HAIR CARE
these ingredients have a long record of use in cosmetics – and they are perceived as ‘chemical’ by consumers and cannot be used in natural concepts. This gap triggered research in our labs several years ago, starting the search for a naturally-derived anti-dandruff active that should not be inferior in efficacy. Intensive studies have led to the optimisation of a class of ingredients well known for certain antimicrobial activity with good detergent properties. This dual activity distinguishes the acyl lactylates presented in this paper from commonly found chemical anti-dandruff agents. The newly-launched Dermosoft decalact (INCI: Sodium Caproyl/Lauryl Lactyl Lactate) shows excellent antimicrobial properties and at the same time outstanding foaming and foam stabilising properties. This, together with a high degree of substantivity as shown in a clinical study presented in this paper, makes Dermosoft decalact a very interesting and cost-effective natural anti-dandruff active.
Anti-microbial activity against Malassezia furfur It is well known among experts that the yeast, Malassezia furfur, is among the main factors for the development of dandruff. Therefore, besides removal of loose corneocytes and sebum control, the primary target for anti-dandruff products is the control of Malassezia furfur. There are a number of petrochemically derived antimicrobials that are used in anti-dandruff shampoos. During recent years, following a general tendency for milder ingredients, there has been an increased use of a newer ingredient, piroctone olamine, first used in 1979. Nevertheless, with piroctone olamine being of petrochemical origin and relatively expensive, there is a continuing demand for a natural active, as effective and if possible more economic than piroctone olamine. Further benefits of the alternative material should be ease of use, better solubility and the possibility of formulating transparent anti-dandruff shampoos. Furthermore, formulators should always attempt to adjust the pH of a product to the needs of the human skin – not to the active ingredient. The physiological pH of normal skin is just below pH 5.0. To maintain a healthy skin and scalp this pH should be stabilised and not altered by hair care products. While piroctone olamine needs a relatively high pH (around 7) for optimum performance, Dermosoft decalact has an excellent performance at the natural pH of the scalp and hair, between pH 4 and 5. In a process of optimisation of existing concepts with known efficacy against yeast- type microorganisms we developed a unique combination of lactylates that showed best performance in reducing Malassezia furfur. The reduction of the dandruff-causing yeast
112 PERSONAL CARE April 2012
Table 1: Solubility of anti-dandruff actives. Name of active
Dermosoft decalact
Solubility in water (pH 7, room temperature) ■ 1% SLES ■ 1% Dermosoft decalact ■ 0.5% SLES +O.5% Dermosoft decalact
20 18 16 14 12 10 8 6 4 2 0
>2%
Piroctone Zn-pyrithione Selenium olamine
0.05% 8 ppm
disulfide Insoluble
01
Time (min)
2
5
Figure 3: Foam stability of SLES compared to Dermosoft decalact and mixture of both. The total foam volume was placed in a graduated cylinder and the decomposition of the foam measured after 1, 2 and 5 minutes. Note the improved foam stability of SLES in combination with Dermosoft decalact.
was tested in vitro comparing with a benchmark active (piroctone olamine) and placebo. While in pure water, the efficacy of piroctone olamine and Dermosoft decalact (now referred to as ‘the natural anti-dandruff active’) is the same (total reduction of Malassezia furfur after three minutes) the performance in a shampoo formulation is different. The influence of the shampoo formulation on the efficacy of the two anti-dandruff agents is reflected in Figures 1 and 2. All samples were prepared using the same basic shampoo formulation based on SLES/cocamidopropylbetaine and using recommended dosage of the actives, tested first at a pH level of 5.3. The result of the in vitro tests shows a better reduction of the germ after for the natural anti-dandruff active compared to piroctone olamine, but no significant reduction for the placebo shampoo without any anti-dandruff active. This same test performed with shampoos at a lower pH (4.3) shows a much better performance of the natural anti-dandruff active, resulting in a complete reduction of the germ after 30 minutes with the natural anti-dandruff active, while the same formulation with piroctone olamine failed to reduce the germ completely even after six hours.
Problems formulating with conventional anti-dandruff actives Typical drawbacks of traditional anti- dandruff agents are the limited solubility and discolouration of the finished product.
The limited solubility of Zn-pyrithione or piroctone olamine makes it very difficult or impossible to obtain clear, transparent solutions. Being a lesser problem in hair treatments that are emulsion based, it is a major disadvantage for the formulation of shampoos or hair tonics. In such concepts it is often desired to offer a transparent product, since this opens more possibilities for the packaging and presentation of such a product to the consumer. However, even though piroctone olamine can yield transparent products in selected surfactant bases, it should not be displayed in transparent packaging due to its decomposition by exposure to daylight. Discolouration is another annoying area for manufacturers of anti-dandruff shampoos, but for the consumer too. Piroctone olamine forms a yellow coloured complex with traces of iron (1 ppm of iron being enough according to the technical data sheet of the supplier) and it cannot be avoided by using complexing agents. For other agents it is more of a concern for the consumer, as it is known for example that selenium disulfide shows discolouration of hair dyes and the hair itself, thus strongly interfering with the whole concept of hair care.
Regarding the ease of use, stability issues or discolouration, there are no drawbacks found for the natural anti- dandruff active. It shows good and sufficient solubility for allowing transparent products with an effective concentration. There is neither a colour change of the
Volume (cm3
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