Formulating Hair Conditioners With Naturals

What does it mean to condition hair naturally, if not simply to deliver conventional conditioning benefits with materials that fit some scheme of acceptable natural ingredients? To summarize the performance expected from hair conditioners as outlined in an earlier “Formulating With Naturals” column on natural hair care,¹ an adequate product would reduce the force of both wet and dry combing, prevent snags, reduce the final surface charge to reduce fly-away with an antistatic effect, make hair mass more manageable and allow the consumer to style hair with ease. Other parameters cited could include wet and dry feel, gloss or shine, strengthening, and even color and UV radiation protection.²

This column proposes that the current natural and organic hair conditioner market can de divided into two types—those that are effective but use technology considered suspect under most natural certifications, i.e., “greenwashed,” and those that are more compliant with natural and organic certification but are found by consumers to have performance gaps. Both the development of new ingredients, mostly those naturally derived based on acceptable chemistries, and formulation techniques can potentially move the cosmetic industry into better performing conditioners within generally accepted natural guidelines.

Natural Conditioning Basics

Every good chef must know the ingredients before experimenting beyond the confines of conventional cuisine, so this column will first look at the overall composition of rinse-off conditioners.

Whether directed towards the natural or conventional markets, basic hair conditioners contain from one to a number of cationic quaternary ammonium surfactants in lotions of varying thickness formed from a gel network of liquid crystalline co-emulsifiers, primarily cetyl and stearyl alcohols. In looking at natural conditioner labels, many promote a natural ingredient such as shea butter or argan oil being used in a less than natural formulation, such as a conventional quat formula. Many of these products, in fact, reflect “greenwashing,” especially since the standards for natural labeling remain variable and mostly self-administered. Some product labels claim more than 70% certified organic ingredients using organic certified aloe vera juice (gel) and various vegetable oils while depending on quaternary ammonium chloride quats for conditioning performance on the hair. They, too, occasionally include a form of silicones. A favorite among natural market conditioners is behentrimonium chloride or methosulfate, but stearalkonium and cetrimonium chloride are also widely used. In many cases, the ingredient labels are laden with botanicals and vegetable oils listed by their binomial Latin or Linnaean names to camouflage the basic functional ingredients.

The WEN product by Chaz Dean took a novel approach to natural hair conditioning with its Sweet Almond Mint Cleansing Conditioner, which uses behentrimonium methosulfate, stearamidopropyl dimethylamine and amodimethicone in a fatty alcohol base with polysorbate 60 and PEG-60 almond glycerides to assist emulsification. While the product claims to be “made with a perfect blend of herbs and natural ingredients,”³ the conditioning effect depends on the performance of a combination of a quat, a fatty amine and a silicone derivative much more than the added natural ingredients, although the sweet almond oil does contribute conditioning properties.

Natural Conditioning Dilemmas

The hair that needs the most conditioning usually is the hair that has been most damaged, especially by chemical treatments. Seeking natural conditioners while using redox reactive chemistries like oxidative styling, bleaching, and reductive and alkaline perm and relaxing may seem contradictory; however, the need is present and will be addressed. Abused hair needs a little tender loving repair after this self-inflicted damage, but delivering that care naturally and avoiding common conditioning agents such as fatty quaternary ammonium compounds and silicones can be challenging.

The lack of quats as acceptable materials in any of the common natural standards is a challenge to creating a natural certified conditioner formula. Most standards beyond the U.S. Department of Agriculture’s (USDA) National Organic Program (NOP) will allow fatty alcohols, since they are produced through hydrogenation of naturally occurring fats and oils. NSF International and the American National Standards Institute’s (NSF/ANSI) NSF/ANSI 305, the Standard for Personal Care Products Containing Organic Ingredients, is claimed to be the most appropriate standard to follow beyond the USDA Certified Organic by Quality Assurance International (QAI) professionals.⁴ USDA NOP standards have a short approved list of acceptable additional ingredients in certified organic products, even in the > 70% organic tier. In this case, the only acceptable preservative would be alcohol, and all the semi-synthetic additives essential for most cosmetics would not be available. The rationale then for following standards by these other organizations becomes apparent.

Building a Natural Conditioner

Using the current toolbox available for natural and organic personal care formulations, reasonably well-functioning rinse-off conditioners can be constructed by piecing together components based on their functionality in the product and on the hair.

