Lipids are important constituents of the human epidermis. Either free and organized into broad lipid bilayers in the intercorneocytes spaces, or covalently bound to the corneocyte envelope, they play a crucial role in permeability barrier function and are major contributors to cutaneous anti-microbial defense. Free sphingoid bases are a recent addition to this family of active lipids, which emerged from studies of breakdown products from ceramides. Phytosphingosine (PS) is a lipid occurring naturally in the stratum corneum, both in its free form and as a part of the major fraction of ceramides. The biotechnological production of PS patented by Degussa yields to PS with the correct configuration present in the skin. So, application of a PS containing formulation leads to its integration into the natural lipid structures of the skin. In acne, different pathogenetic factors contribute to the inflammation process, defect in keratinization, increased sebaceous gland activity and increased colonization of Propionibacterium acnes. The results of in vitro and in vivo studies confirm the previous reports on strong anti-microbial effectiveness of skin-identical PS produced by Degussa in vitro and in vivo. In addition, PS shows excellent clinical results in the context of skin care in acne, based on both anti-inflammatory and anti-microbial activity. These results demonstrate the potential of PS to enhance or complement existing acne therapies acting as an active cosmetic ingredient.

Many analytical methods are used to measure the antioxidative activity of substances yet little is known about the comparability of the test results between laboratories. After an initial evaluation of a broad range of methods conducted by one laboratory, the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, the trolox equivalent antioxidant capacity (TEAC) assay, the lipid assay (or 2,2'-azobis(2-aminepropane) (ABAP) assay) and the thiobarbituric acid (TBA) assay were selected to be evaluated in the interlaboratory study. The antioxidative potentials of trolox, tocopherol, lipochroman-6, ascorbic acid, 4-methyl-brenzcatechin, and/or 3,5-di-tert-butyl-4-hydroxytoluene (BHT) were assessed using each of the methods. These methods were then evaluated in respect of their reproducibility and classification properties. Based on the results of this study, the DPPH assay followed by the TEAC assay yielded the best results based on reproducibility and sensitivity both within one laboratory and between laboratories. The results of the interlaboratory study were then compared with the single center results obtained from the commercially available photochemolumiescence (PCL) kit. To assess the transferability of chemical data to biological systems, they were also compared with the single center results obtained using the cell-based Dichlorodihydrofluoresceine (DCFH) assay.

In recent years the importance of sphingolipids (cerebrosides, sphingomyelin, ceramides, sphingosine-1-phospate, etc.) in skin biology is receiving an increasing interest. Not only are ceramides essential for the barrier function of the skin, especially through their phytosphingosine, sphingosine and 6-hydroxysphingosine derivatives, they are now also known to be cell-signalling mediators which can improve epidermal differentiation. However, their effects on dermal anti-ageing markers and reduction of wrinkles have not been established. In this study, we were interested in the effects of a sphingolipid derivative, salicyloyl-phytosphingosine (SP), because of the known independent beneficial effects of salicylic acid and phytosphingosine on skin. Both of these agents are known to reduce the activities of the activator protein-1 transcription factor, in a manner similar to that observed with retinoic acid (RA) treatment. Through this mechanism, RA was shown to reduce the levels of matrix metalloproteases (MMPs) and the increase levels of extracellular matrix proteins. Therefore, we examined the effects of SP on procollagen-I synthesis in fibroblasts in vitro, its effects in vivo on the expression of dermal markers such as fibrillin-1, procollagen-I and MMP-1 immunochemically in biopsies taken from a short-term occluded patch test protocol and, its effects on periorbital wrinkle reduction over 4 weeks using Fast Optical In Vivo Topometry of Human Skin. In vitro we observed a significant increase in the production of procollagen-I by adult human fibroblasts (two fold increase, P < 0.01) which encouraged us to test the effects of SP in vivo. Initially, test products (SP at 0.05% and 0.2%, all-trans RA (0.025%) and vehicle were applied under occlusion for 8 days prior to biopsy and histological assessment in photoaged volunteers (n = 5). Increased deposition of fibrillin-1 and procollagen-I, together with reductions in the levels of MMP-1, were observed for the SP treatments (P < 0.05). Similar effects were observed for RA, except for the increases in procollagen-I. With these beneficial effects on the basement membrane and papillary dermal markers, we evaluated the effects of SP in an oil-in-water (O/W) cream for its effects in reducing the appearance of periorbital wrinkles in a 4-week, half-face clinical study compared to placebo cream (moderately photoaged female subjects aged 41-69 years; n = 30). Clear reductions in wrinkle depth and Rz (skin smoothness) together with Ra (skin roughness) parameters were observed (P < 0.05), indicating an anti-wrinkle benefit. In conclusion, this series of studies demonstrated for the first time that a ceramide derivative, such as that SP, was a novel agent for the repair of photoaged skin and highlight its effects at the cellular, tissue and organ levels.