Photochemical reaction to increase melanogenesis using Buddleja officinalis and blue light-emitting diode irradiation in B16F10

• 15 natural products were screened as photosensirizer. • Blue light irradiation was used together with Buddleja officinalis extract, melanin synthesis and TYR activity were increased. • Buddleja officinalis extract with blue light irradiation can induce intracellular melanin content. • Melanosome transport was promoted by BO-IR and increased expression of genes related to melanin production. Recently, the incidence of vitiligo has increased because of stresses induced by external environment. Ultraviolet (UV) light therapy is the most commonly used method of treating the disease; however, UV light therapy requires a long treatment period, and prolonged exposure to UV radiation has side effects. The purpose of the present study was to investigate the effects of natural products and LED irradiation (LED-IR) on the synthesis of melanin. It was not possible to effectively increase intracellular melanin production through individual applications of Buddleja officinalis (BO), which is a natural substance selected through screening, or blue light irradiation (Blue-IR). However, when used in combination, these two agents stimulated adenylyl cyclase (AC) and melanin production was induced in the stimulated cells via the CREB/MITF/TYR pathway. Furthermore, the combined treatment with BO and Blue-IR generated low levels of cellular reactive oxygen species (ROS) and induced p38 phosphorylation, which in turn activated MITF in ROS-stimulated synthetic melanocytes, resulting in the promotion of melanogenic pathways other than the CREB/MITF/TYR pathway. In addition, this treatment combination effected melanin transport. These results suggested that the combined therapies can be used to treat melanin-deficiency skin diseases such as vitiligo.