an overview of alkyl polyglucosides pertaining to personal care products
Today, many surfactants are made from oleochemicals (vegetable origin) as opposed to petrochemicals (petroleum origin) and are also biodegradable. Oleochemicals, as oils and fats are employed to synthesize these surfactants and include palm and coconut oils. These surfactants include the nonionic alkyl polyglucosides (being the largest group of sugar-based surfactants manufactured worldwide), and are produced from fatty alcohols derived from coconut or palm and glucose from corn starch or other sources of renewable carbohydrates employing green chemistry (1).
[NB. There are other sugar-based surfactants, the most important being (a) sorbitan esters which are nonionic surface active agents; being partial esters of the common fatty acids (lauric, palmitic, stearic and oleic) and sorbitol, a sugar alcohol made from corn syrup, used as emulsifying agents. And (b) sucrose esters which are nonionic surface active agents obtained by esterifying sucrose with edible fatty acids from palm oil, used as emulsifiers with a pronounced skin feel. Other sugar-based surfactants mentioned in the literature are Methylglucoside esters and Anionic alkyl polyglucoside derivatives, both of which have limited production. All four of these surfactants are not subject to a detailed presentation within this article as they are considered, at this stage, to be less impressive property-wise than the nonionic alkyl polyglucosides].
Alkyl polyglycosides, are typically complex mixtures of compounds with different sugars comprising the hydrophilic (water loving) end and alkyl groups of variable carbon length comprising the hydrophobic (water repelling) end. This characteristic with both water soluble and oil soluble ends is referred to as amphiphilic. Each particular end of the molecule combines with a different environment and joins them together thereby solubilizing one into the other thus producing molecules of dirt and oil which loosen and dissolve in the water. When derived from glucose, they are known as alkyl polyglucosides (APG's) with decyl, lauryl, and coco to name but a few, their names change due to the variance in the length of the carbon chain. (Which is explained later). Hence, glucose being a sugar and a critical component of these compounds they are often referred to as "sugar surfactants".
Raw materials for the manufacture of APG's Fatty alcohols.
Fatty alcohols can be obtained either from petrochemical sources (synthetic fatty alcohols) or from natural, renewable resources, such as fats and oils (natural fatty alcohols). Fatty alcohol blends are used in the APG synthesis to build up the hydrophobic part of the molecule. The natural fatty alcohols are obtained by chemical process of the fats and oils (triglycerides),. As an example, the desired alkyl chain lengths of the fatty alcohol, are obtained from the main feedstocks of oils and fats composed from coconut or palm kernel oil (C12/14 range) and tallow, palm rapeseed oil (for the C16/18 range).
The hydrophilic part of the alkyl polyglucoside molecule is obtained from carbohydrate. Carbohydrates such as starch from corn, wheat or potatoes, are suitable as base raw materials for the production of alkyl polyglucosides. Certain types of carbohydrates (consisting of many repeating structural units) include starch [both constituents of Starch (Amylose and Amylopectin) are, in turn, composed of linked chains of Glucose] or glucose syrups. But other types of carbohydrates (consisting of a single component) can be obtained from different forms with glucose as the main component, these include anhydrous glucose, glucose monohydrate (dextrose) or highly degraded glucose syrup. But financial restraints play an important factor as the use of processed glucose and dextrose are substantially more costly.
Examples of the more commonly used APG's and their base materials are presented herewith. Decyl glucoside is produced by the reaction of glucose from corn starch with decyl alcohol which is derived from coconut.
Lauryl glucoside is produced from glucose and lauryl alcohol which is derived from coconut.
Coco-Glucoside is the product obtained by the condensation of coconut alcohol with glucose.
Caprylyl/Capryl Glucoside is the product obtained by the condensation of a mixture of caprylic and decyl alcohols with glucose. The fatty alcohols (Coconut and Palm Oil) and glucose are from vegetable origin.
