybeans and quillaja on their page at:
They cite Dr. Rene Malinow as demonstrating that saponins lower
cholesterol by binding to bile acids and cholesterol in the intestine.
(This prevents cholesterol from being reabsorbed in the intestine.)
They also give other references including some which are actually
"Cheeke, Peter R., Ph.D. "Saponins: Surprising benefits of desert
plants." Online Posting. 23 June 1998. 19 July 2001.
Erdman, John W., PhD. Circulation. AHA Science Advisory. Soy Protein
and Cardiovascular Disease: A Statement for Healthcare Professionals
From the Nutrition Committee of the AHA. 2000;102:2555. Copyright 2000
American Heart Association, Inc. Online Posting. 20 July 2001.
Jeon, HS; Sung, MK. Soybean Saponins Inhibit the Formation of DNA
Adducts in Human Colon and Liver Cells. Third International Symposium
on the Role of Soy in Preventing and Treating Chronic Disease. October
31-November 3, 1999. Omni Shoreham Hotel, Washington DC, USA.
Paxton, Suzanne, R.Ph. "Soy Protein: Your Key to Better Health."
Online Posting. March 1998. 18 July 2001. www.soybean.com.
A well referenced article of the benefits of soy products, including
saponin content can be found at:
"Saponins, phytates, and protease inhibitors have been called
antinutients, and were viewed negatively in the past. Now scientists
are finding that they also have benefits. Saponinis are antioxidants,
and thus protect against cell damage. Sappiness was recently shown to
inhibit the growth of colon cancer cells in vitro.23 "
Therre are extensive references in the footnotes (scroll down). From
the spelling errors I assume the article was transcribed from
Lastly, there is supposed to be a pdf file containing a 1988 study
into the pharmacological activities of the triterpine saponins at:
but the link seems to be outdated or broken.
As you can see, apart from Professor Rao's scholarly summary, the
emphasis seems to be on either the cleansing or medicinal properties
of the soapnut, with the additional advantage that if you flush it
down the drain along with your ahmpoo it's not going to harm anything,
and may kill a few germs on the wway. The environmental benefits are
generally seen as a side bonus.
Thank you for an interesting question.
Clarification of Answer by
22 Apr 2003 23:52 PDT
Conducting a search on the words "saponin fish" turned up some
Gih Hwa Enterprises discuss the use of Tea Saponin in aquaculture at:
They claim it is a natural protection agent, and say:
"Tea saponin can prevent the incidence of prawn black gill, control
its parasites and accelerate its exudation and growth. For its
hemolysis and fish-farm function, it is a good natural protective
agent to kill harmful fishes, but no effects on prawn (safe
concentration is 20ppm). Tea saponin has three main effective results.
Eliminate the unwanted fish in the shrimp ponds
Help shrimps take of shell earlier and enhance the growth of shrimps
Automatically decompose into organic fertilizer, which can promote the
growth of algae .......
.......Do NOT apply to fish ponds. "
This is borne out by Quantumwide of Malaysia at:
"... Saponin has been shown to be an effective fish killing agent with
a 40 fold margin of safety towards freshwater and marine
invertebrates, especially prawns and shrimps. The differentia toxicity
of Saponin towards fin-fish in the presence of shrimps makes it an
ideal selective toxicant for the removal of fin-fish in shrimp
So it does not seem to be a good idea to release it into any kind of
A 2002 article by Jeremy St. Onge on "Fish-poison use in the Americas"
can be found at:
He discusses the subject in general and the use of saponins in
"The most common use of fishing poisons documented are plants
containing saponin, a glucoside poison. This chemical is usually
active in the stem or wood and is diversely distributed among several
plant families (Amaryllidaceae, Convolvulaceae, Dioscoreaceae,
Lamiaceae, Lecythidaceae, Liliaceae, Papilionaceae, Sapindaceae,
Scrophulariaceae, Solanaceae, Verbenaceae, and others). Plants
containing saponin are also commonly used as soap substitutes because
they can often be worked into a lather. Likely, saponin plants were
primarily used for washing or cleaning and secondarily used as a
poison after their effect on fish in washing-streams was discovered.
Saponin normally breaks down in the digestive system and must enter
the bloodstream to be toxic (Elpel, 2000), but fish assimilate saponin
directly into their bloodstream via their gills. Fish poisoned by
saponin become stupefied and float to the surface where they can
easily be collected. "
After reviewing the use of these and other fish poisons he concludes,
"...Unfortunately, the poisoning of streams to capture fish has had
ecological consequences. The efficiency of this method has ensured
that its increasing use as populations increase may result in the
extirpation of susceptible fish species from their native streams..."
He cites extensive references including "Pacific Island Ecosystems at
Risk". Internet. http://www.hear.org/pier/deell.htm
Clearly it would not be wise to release commercial quantities into the
storm water system, especially where that debouches into a river or
lake system. There might be less problem releasing it into a sewage
system where the sewage is later treated.
Ironically, a study by Francis, G., Makkar, H. P. S., and Becker,
K.:. of the University of Hohenheim, suggests that Dietary
supplementation with a Quillaja saponin mixture improves growth
performance and metabolic efficiency in common carp:
I am afraid I have found no evidence that saponins are particularly
beneficial directly in water run-offs other than the anti-bacterial
properties already mentioned, which could obviously be of some benefit
in septic tanks and the like.
However, I did find a reference to a 1998 study into the "Efficacy of
saponin concentrate in grower and finisher diets for reduction of
odour in swine manure" !!:
and a similar use in poultry:
"There are several methods that have been used in the commercial
poultry industry to reduce aerial ammonia release from poultry manure.
.... Micro-Aid is a concentrated process extract from the Yucca
schidigera plant, formulated with other ingredients. This product
contains a combination of saponin surfactants plus a urease inhibitor.
It is designed to control the conversion of urea to ammonia and reduce
microbial proteolytic activity in the manure. ...As a result of these
reactions, the release of ammonia from the manure is supposedly
reduced. ...these reactions produce an increase in the nitrogen
content of the manure and also results in the precipitation of soluble
phosphorus of the manure which potentially reduces phosphorus runoff
So here is a roundabout way saponins potentially benefit water
A comparison study of Micro-Aid and other treatments follows with the
conclusion in part that:
"...manure application of an ammonia-reducing compound maybe effective
in reducing the mass generation rate of ammonia from laying hen
manure....the results reported on permeability of soils and leaching
of possible harmful nutrients in soils within turkey barns indicates
that contamination of ground water would not likely occur in the area
of the state where the study was conducted."
Clearly there is a lot of work being carried out into various aspects
of saponins, and there are lots of positive ways to present the
product without over-emphasising possible direct benefits in water