Hiroharu Shibayama

Permeation and metabolism of a novel ascorbic acid derivative, disodium isostearyl 2-O-L-ascorbyl phosphate, in human living skin equivalent models.

A novel amphiphilic vitamin C (VC) derivative, disodium isostearyl 2-O-L-ascorbyl phosphate (VCP-IS-2Na), which possesses a C18 alkyl chain attached to a stable ascorbate derivative, sodium L-ascorbic acid 2-phosphate (VCP-Na), was evaluated as a topical prodrug of VC with transdermal activity in human living skin equivalent (LSE) models. The permeation assay used was EPI-606X in the Franz-type diffusion cell system. VCP-IS-2Na exhibited much better permeability than VC and VCP-Na. The accumulation assays applied were EPI-200X and LSE-high by the dynamic system. The increased skin accumulation of VCP-IS-2Na was superior to that of VCP-Na and VC. VCP-IS-2Na that is susceptible to enzymatic hydrolysis by esterase and/or phosphatase released VC in the skin. Measurement of the metabolites that permeated and accumulated from the skin model suggested that VCP-IS-2Na was mainly metabolized via VCP-Na to VC in EPI-606X and EPI-200X, while it was mainly metabolized directly to VC in TESTSKIN LSE-high. Thus, these characteristics indicate that the novel VC derivative, VCP-IS-2Na, may be advantageous as a readily available source of VC for skin care applications.

Effect of a Novel Ascorbic Derivative, Disodium Isostearyl 2-O-L-Ascorbyl Phosphate, on Normal Human Dermal Fibroblasts against Reactive Oxygen Species

The novel amphiphilic vitamin C derivative disodium isostearyl 2-O-L-ascorbyl phosphate (VCP-IS-2Na), which has a C18 alkyl chain attached to the stable ascorbate derivative sodium L-ascorbic acid 2-phosphate (VCP-Na), was evaluated for reduction of cell damage induced by oxidative stress, ultraviolet A (UVA), ultraviolet B (UVB), and H2O2; stimulation of collagen synthesis against UVA irradiation; and inhibition of matrix metalloproteinase-1 (MMP-1) activity induced by UVA in human normal dermal fibroblasts. VCP-IS-2Na pretreatment resulted in significant protection against cell damage induced by UVB, UVA, and H2O2. The amount of type I collagen following UVA irradiation was increased by treatment with VCP-IS-2Na in a concentration-dependent manner. These effects of VCP-IS-2Na were superior to those of L-ascorbic acid (vitamin C, VC) and VCP-Na. On the other hand, VCP-IS-2Na suppressed 65% of the excess MMP-1 irradiated UVA, and VC and VCP-Na slightly suppressed it.

In vitro eye irritancy test of lauryl derivatives using the reconstructed rabbit corneal epithelium model

The rabbit corneal epithelium model (RCE model) was developed as a three-dimensional in vitro model to replace animal testing for the assessment of eye tolerance. In the model, a stratified culture of rabbit corneal epithelial cells is grown at the air-liquid interface on an amniotic membrane acting as a parabasal membrane. The alkaline exposure was restored each day in the presence of no irritants, although with the addition of SLS, which is a major irritant, the restoration of deficit was inhibited on the RCE model in a dose-dependent manner. The results of this test were comparable with those of the Draize test, and thus, this method using the RCE model may prove to be a useful and sensitive in vitro eye irritation test. The lauryl fatty chain derivatives, such as polyoxyethylene (9) lauryl ether (PLE), sodium polyoxyethylene (2) lauryl ether sulfate (SPLE), mono glyceryl laurate (MGL), and sodium N-lauroyl-l-glutaminate (SLG), which are widely used as surfactants for toiletry products and cosmetics, were evaluated for in vitro eye irritation potential using the RCE model. SLS, PLE, SPLE, MGL, and SLG inhibited 88.7%, 59.2%, 69.0%, 47.5%, and 15.7% of the restoration of deletion 24h after treatment at a concentration of 0.05%. The IC(50) (50% inhibitory concentration) values of SLS, PLE, SPLE, MGL, and SLG were 0.002%, 0.021%, 0.005%, 0.056%, and 0.448%, respectively. These results indicated that a functional group at the end of lauryl chain is an important factor for inhibiting the restoration of deletion using the RCE model.

Inhibitory effects of phytoncide solution on melanin biosynthesis.

To determine the component-activity relationships of phytoncide solutions on inhibitory activity in melanin biosynthesis, four types of phytoncide solution (A-type, AB-type, D-type, and G-type) were evaluated for inhibition of mushroom tyrosinase activity and melanin synthesis on murine B-16 melanoma cells and a human reconstituted skin model. The A-type, AB-type, D-type, and G-type of phytoncide solution treatment resulted in significant inhibition of tyrosinase activity. The amount of melanin was increased by treatment with phytoncide solutions in a concentration-dependent manner on murine B-16 melanoma cells without affecting cell growth. Furthermore, phytoncide solutions also suppressed melanin synthesis in a concentration-dependent manner on a human reconstituted skin model. These effects of A-type solution were superior to those of other solutions.