APG's. However, originate back to the 19th century: In 1893, the German chemist Emil Fischer combined fatty alcohols and glucose obtained from coconut or palm kernel oil and starch for the first time, creating a new category of substances called alkyl polyglucosides. ( Fischer E. Uber die Glucoside der Alkohole. Berichte. 1893;26:2400-2412.) Interestingly, a patent (Process for the production of glucosides of higher aliphatic alcohols US 2049758 A) was granted to H. Th. Bohme AG of Chemnitz in 1934 (due to the potential interest of glucosides as surface active agents) but interest waned into insignificance for a long time primarily because they were difficult to make and there were many other surfactants being produced.
It was to take almost one hundred years, however, to progress from simple laboratory experiments and one patent of limited technology of the day to the industrial production of APG surfactants and their use in formulations. In 1989, a German company succeeded in designing an industrial production process for APG surfactants, following a costly and complex research and development effort.(2) It was not until the mid 1990"s that full production took place. APG surfactants were originally developed for home care and body wash applications. Nowadays the applications for APG surfactants are present in a diverse range of products including baby foam bath products to facial cleansing lotions, shampoos, and oral care products, from wipes to laundry detergents, hard surface cleaners, and industrial cleaning applications.(3)
As stated above Alkyl polyglucoside surfactants are obtained from renewable, plant derived raw materials and therefore are suitable for products where mildness to human skin, environmental compatibility and high performance are paramount. Alkyl polyglucosides have been extensively tested in various eco-toxicological studies.(4) No environmentally harmful intermediates are formed even during the biodegradation end process of mineralization to carbon dioxide and water.(5) Nor do the surfactants release any undesirable by-products such as nitrogen, ethylene oxide, or preservatives. As they do not contain nitrogen they therefore cannot contribute to nitrosamine formation. For all these reasons, many formulators view alkyl polyglucosides as ideal “green” surfactants which add significance to their products and help them to differentiate these products from traditional ones.
In fact, within the structure of international regulations governing eco-friendly products, alkyl polyglucosides meet the requirements for highly accepted green labels. They can be recommended for natural cosmetics concepts such as NATRUE, ECOCERT*, BDIH, COSMOS, NPA, NSF_QAI and FDA GRAS (filed on December 19, 2007, and designated it as GRAS Notice No. GRN 000237) and can also be considered for use in products formulated according to EU Ecolabel, Nordic Swan and BraMiljöval standards. (6)
In addition to their ecological footprint, alkyl polyglucosides are not toxic or harmful to human health and show a lower skin irritation than other surfactants. It is essential that the surfactants used in personal care products have a minimal irritation potential because it is inevitable that these products come within intimate contact with the skin. A comparative study (7) of various surfactants showed that alkyl polyglucosides possess superior mildness compared to other surfactants encountered in the marketplace, confirming the well-known association of “greenness” with mildness.
Alkyl polyglucosides can satisfy these requirements based on their exceptional skin compatibility and deep pore cleansing properties for personal care products. One property that complements the cleansing process is the formation of foam. Consumers perceive the formation of foam as an inherent part of the cleaning phase in personal care products such as shampoos and shower gels. Alkyl polyglucosides, alone or in combination with other surfactants, produce foam which is voluminous and of desirable cell structure with excellent stability in all the above-mentioned applications.
APG's exhibit a superior conditioning effect on hair with regards to wet/dry compatibility than betaine, which is the preferred co-surfactant in shampoo formulations worldwide. This would be of great assistance in developing alternatives to silicone within a system utilizing vegetable oil based emollients, waxes, and polymers.(8)
Additional benefits that formulators regard as positive in alkyl polyglucosides include the absence of ethoxylates or sulfates in their composition and their stability over a wide pH range.
