It received its name from the Latin, sapo, meaning soap. These saponins are the plant’s “immune system”. Saponins are widely distributed in the plant kingdom and many of these saponin-producing plants have soap as a part of their name:
• Soapwort – Saponaria officinalis
• Soaproot – Chloragalum pomeridianum
• Soapbark – Saponaria officinalis
• Soapnut – Sapindus mukorossi
The presence of the Latin name, saponaria, might also be a clue to the saponin content of the plant.
• Jaboncillo – Sapindus saponaria
• Soapwort – Saponaria officinalis
• Soapbark – Saponaria officinalis
Commercial saponin has been obtained from quillaja bark or from soaproot by extraction with water and subsequently with alcohol. The resultant saponin powder is not a pure chemical compound, but a mixture. It is powerfully sternutatory (causes sneezing). Saponin has been employed in foam baths and in hair shampoo. It may also be used as an emulsifier.1 They form oil-in-water emulsions and act as protective colloids.2
Safety and efficacy
Saponins cause haemolysis of blood, and if added to defibrinated blood may cause destruction of the red blood corpuscles. Dermatologically, when applied to normal healthy unbroken skin, saponin is not a primary irritant under the normal conditions of use and there is no evidence that it possesses sensitising properties. When taken by mouth, saponins are comparatively harmless. Sarsaparilla, for example, is rich in saponins but is widely used in the preparation of non-alcoholic beverages.3 Several in vivo tests show an antiinflammatory activity of crude saponin and hederagenin isolated from Sapindus mukorossi. Crude saponin and hederagenin inhibited the development of carrageenininduced edema in the rat hind paw as well as on granuloma and exudate formations induced by croton oil in rats. Additional crude saponin caused a significant inhibition of the development of hind paw edema associated with adjuvant arthritis in rats and inhibited the increase in vascular permeability and the number of writhings induced by acetic acid in mice.4
Chemistry
Saponins are glycoside compounds that are often referred to as natural detergents because of their ability to form foaming solutions in water. The majority of naturally occurring saponins are of the triterpenoidal type, with the steroidal based saponins forming a much smaller class. The steroidal saponins are based on a backbone of a (C30) triterpenoid saponin nucleus attached via C3 and an ether bond to a sugar side chain, whereas the steroidal are based on a choline (C27) steroid backbone. The aglycone of the triterpenoidal derivative is known as a sapogenin, whereas the steroidal aglycone derivatives are known as saraponins. The nonsaccharide portion (aglycone) of the saponin molecule is called the “genin” or “sapogenin”. Saponins are divided into three main classes depending on the type of sapogenin present:
w Triterpene glycosides – there are over 350 sapogenins and more than 750 triterpene glycosides in the triterpene glycoside class.
w Steroid glycosides.
w Steroid alkaloid glycosides.
The ability of a saponin to foam is caused by the combination of the non-polar sapogenin and the water soluble side chain present on the molecule. The foams tend to be stable and have been used in fire extinguishers as the foaming agent. They are also used to produce foam in beer and are responsible for the natural foam in root beer. They have been used as the foaming agent in toothpaste and are employed by local people where the plants occur as a shampoo and laundry detergent. Typical soap plants include yucca (Yucca schidigera), soapwort (Saponaria officinalis), soapbark (Quillaia saponaria), soaproot (Chlorogalum pomeridianum) and soapnut (Sapindus spp).
Triterpenoidal saponins
These are represented by lupeol, ?-amyrin and ?-amyrin.5 These saponins are found in a whole variety of foodstuffs, e.g. beans, lentils, soya beans, spinach and oats contain significant amounts.