Viscosity: Rinse-off products generally have a substantial viscosity in the bottle for easy application with no dripping, yet they are easy to spread and distribute through the hair regardless of length or curl. Conventional products currently employ thickening systems designed to yield shear thinning creams based on establishing liquid crystalline gel networks composed of hydrated amphiphiles or co-emulsifiers, coupled with adequate amounts of more hydrophilic surfactants acting as primary emulsifiers. While these systems do not necessarily contain oils, they do in many cases; note this same strategy is used when formulating skin creams and lotions.

Base ingredients: The primary base ingredients comprise a blend of fatty alcohols, often cetyl and stearyl, with more hydrophilic emulsifiers to structure the lyotropic mix in water. The fatty alcohols rate acceptable by most certification standards beyond USDA NOP because they derive from hydrogenation and or hydrogenolysis of natural oils and fats. The formulator must decide what surfactant to choose to create the gel network.

Surfactants: Although exceptions exist, cationic quaternary ammonium salt surfactants are unacceptable to most natural standards. However, there is widespread use of these surfactants in products claimed to be natural. One notable exception is behentrimonium chloride, which is accepted in conditioners for the Whole Foods body care target market.

Emulsifiers: Alternate hydrophilic emulsifiers chosen to complex with conditioner cream fatty alcohols can come from a range of acceptable (non-PEG) nonionic classes, primarily sugar esters such as alkylglycosides and polyglyceryl esters. Sucrose cocoate and sucrose stearates, with sucrose being a disaccharide with multiple hydroxyl groups, can function across the HLB range with mono and di-ester combinations of varying alkyl chain lengths. Alkyl glycosides, more widely employed in natural creams, primarily use glucose as the hydrophile, but an unusual range of alkylpolypentosides uses five carbon sugars from wheat straw as their base—and are capable of creating milky white emulsions. A wide range of creams and lotions can be made using the commercially available alkyl glucosides, since they all contain sufficient unreacted fatty alcohol to form the balanced lyotropic mesophases that help stabilize the disperse phase in low and high viscosity emulsions.

The range of polyglyceryl esters used as food emulsifiers, which are based on dehydrating polymerized glycerin, also yield a full complement of HLB emulsifiers, and are supplanting the more conventional ethoxylated nonionics in natural formulation.

Stabilizers: Stable systems in a wide range of viscosities can be formulated with added solid amphiphiles. Further investigations of other emulsion stabilizing technologies, such as cellulose fiber based products from microcrystalline cellulose to Citrus aurantium sinensis (Orange) fibera (purified citrus pulp), will work their way into conditioner technology in the near future.

Conditioning: As previously noted,¹ one unique choice for conditioner cream bases is brassicyl isoleucinate esylate, the use of which was recently patented by its supplier as a non-petrochemically derived cationic surfactant that increases substantivity of compositions on skin and hair.⁵ The various commercial versions of this rapeseed derived emulsifier retain a significant portion of unreacted brassicyl alcohol (C18–22) to yield a gel network that provides the cream structure while the “esylate” (ethane sulfonate) neutralized amino acid ester delivers conditioning. Suggested use involves adjusting the normally low pH with free base arginine—the unusual basic amino acid that finds a home as the starting material for other naturally derived surfactants.

Lauroylarginine was reported⁶ to show an affinity for hair binding ionically between pH 4–9, above which the hair negative charge attracts arginine’s positive charge well into the alkaline pH range. Pyrrolidone carboxylic acid ethyl cocoyl arginate is a cationic surfactant building on this same arginine ester technology and is useful for conditioning in rinse-out and leave-in conditioners that are capable of foaming in dilute water solution. Oshimura found the guanidinium group of arginine to have an acid dissociation constant of pH 9.04 with ionic attraction to hair below about pH 9.7 Surface charge: The isoelectric point of hair is estimated at pH 4.0; therefore, the surface charge is negative above pH 4 and positive below pH 4 based on the keratin protein. In other words, the surfactant or polymer will be ionically attracted to hair within the range of pH 4 and the isoelectric point pH of that material. Robbins differentiates between the isoelectric pH point, where a particle or protein will not move in an electrical field (electrophoresis) and the isoionic point, where there are equal amounts of positive and negative sites by titration.8 This isoionic point is between pH 5.6–6.2. Chemically treated hair presents a much more hydrophilic, negatively charged surface to the oxidized residues of cysteine–cysteic acid, which results in a sulfonic acid terminus. Therefore, conditioning treatments above cysteic acid’s pKa1 of 1.89 should, theoretically, “stick.”