The carbon chains of the more common or frequently used APG's are listed below-
Caprylyl/Capryl Glucoside C8-10 Lauryl Glucoside C12-14 Decyl Glucoside C8-16 Coco Glucoside C8-16
Final Safety Assessment
Decyl Glucoside and Other Alkyl Glucosides as Used in Cosmetics, December 19, 2011 (9) Cosmetic Ingredient Review (CIR) Other alkyl polyglucoside ingredients that may be used in cosmetics include Arachidyl Glucoside, C12-20 Alkyl Glucoside, Cetearyl Glucoside, Ethyl Glucoside. Decyl Glucoside and the other alkyl glucoside ingredients may be utilized in baby products, bath products, cleansing products, skin care products, eye makeup and hair care products. In cosmetics and personal care products, Decyl Glucoside, Lauryl Glucoside, Arachidyl Glucoside, Caprylyl/Capryl Glucoside and Coco-Glucoside are indicated as surfactants/cleansing agents. C12-20 Alkyl Glucoside and Cetearyl Glucoside are indicated as surfactants/emulsifying agents, while Ethyl Glucoside is indicated as a skin conditioning agent/humectant.
Safety Information: The safety of Decyl Glucoside, Arachidyl Glucoside, C12-20 Alkyl Glucoside, Caprylyl/Capryl Glucoside, Cetearyl Glucoside, Coco-Glucoside, Ethyl Glucoside and Lauryl Glucoside has been assessed by the Cosmetic Ingredient Review (CIR) Expert Panel.
The CIR Expert Panel evaluated the scientific data and concluded that these ingredients were safe for use in cosmetics when formulated to be non-irritating. More safety Information: CIR Safety Review: The CIR Expert Panel reviewed a study that indicated that Caprylyl/Capryl Glucoside was not readily absorbed through the skin. At high concentrations Caprylyl/Capryl Glucoside was irritating and long-term skin irritation resulted in other adverse effects. (It must be noted that these observations were obtained on trials with rabbits "The researchers stated that irritation, inflammation, and stress in these animals were major contributing factors to many, if not all, of the toxicologic effects; however, the researchers also stated that it is possible that caprylyl/capryl glucoside produced some of the effects"). [However, the writer notes that rinse-off formulations with Caprylyl/Capryl Glucoside at levels of over 20% are presented in commercial literature and purporting to comply with BDIH guidelines]. No other adverse effects were observed at concentrations that did not cause skin irritation. With APGs of varying chain length (C8/10 to C12/16; 15-70% active ingredient), there was a structure-response relationship with irritation potential decreasing with increasing chain length. Lauryl Glucoside was not a reproductive or developmental toxicant. Alkyl glucoside ingredients have not been found to be genotoxic. Clinical tests of products containing alkyl glucoside ingredients have found that the products were not dermal irritants or sensitizers.
Based on the data reviewed, the CIR Expert Panel concluded that the alkyl glucoside ingredients, including Decyl Glucoside, Lauryl Glucoside, Arachidyl Glucoside, Caprylyl/Capryl Glucoside and Coco-Glucoside were safe for use in cosmetics when formulated to be non-irritating. Decyl Glucoside, Arachidyl Glucoside, C12-20 Alkyl Glucoside, Caprylyl/Capryl Glucoside, Cetearyl Glucoside, Coco-Glucoside, Ethyl Glucoside and Lauryl Glucoside may be used in cosmetics and personal care products marketed in Europe according to the general provisions of the Cosmetic Regulations of the European Union. Final Safety Assessment Decyl Glucoside and Other Alkyl Glucosides as Used in Cosmetics December 19, 2011 Cosmetic Ingredient Review (CIR) (9)
However, further to the above Review, the Panel have now (2013) noted that - Most of these ingredients function as surfactants in cosmetics, but some have additional functions as skin-conditioning agents, hair-conditioning agents, or emulsion stabilizers. The Panel reviewed the available animal and clinical data on these ingredients. Since glucoside hydrolases in human skin are likely to break down these ingredients to release their respective fatty acids and glucose, the Panel also reviewed CIR reports on the safety of fatty alcohols and were able to extrapolate data from those previous reports to support safety. (10)
APG's are considered to be one of the "New generation of surfactants". In the European Community, where the restrictions in place regarding cleansers, cosmetics, are the world's strictest, (under the EU Cosmetics Directive). Example Performance Properties of Certain Individual APG's Decyl Glucoside generates an exceptional foam for a nonionic surfactant, whatever the conditions. It produces a very satisfactory level of foam, comparable with that obtained using conventional anionic surfactants. Moreover, the foam obtained is particularly stable, which is an advantage for the formulation of bubble baths and shower gels. The foam generated is fine and stable.