Sapindus mukurossi – Indian soap nut
The soapnut tree (Sapindus species, Family: Sapindaceae) is known as arishta, aristaka or phenila in Sanskrit and ritha or reetha in Hindi. The Sapinaceae family are a family of about 150 genera and 2,000 species. The genera include Paullinia (180 spp), Sapindus (13 spp), Cardiospermum, Eriocoelum, Blighia and Radlkofera.3 The soapberry family comprises nearly 2,000 species, which are primarily tropical. The soapnut tree, also known as soapberry is known by the Indian names ritha, doadni, doda or dodan. In China and Japan it has been used as a remedy for centuries. In Japan the pericap is called “enmei-hi”, which means “life prolonging pericarp”, and in China “wu-huan-zi”, the “non-illness fruit”.6 It is found over most of the hilly regions of India. There are two major species, with the northern example being Sapindus mukurossi, and in the south, Sapindus emarginatus or Sapindus trifoliatus. The common name for these species is Indian filbert or soapnut. Sapindus mukorossi is one of the most important sources for saponins. The pericarp contains 10%-11.5% saponins, and is used locally for protection against pests and microorganisms. The powdered fruits (nuts) of these deciduous trees are traditionally used as a mild detergent for washing hair, as a hair tonic and for the management of dental caries. The leaves are used in a bath to relieve joint pain and the roots are used in the management of gout and rheumatism. The pericarp (shell) is a rich source of saponins that function as a mild detergent, cleanser, surfactant, antimicrobial and anti-inflammatory agent. Since ancient times, S. mukurossi has been used in East Asia and the Himalayan regions as a detergent for shawls and silks. The two triterpenoidal saponins containing hederagenin aglycone moiety have been isolated from the butanol soluble fraction of the fruits (without shells) of Sapindus mukorossi Gaertn.7
Sapindus spp – soapnuts: a review of the species
• Sapindus delavayi (Chinese name: Pyishiau- tzu, Japanese name: Hishoushi).
• Sapindus detergens is the Chinese soapberry.
• Sapindus drummondii. There is also western soapberry (Sapindus drummondii) found in Texas. The common name is derived from the fact that the fruits, when crushed in water, create great quantities of suds and were used by West Indian/Mexican natives as a laundry soap, floor wax and varnish.
• Sapindus indica is another soapberry.8
• Sapindus laurifolia Vahl. [Sapindus trifoliatus Linn, Sapindus marginatus Willd.] has the Kannada name, Antawalamara. It is said that the fruits are crushed and used as a soap.9
• Sapindus marginatus or soapberry is also found in the southern United States and Mexico and is also used as a substitute for soap.10
• Sapindus oahuensis Hillebr is lonomea or Çulu and is a species of flowering tree in the soapberry family, Sapindaceae, that is endemic to the islands of Kauaãi and Oãahu in Hawaiãi. Sadly this species is threatened by habitat loss.
• Sapindus saponaria var. drummondii (Hook. & Arn.) L. Benson or western soapberry. This was previously classified as Sapindus drumondii (Hook. & Arn.) (see above). The other common names include wild China tree, soapberry, Indian soap plant, cherrioni, jaboncillo. It is similar to the wingleafed soapberry.
• Sapindus saponaria L. var. saponaria or wingleafed soapberry is found from Arizona to Florida.
• Sapindus saponaria L. (Sapindaceae), popularly known as “sabão-de-soldado” and “saboeiro”, is a medium-sized deciduous tree occurring in the tropics, e.g. America and India, where the fruit is used as a soap and as a remedy against ulcers, scabies, joint pain, inflammations and skin lesions caused by fungi.11 Extracts from the dried pericarp of Sapindus saponaria L. (Sapindaceae) fruits were investigated for their antifungal activity against clinical isolates of yeasts Candida albicans and C. non-albicans from vaginal secretions of women with vulvovaginal candidiasis. Four clinical isolates of C. albicans, a single clinical isolated of each of the species C. parapsilosis, C. glabrata, C. tropicalis, and the strain of C. albicans were used. The hydroalcoholic extract was bioactivity-directed against a clinical isolate of C. parapsilosis, and showed strong activity. The n-BuOH extract and one fraction showed strong activity against all isolates tested. The saponins isolated showed strong activity against C. parapsilosis.
• Sapindus trifolatus also contains saponins but has smaller fruits that contain less saponin.12 The complete nut weighs around 4 g (the inner kernel around 1.7 g and the outer shell or pericarp 2.3 g). The inner kernel has a tough black outer skin that houses a woody pulp, which has little or no surfactant qualities. The pericarp, on the other hand, produces a tight creamy foam that has outstanding stability even after 24 hours.
Commercial suppliers
There are a number of good sources for this material with high activity.
Bio-Botanica Inc Bio-Saponins INCI name: Saponins and is composed of Smilax Aristolochiaefolia (Sarsparilla) Root Extract, Dioscorea Villosa (Wild Yam) Root Extract, Quillaja Saponaria (Quillaja) Bark Extract, Yucca Schidigera (Yucca) Extract and Glycerin. CAS No: 11006-75-0, 8047-15-2 EINECS No: 232-462-6
Het-Cam evaluation
The blend was evaluated for ocular irritancy potential with the Hen’s Egg Test, utilising the ChorioAllantoic Membrane (HET-CAM). Under the conditions of the test, the results indicated that the product at 10% showed practically no ocular irritation potential.
