Antimelanogenic activity of hydrocoumarins in cultured normal human melanocytes by stimulating intracellular glutathione synthesis.

The antimelanogenic activity of six hydrocoumarins and alpha-tocopherol (alpha-Toc) in normal human melanocytes was evaluated in both cell culture systems and cell homogenates. The inhibitory effects of hydrocoumarins depended upon their substituent groups. alpha-Toc and some of the hydrocoumarins inhibited melanogenesis in cultured normal human melanocytes, although they did not influence melanin synthesis in enzyme solution prepared as cell homogenates. In addition, alpha-Toc and the hydrocoumarins stimulated intracellular glutathione (GSH) synthesis. In particular, 7-allyl-6-hydroxy-4,4,5,8-tetramethylhydrocoumarin strongly inhibited melanogenesis and intracellular GSH synthesis in normal human melanocytes, more so than alpha-Toc. Furthermore, hydrocoumarins exhibited higher scavenging and quenching activities against with tert-butyl peroxyl radicals and singlet oxygen species. These results suggest that 7-allyl-6-hydroxy-4,4,5,8-tetramethyl hydrocoumarin would be useful as an antimelanogenic agent for the prevention or improvement of skin pigmentation induced by reactive oxygen compounds and free radicals, and may inhibit melanogenesis, including tyrosinase transfer and melanosome differentiation, by interrupting melanization by increasing the intracellular GSH content.

Relationship between geomorphological land classification and soil amplification ratio based on JMA strong motion records

The relarionship between the soil amplification ratio and ground conditions was examined using strong motion records measured at 77 Japan Meteorological Agency (JMA) stations over a period of more than 8 years. The amplification ratios for the instrumental JMA intensity, as well as for the peak ground acceleration and velocity, were obtained from the station coefficients of the attenuation relationships. A combined use of geomorphological land classification and subsurface geology was found to yield the best estimate of the amplification ratio. This result suggests that the Digital National Land Information may be conveniently used for the estimation of strong motion distribution over large areas in Japan.(AU)