Furthermore, because of its wide range of compatibility, Decyl Glucoside can be combined with all types of surfactants without reducing foam volume or stability. Decyl Glucoside, used as co-surfactant, can reduce the total active ingredients content of foaming formulas without altering their performance as cleansing effectiveness, foam volume, and ease of thickening, are maintained. Lauryl glucoside can be used alongside other glucosides to enhance the foam and skin conditioning properties. It can also be used in ionic formulations to add foam depth and emulsifying properties. Lauryl Glucoside possesses thickening properties when combined with both nonionic and anionic sufactants. Coco Glucoside works as a surfactant, foaming agent, conditioner and emulsifier. It helps increase the foaming capacity of a solution, and is particularly useful in hair care products, in which it has the ability to smooth out the hair structure and increase manageability This ingredient is compatible with all skin types and gentle enough to be used in baby products. The Duhring Chamber Test lists it as having the lowest irritation score of all common surfactants. Caprylyl / Capryl Glucoside is an ideal solubilizing agent for foaming products because it solubilizes essential oils, fragrances and preservatives but also boosts foam volume. Its mild cleansing effect is interesting for the formulation of make up removers, especially lotions.
Summation of Properties of APG's as utilized in Personal Care products- (Personal Care Products are manufactured consumer products used in personal hygiene and for beautification whereas cosmetics are solely for beautification and can be classed as luxury items).
Produced from natural, renewable resources.
Compatible with all other surfactant classes
Reduces irritation potential of irritant surfactants.
Selective ones are excellent solubilizers replacing standard EO compounds (polysorbatesetc).
Outstanding foam behavior
Replacement foam boosters for standard DEA compounds(eg coconut diethanolamide).
Excellent eco-toxicological profile
Ethylene oxide free
Improves tensile strength of hair
Modifies interaction of dry hair (5)
Extremely mild surfactant/emulsifier
Function in hard water
Stable over desired pH range
Excellent skin compatibility
Intensive and gentle cleansing
By way of an example, the following demonstrates the potential of APG's in such products that are non-topical and posses therapeutic qualities. APG's of C12-14 have been used in toothpastes and various oral hygiene formulations. Also, APG/fatty alcohol sulphate mixtures demonstrated increased mildness with regards oral mucous membranes simultaneously producing a copious foam. C12-14 APG's have proven to be a capable promoter for certain antibacterial compounds, such as chlorhexidine. Combined with an APG the amount of the antibacterial compound can be reduced by 75% without any depletion of activity. This leads to the availability of high-active mouth rinses with an acceptable taste and the non discolouration of teeth which if the APG were absent would produce a product of undesirable quality (11).
Cosmeceutical and Pharmaceutical Applications:
There are no doubt further applications for APG's will be pursued within the personal care industry and this has now extended to cosmeceuticals (12) as one example, and onto pharmaceuticals as further properties will be examined and utilized. (It is not the intention of the writer or within the scope of this overview to present the numerous and highly technical and detailed relevant drug-based studies that are available). However, in order to illustrate, the following is but a small sample of studies carried out regarding APG's and their dermal delivery with reference to pharmaceuticals. Examples of pharmaceutical utilization of APG bases could be considered as preferential option in drug compounding related to the conventional ones re Jaksic et al.2012 (13). Also, results indicated a good safety profile of alkylpolyglucoside surfactant re Savić et al. 2007 (14).
APG's were also used in the design of microemulsion systems loaded with ascorbic acid (15) and insulin (16). As suggested by Rybinski et al. (17) alkyl polyglycoside-based microemulsions are potential systems that have very low interfacial tensions and are very largely electrolyte and temperature independent and are therefore highly suited to various pharmaceutical dosage forms.
