Kao Corporation, R&D - Hair Care Products Research, Tokyo 131-8501, Japan.
Department of Chemistry, Fujita Health University School of Medical Sciences, Toyoake, Aichi 470-1192, Japan.
Int J Mol Sci. 2019 Jul 31;20(15):3739. doi: 10.3390/ijms20153739.
In a previous study, we showed that the size of melanosomes isolated from Japanese female hairs enlarges with age, and this affects the hair color. In this study, we analyzed the age-dependent changes in hair melanin in order to further explore the factors related to hair color changing by aging. A significant positive correlation with age was found in the total melanin amount (TM) and the mol% of 5,6-dihydroxyindole (DHI) units, while no correlation was found in pheomelanin mol%. TM showed significant correlations with hair color parameters and the melanosome volume, suggesting that hair color darkening by aging is caused by the increase in TM due to the enlargement of the size of melanosome. From the measurement of absorbance spectra on synthetic eumelanins with different ratios of DHI and 5,6-dihydroxyindole-2-carboxylic acid (DHICA), we found that the increase in DHI mol% also contributes to the darkening of hair color by aging. In addition, the level of pyrrole-2,3-dicarboxylic acid (PDCA), a marker of DHI melanin, showed a significant negative correlation with the aspect ratio of melanosome, suggesting a contribution of DHI melanin to the change in melanosome morphology by aging.
在之前的一项研究中，我们表明从日本女性头发中分离的黑素小体的大小会随年龄增长而增大，这会影响头发的颜色。在这项研究中，我们分析了毛发黑色素随年龄的变化，以进一步探讨与衰老导致头发颜色变化相关的因素。总黑色素量（TM）和 5,6-二羟基吲哚（DHI）单位的摩尔%与年龄呈显著正相关，而真黑色素摩尔%与年龄无相关性。TM 与头发颜色参数和黑素体体积呈显著相关，表明由于黑素体体积增大导致 TM 增加，从而导致头发颜色随年龄增长而加深。从不同 DHI 和 5,6-二羟基吲哚-2-羧酸（DHICA）比例的合成真黑素的吸收光谱测量中，我们发现 DHI 摩尔%的增加也有助于头发颜色随年龄增长而加深。此外，吡咯-2,3-二羧酸（PDCA）的水平，即 DHI 黑色素的标志物，与黑素体的纵横比呈显著负相关，表明 DHI 黑色素对黑素体形态随年龄变化的贡献。
