Department of Microbiology, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand.
J Microbiol Biotechnol. 2020 Aug 28;30(8):1184-1194. doi: 10.4014/jmb.2003.03019.
Melanin is a major factor that darkens skin color as one of the defense systems to prevent the harmful effects of UV light. However, darkened skin from the localized or systemic accumulation of melanin is viewed in many cultures as an esthetic problem. Consequentially, searching for antimelanogenic agents from natural sources is very popular worldwide. Previous screening of fermented rice products, obtained from various rice cultivars fermented with different sources of loog-pang (Thai traditional fermentation starter), revealed that the highest ability to reduce the melanin content in B16F10 melanoma cells was from unpolished black rice fermented with a defined starter mixture of microbes isolated from loog-pang E11. The aim of this study was to investigate the mechanism of the fermented unpolished black rice (FUBR) on the inhibition of melanogenesis in B16F10 melanoma cells. The strongest reduction of cellular melanin content was found in the FUBR sap (FUBRS). The melanin reduction activity was consistent with the significant decrease in the intracellular tyrosinase activity. The FUBRS showed no cytotoxic effect to B16F10 melanoma or Hs68 human fibroblast cell lines. It also significantly reduced the transcript and protein expression levels of tyrosinase, tyrosinase-related protein 1 (TYRP-1), TYRP-2, and microphthalmia-associated transcription factor. Furthermore, it induced a significantly increased level of phosphorylated ERK, p38 and Akt signaling pathways, which likely contributed to the negative regulation of melanogenesis. From these results, a model for the mechanism of FUBRS on melanogenesis inhibition was proposed. Moreover, these results strongly suggested that FUBRS possesses antimelanogenesis activity with high potential for cosmeceutical application as a skin depigmenting agent.
黑色素是使皮肤颜色变深的主要因素之一，是防止紫外线伤害的防御系统之一。然而，在许多文化中，由于黑色素的局部或系统性积累导致的肤色变深被视为美学问题。因此，从天然来源中寻找抗黑色素生成剂在世界范围内非常流行。以前对发酵大米产品的筛选发现，从用不同来源的 loog-pang（泰国传统发酵启动剂）发酵的各种大米品种中获得的发酵大米产品，具有最高能力降低 B16F10 黑色素瘤细胞中的黑色素含量来自用从 loog-pang E11 中分离出的微生物定义的起始混合物发酵的未抛光黑米。本研究的目的是研究发酵未抛光黑米（FUBR）对 B16F10 黑色素瘤细胞中黑色素生成抑制的作用机制。在 FUBR 汁（FUBRS）中发现细胞内黑色素含量降低最强。黑色素还原活性与细胞内酪氨酸酶活性的显著降低一致。FUBRS 对 B16F10 黑色素瘤或 Hs68 人成纤维细胞系没有细胞毒性作用。它还显著降低了酪氨酸酶、酪氨酸酶相关蛋白 1（TYRP-1）、TYRP-2 和小眼畸形相关转录因子的转录和蛋白表达水平。此外，它诱导显著增加的磷酸化 ERK、p38 和 Akt 信号通路水平，这可能有助于黑色素生成的负调控。根据这些结果，提出了 FUBRS 抑制黑色素生成作用机制的模型。此外，这些结果强烈表明 FUBRS 具有很强的抗黑色素生成活性，具有作为皮肤美白剂的美容应用潜力。
