The stabilising effect of met[h]ylsulfonylmethane (MSM) on urea containing formulations
Botha, Johanna Margaretha
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The skin is the largest area of the body that interfaces with bacteria and "problems" from the environment and is the first line of defence for the body. There are, of course, immune system functions that take place within the skin area and it would be nourished only by the very small arteries (capillaries). So the blood supply at the surface of the skin is not as great as it is further inside the body. When you can apply something on the skin, which nourishes the immune system cells, such as MSM (methylsulfonylmethane) and urea you are doing wonders in improving the health of the skin. The use of urea in dermatological therapy and cosmetics has become more and more important in recent years. However, urea is unstable in formulations, decomposing into carbon dioxide and ammonia. Products containing urea can be stabilised by including MSM (methylsulfonylmethane) in the formulation (Herschler, 1981:l). The aim of this study was to determine the stabilising effect of MSM on urea in cosmetic products. Cosmetic products that were formulated with MSM and urea as actives, comprised of a moisturising lotion, massage cream, foot and heel balm, hair gel, hair spray and lip ice. The formulations were subjected to stability studies for three months under ICH conditions. The formulated products were stored at 5ºC, 25ºC/60%RH and 4OºC/75%RH. The strength of MSM and urea in each formulation was 5% m/m , except for the hair spray and lip ice where the concentrations were 10% m/m and 2.5% m/m respectively. HPLC analysis was used to determine the urea concentrations in all the formulated products, as well as the concentration released during membrane release studies. GC analysis was used to determine the MSM concentrations in the products. Other stability tests included appearance, spreadability, pH, relative density, penetration, viscosity, preservative content and preservative efficacy. Chapter 1 gives a literature overview of the uses and importance of cosmetics. Chapter 2 is a literature overview of the skin and the properties and uses of urea and MSM. Chapter 3 deals with the formulation of urea and MSM products and the chemicals that have been used. Chapter 4 described the methods used for accelerated stability testing. Chapter 5-10 finally deals with the results obtained and the conclusions that were made. The test results showed the following: There was a prominent change in the pH of all the formulated products; this can be due to decomposition of urea into carbon dioxide and ammonia (Beiersdorf, 2003: 1). Higher temperature and moisture increase this decomposition and cause the pH to increase to values as high as 11 (Anon, 2003:20). The viscosity, spreadability, penetration, relative density and appearance of the products remained more or less the same over three months, except for the hair spray where crystals formed in the product that was stored at 5ºC for 1 month due to the menthol in the formulation. The urea and MSM content decreased with time. The lip ice formulation showed concentrations as low as 30% due to poor solubility of the urea and MSM crystals in the waxes of the lip ice formulation. HPLC analysis of the preservatives confirmed their stability in the formulated products. The preservative efficacy results proved that the products were sufficiently protected from microbial contamination. The release study indicated that urea is released at a steady rate from the preparations tested. Urea was released from the moisturising lotion after 120 minutes. In general, the release is influenced by the viscosity of the medium and should be faster from the gel than from the creams or lotion (Shah et al., 199155). In conclusion it can be said that urea and MSM were successfully formulated into the six cosmetic products except for the lip ice, which showed low, unstable concentrations of the actives due to poor solubility of the actives in the waxes of the lip ice formulation. By comparing the results of Claasen, (2003:63) and the results obtained in this study for the hair gel and foot and heel balm, it looks as if MSM had a stabilising effect on urea, by lowering the decrease of urea concentrations over time.
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