LIPO-AMINO ACID CHOLESTERYL DERIVATIVES 355 Osborne (17). Fatty acids were first mixed and partially (41%) neutralized by the addition of an aqueous NaOH solution. Total water content in each model was adjusted to 25 wt. %. CHARACTERIZATION OF THE STRATUM CORNEUM LIPID In order to form a lamellar structure, models with deionized water were heated to about 80øC and allowed to cool to room temperature (25øC). This heating and cooling process was repeated several times, and the resulting structure was observed using a polarizing microscope and small-angle x-ray diffractometry (Cu-Kot radiation). RESULTS RECOVERY EFFECT OF CHOLESTERYL DERIVATIVES FOR DAMAGED SKIN After a 24-hour closed patch with 1 wt % SLS, the volar side of the forearm showed O o o 40 30' 20' 10' mean_+S.E. O I I I ' I ' I -1 0 1 2 3 days after application = blank ,i, AGCE-301 ß *, AGCE-202 [] Petrolatum - Cholesteryl Hydroxystearate Figure 2. Water-holding capacity following application of cholesteryl derivatives.

356 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS E LM 15 mean_S.E. 0 ' I ' I ' I ' I ' I ' -2 -1 0 1 2 3 4 days after application = blank •' AGCE-301 ß *' AGCE-202 []-- Petrolatum - Cholesteryl Hydroxystearate Figure 3. TEWL recovery following application of cholesteryl derivatives. well-defined erythema with an average dermal score of 3 (Figure 1). Application of petrolatum produced significant recovery compared to the sites without sample appli- cation as a control (day 3 p 0.05). Compared to petrolatum, AGCEs showed remark- ably quick recovery (days 2,3 p 0.05). Although AGCEs tended to reduce the dermal scores more than cholesteryl hydroxy stearate, the difference in the recovery effect was not significant. Figure 2 shows changes in the water-holding capacity of damaged skin. When left untreated, the water-holding capacity remained at a low level for three days. In contrast, application of any sample consistently induced recovery in the water-holding capacity. The water-holding capacity of stratum corneum treated with AGCE-202 was signifi- cantly greater than that with cholesteryl hydroxy stearate (days 1,2,3 p 0.05) or petrolatum (day 3 p 0.02). TEWL increased significantly in SLS-induced damaged skin (Figure 3). Compared to