Amphoteric surfactants can work here by presenting both positive and negative, i.e., zwitterionic, charges at their isoelectric points, with laurylbetaines having predominantly cationic character below pH 5.5.⁹ Other amphoterics reportedly have isoelectric points in the range of pH 3.5–6.5, below which they should have that sticky positive charge. Rosen claims that this adsorbtion does not result in formation of a hydrophobic film.¹⁰ He reports the isoelectric point for beta-N-alkylaminopropionates as ~pH 4, and notes that they function well to emulsify fatty alcohols. A trial and error series of experiments would be warranted to determine which currently acceptable amphoterics work for both formulation and performance of conditioner prototypes.

Lecithins, partially composed of diacyl glycerophospatatidyl choline, present an isoelectric point of about pH 6.7. Therefore, lecithins can act as a cationic surfactant in that moderately acid pH given the net negative charge of hair.¹¹ Much of the commercial food grade lecithin comes from genetically modified organism (GMO) soybean feed stock, but available sunflower and non-GMO soy products are available in both native unsaturated and hydrogenated forms. These are more oxidative-stable with a higher melt.

Restoring hair lipids: The primary lipid in hair has been identified as the chemically bound thioester 18-methyleicosanoic acid (18-MEA)—although it only superficially coats hair by weak hydrophobic dispersion forces, with deposition being enhanced with cationic surfactants.¹² Simple vegetable oils can supply some of the lipid stripped from the hair, and argan oil, a highly unsaturated triglyceride from the nuts of Argania spinosa, has become a popular variety of vegetable oil to replace 18-MEA. The stable liquid wax jojoba oil, i.e., fatty alcohol fatty acid ester, moringa oil and many other exotic oils are used with claims that note use by indigenous people for their benefits. These oils therefore fit various marketing stories but higher alkyl chain variants like Limnanthes alba (meadowfoam) with a preponderance of > C20 fatty acids, may get closer to replacing the natural 18-MEA.¹³ An early U.S. patent mixed coconut oil with Citrus aurantium (bitter orange) juice, capsicum oil and iodine for hair conditioning, so the admixture of natural oils has a long-standing tradition.¹⁴

Additional ingredients: Currently available auxiliary ingredients are useful for both structural composition and performance of natural conditioners. Simple hydrolyzed proteins and amino acids find utility in moisture retention and potential structural replacement of proteinaeceous material lost during chemical treatments. The vegetable protein sources used for these products are currently dictated by available food feedstocks. In the future, the cosmetic industry should proactively search for feedstocks that contain a mix of amino acids tailored to performance needs such as high cysteine content or more relative hydrophobicity. Of the common grain and seed proteins the cosmetic industry currently utilizes, wheat protein probably has the highest cysteine content (~ 2 mole %) compared to human hair’s approximate 14%.¹⁵ Protein selection might also be directed towards this more hydrophobic or lipophilic character, with the objective being proteins with better conditioning performance on the hair fiber. Choice of protein hydrolyzates might be determined by the relative content of amino acids with a greater Hydopathy Index, the measure of relative hydophobicity. In this scheme, higher values are given for aliphatic non-polar amino acids such as isoleucine and valine.¹⁶

Natural cationic polymers are not as readily available as the typical anionic, nonionic and amphoteric versions of carbohydrates and proteins. Chitosan, a natural cationic polymer containing glucosamine residues, is commercially available in shrimp shells, which may present an issue for companies that are reluctant to use an animal derived by-product.¹⁷ Chitin can be sourced from certain fungi, where it is present as a large component of their cell walls.¹⁸ As sources and variations in molecular weight become more available, chitin’s derivative chitosan should find wider use with its antibacterial and immune activating properties.

Future Directions

Beyond the formulation of more effective conditioners with currently available ingredients, future innovation will come from new materials discovered directly in nature or adapted from nature. Most current natural and organic standards allow the chemical processes esterification, hydrogenation, glucosidation and protein fragment acylation. Within that framework, the cosmetic industry can source naturally occurring small aliphatic nitrogen compounds for linking acyl/alkyl fatty groups to form esters and amides that have substantivity to hair fibers for conditioning properties. Examples previously discussed include the basic amino acid arginine and isoleucine in the brassica alcohol surfactant. A wide variety of other commercially available amino acids and protein fragments can be envisioned—including glucosamine (the backbone of chitin), its N-acetyl derivative (present in hyaluronic acid), choline and betaine. Panthenol, widely promoted as provitamin B5, is a precursor of the amide functional pantothenic acid, which is derived naturally from beta-alanine and may be potentially derived from another small water soluble nitrogenous natural that could be further modified for conditioning functionality.