Water in oil emulsions based on lecithin and Coco glucosides or decyl glucosides were developed in order that they could be safely used to promote transdermal delivery of 5 fluorouracil (an anti-cancer drug). Decyl glucoside-based systems were more promising and showed greater permeation than coco glucoside-based systems. It was noted that further studies need to be carried out, where this promising emulsion (in a suitable lipogel base) can be evaluated for its potential as a patient-friendly dosage form in promoting the transdermal delivery of this active through human skin (18).
The FDA certification of an alkyl polyglucoside surfactant for topical formulation presents a significant step in the process of recognition. This could lead onto further research into the potential benefits of naturally derived materials in both conventional and new drug delivery systems (19). From the foregoing it would appear that APG's have gained general acceptance as surfactants for 'actives' within dermal delivery systems. Previously it has been extremely difficult to achieve topical bioavailability of hydrophilic active compounds as it must be remembered that in order for actives to effect desirable concentrations the stratum corneum has to be penetrated. But as the stratum corneum has lipophilic (oil loving) properties, hydrophilic compounds exhibited poor penetration. However, it has now been demonstrated that APG's have shown to assist in this area of dermal delivery by way of topical application. This therefore can be extended to personal care products with the potential for products to possess greater 'activity' than previously formulated.
Obviously APG's produced with "green chemistry" will hold a prominent and important position within the personal care industry even though it took over 100 years for them to come to the fore! There is a possibility that they could replace traditional petroleum and maybe other natural oils-based surfactants. As an indication their estimated Production Capacity, Worldwide is 85,000 tonnes per annum across areas of application.(20) and there appears to be continued growth within the future. There is no doubt that APG's will dominate the 'surface active agent' personal care market as, at this moment of time, there appears to be a nonexistence of surfactants that can match their impressive credentials with regards to origin, biodegradability, chemical properties and dermatological acceptability when topically applied to the human skin.
1. 12 Principles of Green Chemistry* 1. Prevention of waste 2. Atom Economy 3. Less Hazardous Chemical Synthesis 4. Designing Safer Chemicals
5. Safer solvents and auxiliaries 6. Energy efficient 7. Renewable feedstocks 8. Reduce derivatives
9. Catalysis 10. Design for degradation 11. Real time analysis for pollution prevention 12. Safety * Anastas, P.T., Warner, J. C., Green Chemistry: Theory and Practice, Oxford University Press, New York (1998).
2. Hill, K., von Rybinski W., Stoll G. (1997) Alkyl polyglycosides: Technology, properties and application. Ed. VCH, Germany. pp 1-7;71-130.
3. APG Factsheet-Eng-Final-Neu.pdf
4. Willing A., Messinger H., Aulmann W. (2004) “Ecology and Toxicology of Alkyl polyglucosides”. In: Handbook of Detergents. Ed. U.Zoller, Marcel Dekker, New York, pp. 487-521.
5. www.skin-care-forum.basf.com/docs/...1-20/scf12_gb_may1995.pdf?... 6.http://www.cossma.com/fileadmin/all/cossma/Archiv/SciencArtic/COS1308_20_B ASFFormular.pdf
7. Mehling A., Kleber M., Hensen H. (2007) Comparative studies on the ocular and dermal irritation potential of surfactants. Food Chem. Toxicol. 45, 747-58
8. Tae Seong Kim, Yun Jun Huh, Juntao Xia, Vicky Zhang
The use of alkyl polyglucosides as alternatives to silicones in shampoos. December 2012
Including references- Hill, K., Alkyl polyglycosides - Where "green" meets performance, SOFW-Journal, 135, 6 (2009).
