The intracluster ion-molecule reactions occurring within the titanium/methanol heterocluster ions are studied using a simple cluster source based on the mixing of the laser-ablated plasma with the supersonic expansion of a methanol vapor seeded in Ar carrier gas. The product ions are detected using a reflectron time-of-flight mass spectrometer. The mass spectra exhibit a major sequence of cluster ions with the formula Ti + (CH 3 O) 2 (CH 3 -OH) n , which are attributed to the hydrogen elimination reactions (-2H or -H 2 ) of Ti + ion within the heteroclusters. In addition, heterocluster ions of the types Ti + (CH 3 O)(CH 3 OH) n and Ti + (CH 3 O) 3 (CH 3 OH) n also emerge throughout the observed mass spectra, indicating that consecutive H-eliminations by the Ti + ion occur for up to three methanol molecules. The results from isotope-labeling experiments suggest that H-elimination is the reaction path for O-H bond breaking in Ti + -methanol heteroclusters. The observed TiOH + and TiO + ions are interpreted as arising from the insertion of Ti + ions into the C-O bond in CH 3 OH, followed by CH 3 -and CH 4 -elimination, respectively, from the [HO-Ti + -CH 3 ] intermediate. The experiments also show that the chemical reactivity of heterocluster ions is greatly influenced by cluster size and argon stagnation pressure. The reaction energetics and formation mechanisms of the observed heterocluster ions are also discussed.

Miconazole (MIC), a regional antifungal agent, has been used worldwide in the treatment of superficial mycosis. However, the effect of MIC on skin pigmentation is not known. In this study, we investigated the inhibitory effect of MIC on melanogenesis in B16 melanoma cells. Tyrosinase activity and melanin content were dose dependently decreased by MIC as compared with untreated cells. The level of tyrosinase protein expression was reduced with treatment MIC. A decrease in cell proliferation was observed in B16 cells treated with MIC 30 m mM, indicating that the MIC-induced depigmenting effect was caused by inhibition of melanin synthesis and not by destruction of B16 cells. Furthermore, MIC markedly suppressed a a-melanocyte stimulating hormone or forskolin-induced tyrosinase activity in B16 cells. Therefore the depigmenting effect of MIC might be due to the inhibition of tyrosinase activity and tyrosinase expression, which eventually slows melanin biosynthesis. These results indicate that MIC may be a useful inhibitor of melanogenesis in B16 cells and suggest that it may have beneficial effects in the treatment of hyperpigmentation disorders such as ephelis and melasma.

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Skin diseases are a hyperpigmentation, hypopigmentation and melanoma, etc. Among them, recent studies have focused on the hyperpigmentation, which is especially abnormally increased colorations or spots. Hyperpigmentation such as chloasma, coloration or freckles increased abnormally the amount of melanin in the epidermis. [1][2][3][4][5] Some of the principle causes of hyperpigmentation are exposured to ultraviolet light, genetic reasons, metabolism, inflammation, infection, the endocrine system and reminded scars. [6][7][8] Melanin is synthesized in melanosomes of the melanocyte. The formed melanin granules are moved from the melanocytes cytoplasmic extensions to keratinocytes. 9,10) The melanocytes produce melanin by a process that involves the transformation of tyrosine into 3,4-dihydroxyphenylalanine (DOPA) by the enzyme tyrosinase and the subsequent transformation of DOPA into melanin. 5,11,12) Tyrosinase is the key enzyme in the pathway of melanogenesis. Tyrosinase plays a regulatory role in the production of melanin.13-15) Accordingly, the regulation of tyrosinase may not only control melanin production but also develop new therapy for pigmentation. Pharmaceutical agents which control melanin production or melanin metabolism are used as whitening agents. A number of whitening compounds have been screened for their effectiveness in reducing melanogenesis. 16)Radix Trichosanthis (RT) is the dry roots of Trichosanthis kirilowii MAXIM. (Cucurbitaceae) collected in the spring and fall. It is used in traditional Chinese medicine as an antiphlogistic, antifebrile, and cough remedy. It was also found to be effective as an abortifacient.17) It was found that the active principle of RT is a basic protein named trichosanthin.18) Recently, we have demonstrated that the water extracts of RT dose-dependently inhibit melanin synthesis and also abrogate cAMP-induced melanogenesis in B16 cells, but develops cytotoxicity.19) Thus, it would be important to abrogate the deleterious effects of RT using agents with a more physiological action.Radix Ginseng (RG) is the dry root of Panax ginseng C.A. MEY. (Araliaceae), a worldwide well-known traditional Chinese medicine with the popular name "ginseng". The wildgrowing or cultivated ginseng root is collected in the fall and used as a tonic.20) The major constituents of ginseng are the saponins, which include 30 kinds of ginsenoside. 21,22) Recently, it has been shown that panaxadiol fraction and its ginsenosides could induce the antioxidant enzymes, such as superoxide dismutase and catalase, which are important for maintaining cell viability.23) Also RG possess adaptogen-like effect to foreign deleterious infringement. 24) In view of the above reports, it can be considered that RG inhibits the cytotoxicity caused by RT.Therefore, the present study was conducted to investigate the effects of RG and RT on the melanogenesis in B16 melanoma cells. MATERIALS AND METHODS Sample and Preparation of ExtractRT and RG were standardized articles of the Korean pharmacopoeia (KP). The extracts...

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