The use of the naturally occurring cationic quaternary amino acid-derived carnitine, currently used as a nutritional supplement due to its involvement in fat metabolism, should also be investigated. Its derivatives have been used in diverse applications such as intracellular drug delivery, gene transfection and antimicrobial activity.^{19, 20} The future of natural conditioners looks promising in the short and long term with a combination of formulation and ingredient innovation.

References

1. A Georgalas, Formulating with Naturals—Hair Care, Cosmet & Toil 126(4) pp 250–255 (2011)
2. Conditioning needs for different hair types, ch 5.3.2 in Cosmetology, Theory and Practice, Vol II, K Schrader and A Domsch, eds, Verlag fur Chemische Industrie, H. Ziolkowsky GmbH: Augsburg, Germany (2005) pp 39–42
3. Key Ingredients, Sweet Almond Mint Conditioner, www.wenhaircare.com/whyitsunique.php (accessed Oct 17, 2012)
4. Joe Smillie, NSF/ANSI 305: Personal Care Products Containing Organic Ingredients, presentation at the Sustainable Cosmetics Summit, Organic Monitor UK, New York, USA (Mar 25, 2010)
5. US Pat 8,105,569, Non-petrochemically derived cationic emulsifiers that are neutralized amino acid esters and related compositions and methods, Rocco Burgo, assigned to Inolex Corp. (Jan 31, 2012)
6. E Oshimura and R Yumioka, Conditioning hair with amino acid derivatives: New amphoterics with associative actions with cationic surfactants, presentation at the 25th IFSCC Congress, Barcelona, Spain (2008)
7. E Oshimura, Hair and amino acids, chapter 37 in Naturals and Organics in Cosmetics: Trends and Technology, Allured Business Media: Carol Stream, IL USA (2010) pp 405
8. EG Lomax, Amphoteric Surfactants, 2nd Ed, CRC Press: Boca Raton, FL USA (1996) pp 121
9. CR Robbins, Interactions of Shampoo and Crème Rinse Ingredients with Human Hair, ch 5 in Chemical and Physical Behavior of Human Hair, Fourth Edition, Springer-Verlag: New York, USA (1988)
10. MJ Rosen, Characteristic features of surfactants, ch 1 in Surfactants and Interfacial Phenomena, Third Edition, John Wiley & Sons Inc.: Hoboken, NJ USA. (2004) pp 26-27
11. US Patent 5,002,761, Hair treatment compositions containing natural ingredients (lecithin), R Mueller, H Hoeffkes, K Seidel and K-D Wisotzki, assigned to Henkel (Mar 26, 1991)
12. H Tanamachi et al, Deposition of 18-MEA onto alkaline-color-treated weathered hair to form a persistent hydrophobicity, J Cosmet Sci 60 31–44 (January/February 2009)
13. AJ O’Lenick, Jr., AJ O’Lenick, DC Steinberg, K Klein and Carter LaVay, Oils of Nature, Allured Business Media: Carol Stream, IL USA (2008)
14. US Patent 3,824,304, Hair conditioner (coconut oil), AF Viuaneuva (Jul 16, 1974)
15. HD Belitz et al, Food Chemistry, 3rd ed, Springer-Verlag: Heidelberg, Germany (2004) pp 688
16. ZE Sikorsky, Chemical and Functional Properties of Food Proteins, CRC Press: Boca Raton, FL USA (2001) pp 40
17. Brockway and Hili, Formulating green personal care products, ch 5 in Sustainable Cosmetic Product Development, Wen Schroeder, ed, Allured Business Media: Carol Stream, IL USA (2011) pp 182
18. SM Bowman and SJ Free, The structure and synthesis of the fungal cell wall, BioEssays 28 799–808 (2006)
19. US Patent 7,585,519, Esters of L-carnitine or alkanoyl L-carnitines as cationiclipids for the intracellular delivery of pharmacologically active compounds, C Pisano, MO Tinti, M Santaniello, L Critelli and G Salvatori, assigned Sigma Tau Industrie Farmaceutische Riunite SpA (Sept 8, 2009)
20. US Patent 5,925,369, Bis alkanoyl esters of carnitine having antimicrobial, antifungal and antiprotozoal activity, F De Angelis, G Gramiccioli, N Scafetta and MO Tinti (July 20, 1999)