10. Fiume MM, Heldreth B, Bergfeld WF, Belsito DV, Hill RA, Klaassen CD, L iebler D, Marks JG Jr, Shank RC, Slaga TJ, Snyder PW, Andersen FA. Safety assessment of decyl glucoside and other alkyl glucosides as used in cosmetics.Int J Toxicl 2013 Sep;32(5 Suppl):22S-48S. doi: 10.1177/1091581813497764
11. EP 0 304 627 A2, Henkel KGaA, 21. 07. 1988.
12. Tasic-Kostov M, Pavlovic D, Lukic M, Jaksic I, Arsic I, Savic S Lactobionic acid as antioxidant and moisturizing active in alkyl polyglucoside-based topical emulsions: the colloidal structure, stability and efficacy evaluation Int J Cosmet Sci. 2012 Oct;34(5):424-34. doi: 10.1111/j.1468-2494.2012.00732.x. Epub 2012 Jul 12.
13. Jaksic, I., Lukic, M., Malenovic, A., Reichl, S., Hoffmann, C., Müller-Goymann, C., Daniels, R. and Savic, S. (2012). Compounding of a topical drug with prospective natural surfactant-stabilized pharmaceutical bases: physicochemical and in vitro/in vivo characterization--a ketoprofen case study. Eur J Pharm Biopharm, 80(1):164 175.
14.., Savić M., Tamburić, S., Vuleta, G., Vesić S. and Müller-Goymann, C.C.(2007). An alkylpolyglucoside surfactant as a prospective pharmaceutical excipient for topical formulations: The influence of oil polarity on the colloidal structure and hydrocortisone in vitro/in vivo permeation. Eur J Pharm Sci, 30(5):441-450.
15. Pakpayat N, Nielloud FR, Fortuné C, Peteilh T, Villarreal A, Grillo I, et al. Formulation of ascorbic acid microemulsions with alkyl polyglycosides. Eur J Pharm Biopharm. 2009;72:444–452. doi: 10.1016/j.ejpb.2009.01.005.
16. Graf A, Ablinger E, Peters S, Zimmer A, Hook S, Rades T. Microemulsions containing lecithin and sugar-based surfactants: Nanoparticle templates for delivery of proteins and peptides. Int J Pharm. 2008;350:351–360. doi: 10.1016/j.ijpharm.2007.08.053
17. Rybinski WV, Guchkenbiehl B, Tesmann H. Influence of co-surfactants on microemulsions with alkyl polyglycosides. Colloids Surf A. 1998;142:333–342. doi: 10.1016/S0927-7757(98)00527-5.
18. Aliaa Nabil ElMeshad and Mina Ibrahim Tadros Transdermal Delivery of an Anti-Cancer Drug via W/O Emulsions Based on Alkyl Polyglycosides and Lecithin: Design, Characterization, and IN VIVO Evaluation of the Possible Irritation Potential in Rats. AAPS PharmSciTech. 2011 March; 12(1): 1–9. Published online 2010 December 9. doi: 10.1208/s12249-010-9557-y
19.. Savić S., Tamburić, S., Savić MM From conventional towards new - natural surfactants in drug delivery systems design: current status and perspectives Expert Opin Drug Deliv.2010 Mar;7(3):353-69. doi: 10.1517/17425240903535833.
20. Sugar-Based Surfactants: Fundamentals and Applications Cristóbal Carnero Ruiz CRC Press, 12/12/2010 - Science- 664 pages
Other information extracted from- >Hill, K., von Rybinski W., Stoll G. (1997) Alkyl polyglycosides: Technology, properties and application. Ed. VCH, Germany.
Nonionic Surfactants: Alkyl Polyglucosides Dieter Balzer (Editor), Harald Luders (Editor) Publisher: CRC Press; 1 edition (July 12, 2000)
Sugar-Based Surfactants: Fundamentals and Applications Cristóbal Carnero Ruiz CRC Press, 12/12/2010 - Science- 664 pages
Novel Surfactants: Preparation Applications And Biodegradability, Second Edition, Revised And Expanded Editor(s): Krister Holmberg Published: July 3, 2003 by CRC Press
Numerous sources of information from non-commercial web sites, patents and subscription newsletters.
'Nutracos' Dec 28th 2013 (Mod: Oct19/14)