Phytosphingosine for Skin Differentiation and Other Topics: Literature Findings

By: Charles Fox, Independent Consultant

Posted: December 1, 2009, from the December 2009 issue of Cosmetics & Toiletries.

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Composition A contained 21.67 g polyoxyethylene sorbitan monolaurate, 11 g silica and a balance to 100 g of a mineral oil. Composition B contained an aqueous solution of 40% w/w monoethanolamine. Thus, nine parts of A was mixed with one part of B and 10 parts of an aqueous solution of 6% hydrogen peroxide. The resulting composition, which had a pH of 10, was applied to the hair. Air-oxidative hair dye agent: Kao Corp. has disclosed air-oxidative hair dye agents to improve the coloring of gray hair as well as dye storage stability.¹²

The air-oxidative agent is characterized by containing: 5,6-dihydroxyindole and 5,6-dihydroxyindole-2-carboxylic acid or a salt thereof; an alkanolamine; L-ascorbic acid or its salt; a sulfite; and water, and could further contain a water-soluble or water-dispersible synthetic polymer. The agent had a pH between 10–11 at 25°C. An aerosol-type, air-oxidative hair dye agent filled in a pressure-resistant container with a propellant and a method for producing the hair dye agent are also disclosed. An example is shown in Formula 3.

Sunscreen Testing
Measurement of SPF in vitro: Miura et al. have published an algorithm for the in vitro determination of sun protection factors (SPF) based on a transmission spectrum measurement with the concomitant evaluation of photostability.¹³ During in vitro evaluations for SPF, the photostability of UV filters can have a major impact, especially for high SPF formulations; however, this is generally not taken into consideration. The described study presents a UV transmission spectrum measurement system utilizing a high-sensitivity UV photomultiplier tube with concomitant evaluation of photostability.

The researchers developed an algorithm to establish SPF in vitro by converting the amount of UV light transmission through the sunscreen layer into cumulative relative erythema effectiveness to obtain one minimal erythema dose. Thus, the algorithm uses the same endpoint as in vivo SPF methods but with a photomultiplier tube as the detector instead of skin. The values obtained showed excellent correlation with in vivo SPF values, even for high SPF sunscreens exceeding SPF 50. This method should be suitable as an in vitro SPF testing method.

Interesting Raw Materials and Vehicles
Silicone resin waxes: Shoji has published a review on a family of high performance silicone resin waxes.¹⁴ These materials are based on a linear model similar to polydimethylsiloxane; however, longer chain alkyl groups replace some of the methyl groups. Specifically, in this work, new molecules were synthesized by replacing the linear silicone chain in the alkyl siloxane with a propyl silsesquioxane resin. This resin is a branched structure end-capped with longer chain alkyl groups.