前田憲寿1), 井上東彦2), 西川洋史3), 三木聡子4), 漆畑 修4), 三木徳太郎3), 畑尾正人1)
Involvement of Melanin Monomers in the Skin Persistent UVA-Pigmentation and Effectiveness of Vitamin C Ethyl on UVA-Pigmentation
Kazuhisa Maeda1), Yoshihiko Inoue2), Masato Hatao1), Hiroshi Nishikawa3), Tokutaro Miki3), Satoko Miki4), Osamu Urushibata4)
We have discovered that melanin, which is dark brown in color and is a well-known cause of pigment spots and freckles, can also be produced outside of melanocytes (pigment-producing cells) by ultraviolet (UV) A radiation. Melanin is usually produced in melanocytes; however, this research proved that colorless melanin monomers (melanin precursors) accumulating in the basal layer of the epidermis, outside of melanocytes, turn into melanin by direct exposure to UVA radiation, and the brownish pigmentation remains in skin exposed to high doses of UVA for several weeks. Melanin is produced from one of the amino acids called tyrosine as a starting material through various premelanins. We conducted in vitro and in vivo experiments and found that 5, 6-dihydroxyindole-2-carboxylic acid (DHICA) and 6-hydroxy-5-methoxyindole-2-carboxylic acid (6H5MICA) accumulate in the keratinocytes and supernatants co-cultured with melanocytes, and readily respond to UVA to produce brownish melanin. We developed an in vitro and in situ method to evaluate ingredients, which inhibit melanization of DHICA and 6H5MICA caused by UVA radiation. We found that vitamin C ethyl (ethyl ascorbic acid) is an effective ingredient to inhibit the pigment formation from DHICA and 6H5MICA, and to prevent pigmentation of the basal layer of the epidermis caused by UVA. Clinical study proved that the effectiveness of vitamin C ethyl on UVA-induce persistent pigmentation. Making use of this technology, we have promoted the development of whitening skincare products.
ethyl ascorbic acid, DHICA, 6H 5 MICA, melanin, UVA
1)（株）資生堂 基盤研究本部 ライフサイエンス研究センター 薬剤開発研究所
Life Science Research Center, Basic Research Division, Shiseido Co. Ltd
2)（株）資生堂 製品研究本部 製品開発センタースキンケア製品研究所
Skincare Product Development Center,Product Development Division, Shiseido Co. Ltd
Nippon Hypox Laboratories, Inc.
2nd Department of Dermatology, Toho University School of Medicine
日本香粧品学会誌 Vol.27, No.4, pp.247-256 (2003)
上原 静香*，水谷 友紀*，中出 正人*，坂田 修*，佐々木一郎*，荒金 久美*，鈴木 正志*，内田理一郎**，徳武 昌一**
Inhibitory Effects of Proanthocyanidin-rich Extract from Grape Seeds on Melanogenesis
Shizuka UEHARA*, Yuki MIZUTANI*， Masato NAKADE*, Osamu SAKATA*， Ichiro SASAKI*， Kumi ARAKANE *,
Tadashi SUZUKI *， Riichiro UCHIDA **， Shoichi TOKUTAKE**
We investigated the inhibitory effect of proanthocyanidin-rich extract from grape seeds (PA) on melanogenesis. PA inactivated tyrosinase isolated from mushroom and dose-dependently reduced melanin production and tyrosinase activity in B16 mouse melanoma cells with no change in cell viability. PA did not have effect on the protein amounts and the level of mRNA of tyrosinase in normal human melanocyte, indicating that PA prevented melanin synthesis by inhibiting the tyrosinase activity selectively. Analysis of PA's proanthocyanidin by MALDI-TOF-MS revealed that PA was constituted by 1-13 units of catechin which was partly esterified with gallic acid. A comparison of the inhibitory effect of separated proanthocyanidin polymer on tyrosinase isolated mushroom indicated that the higher the unit of proanthocyanidin monomer (catechin), the stronger the proanthocyanidin inhibits tyrosinase activity. In the experiment of B16 mouse melanoma cells, lower degrees of polymerization of proanthocyanidins did not reduce melanin production and tyrosinase activity and the more than 3 degrees of polymerization reduced melanin production and tyrosinase activity in proportion to the degree of polymerization. Topical application of 1% PA cream effectively suppressed UV-induced hyperpigmentation in human. We concluded that the mechanism of melanogenesis-inhibitory effect of PA was due to selective inhibition of tyrosinase activity, and the higher degrees of polymerization of proanthocyanidins were more effective to reduce melanogenesis.
melanin, tyrosinase, melanogenesis, proanthocyanidin, MALDI-TOF-MS.
Research and Development Division, KOSÉ Corporation
Research and Development Division, Kikkoman Corporation