Surface tension
It was also compared to Tween 80 and sodium lauryl sulfate (SLS) on an equivalent dry weight basis. The surface tension was measured using a laboratory surface tensiometer. The surface tension reduction capability of the blend was similar to Tween 80 and only slightly less than SLS.
Foaming index
The foaming index is the highest degree of dilution of an aqueous decoction of a material, which produces persistent foam under the conditions specified. The foaming index was determined from an aqueous solution of the blend, Tween 80 and SLS. The solutions were prepared on an equivalent solids basis. Results showed that the blend was better than the other two at low concentrations (0.1%).
Foam stability
Foam stability was determined on 1% solutions of the three test materials. The solutions were vigorously shaken to establish “good foam”; then the foam height was determined as a function of time. The new blend had better foam stability than Tween-80 or SLS.
Kaden Biochemicals through Symrise Neo Actipone Soap Nutshell INCI name: Sapindus Mukurossi Peel Extract. It is approved by ECOCERT SAS F 32600 according to the ECOCERT standards for natural and organic cosmetics. The extract is readily biodegradable (OECD 301B). Neo Actipone Soap Nutshell is obtained from the soapnut tree (Sapindus mukorossi), which grows in warm temperate to tropical regions. The wild harvested fruits are small orange coloured drupes with 1-2 cm diameter, known as soap nuts. In India, the soap nuts are commonly used for washing hair, clothes and for polishing jewellery. Exhibiting an excellent cleaning performance Neo Actipone Soap Nutshell is a natural and mild alternative to synthetic surfactants.
Desert King International Andean QD Ultra Andean QD Ultra is a spray-dried purified (available as powdered and aqueous solution) Chilean soap bark tree (Quillaja Saponaria Molina), with an average composition as follows: Moisture content 2.00 – 7.00% Fibre 0.01 – 0.50% Proteins 3.50 – 7.00% Ash 6.50 – 12.00% Fats 0.01 – 0.50% Carbohydrates 73.00 – 87.94% Triterpenic saponins solutions are acidic, but neutralisation with alkali (e.g. triethanolamine, sodium hydroxide, arginine etc.) does not modify their stability, although a slight browning of the colour is observed that can easily be returned by restoring the pH with lactic acid.13 A 10% saponins solution will maintain transparency by successive ethanol addition up to a maximum of 20%, but the opacity increases at higher levels.13 Purified quillaja triterpenic saponins, when used alone, have an average foaming power which is about 40% lower than for most high-foaming surfactants. It was noted that a blend prepared with coco-glucoside, in the ratio 80:20, has foaming power better than when it was prepared with SLES. Foam quality remains in all cases, optimal, i.e. small, homogeneous bubbles. There is positive synergic interaction between natural polymers and quillaja triterpenic saponins in aqueous solution. Saponins dramatically increased the thickening power of carrageenan-type and xanthan gum polymers. The presence of polymer also increased the foaming power of the saponins solution. The addition of both polymers noticeably increased the foam stability, without decreasing its height and quality.12
Dr H. Schmittmann Saponin 374 This is sold as a powder but we are unable to ascertain the source or activity at the time of writing.
Sabinsa Corporation (through Unifect in UK) Sapindin INCI name: Sapindus Trifoliatus Fruit Extract CAS No: 223748-41-2 Chemistry: Saponins - minimum 60% saponins Cosmeceutical applications: Natural surfactant (haircare), antimicrobial.14 A standardised, powdered extract prepared from the fruit (nuts) of Sapindus trifoliatus. Sapindus extract has been used as a detergent for centuries and is listed in the Japanese Cosmetic Ingredient Codex (JCIC) as an ingredient authorised for use in cosmetics by the Ministry of Health and Welfare in Japan. Dermal toxicity studies on the saponin fraction indicated that the material did not show any dermal irritation, sensitisation, phototoxicity or photosensitisation effects.6
Conclusions
The use of saponins as detergents and emulsifiers has been on the wish list for nearly twenty years and it is only recently that the commercial availability and quality of the material has been developed. It is believed that the potential benefits would justify further investigation in a wide range of personal care products. PPCC
Acknowledgement
The author would like to thank Mr. Paul Rogers (LF Beauty) for his help in assembling additional data for the suppliers of saponins and for his valuable contribution.
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