Protocatechuic Aldehyde Inhibits α-MSH-Induced Melanogenesis in B16F10 Melanoma Cells via PKA/CREB-Associated MITF Downregulation

Protocatechuic aldehyde (PA) is a naturally occurring phenolic compound that is a potent inhibitor of mushroom tyrosinase. However, the molecular mechanisms of the anti-melanogenesis activity of PA have not yet been reported. The aim of the current study was to clarify the melanogenesis inhibitory effects of PA and its molecular mechanisms in murine melanoma cells (B16F10). We first predicted the 3D structure of tyrosinase and used a molecular docking algorithm to simulate binding between tyrosinase and PA. These molecular modeling studies calculated a binding energy of −527.42 kcal/mol and indicated that PA interacts with Cu400 and 401, Val283, and His263. Furthermore, PA significantly decreased α-MSH-induced intracellular tyrosinase activity and melanin content in a dose-dependent manner. PA also inhibited key melanogenic proteins such as tyrosinase, tyrosinase-related protein 1 (TRP-1), and TRP-2 in α-MSH-stimulated B16F10 cells. In addition, PA decreased MITF expression levels by inhibiting phosphorylation of cAMP response element-binding protein (CREB) and cAMP-dependent protein kinase A (PKA). These results demonstrate that PA can effectively suppress melanin synthesis in melanoma cells. Taken together, our results show that PA could serve as a potential inhibitor of melanogenesis, and hence could be explored as a possible skin-lightening agent.     

Depigmentation Effect of Kadsuralignan F on Melan-A Murine Melanocytes and Human Skin Equivalents

The development of melanogenic inhibitors is important for the prevention of hyperpigmentation, and, recently, consideration has been given to natural materials or traditionally used ingredients such as Chinese medicine. The aim of this study is the evaluation of a new anti-melanogenic candidate, kadsuralignan F, from the natural plant Kadsura coccinea, as well as the determination of mechanisms of melanogenesis inhibition at a molecular level. Kadsuralignan F significantly reduced melanin synthesis in a dose-dependent manner in a murine melanocyte cell line and human skin equivalents. There was no direct inhibition on mushroom tyrosinase or cell-extract tyrosinase activity, and mRNA expression of tyrosinase and other melanogenic genes such as tyrosinase-related protein-1 (trp-1) or trp-2 were not affected by kadsuralignan F. Interestingly, the protein level of tyrosinase was dramatically downregulated with kadsuralignan F treatment. We found that a decrease of tyrosinase protein by kadsuralignan F was fully recovered by MG132, a proteasome inhibitor, but not by chloroquine, a lysosome inhibitor. In this study, we found that kadsuralignan F, a lignan from an extract of Kadsura coccinea, has an inhibitory activity on melanin synthesis through tyrosinase degradation. These findings suggest that kadsuralignan F can be used as an active ingredient for hyperpigmentation treatment.     

Marliolide Derivative Induces Melanosome Degradation via Nrf2/p62-Mediated Autophagy

Nuclear factor erythroid 2-related factor 2 (Nrf2), which is linked to autophagy regulation and melanogenesis regulation, is activated by marliolide. In this study, we investigated the effect of a marliolide derivative on melanosome degradation through the autophagy pathway. The effect of the marliolide derivative on melanosome degradation was investigated in α-melanocyte stimulating hormone (α-MSH)-treated melanocytes, melanosome-incorporated keratinocyte, and ultraviolet (UV)B-exposed HRM-2 mice (melanin-possessing hairless mice). The marliolide derivative, 5-methyl-3-tetradecylidene-dihydro-furan-2-one (DMF02), decreased melanin pigmentation by melanosome degradation in α-MSH-treated melanocytes and melanosome-incorporated keratinocytes, evidenced by premelanosome protein (PMEL) expression, but did not affect melanogenesis-associated proteins. The UVB-induced hyperpigmentation in HRM-2 mice was also reduced by a topical application of DMF02. DMF02 activated Nrf2 and induced autophagy in vivo, evidenced by decreased PMEL in microtubule-associated proteins 1A/1B light chain 3B (LC3)-II-expressed areas. DMF02 also induced melanosome degradation via autophagy in vitro, and DMF02-induced melanosome degradation was recovered by chloroquine (CQ), which is a lysosomal inhibitor. In addition, Nrf2 silencing by siRNA attenuated the DMF02-induced melanosome degradation via the suppression of p62. DMF02 induced melanosome degradation in melanocytes and keratinocytes by regulating autophagy via Nrf2-p62 activation. Therefore, Nrf2 activator could be a promising therapeutic agent for reducing hyperpigmentation.     

Multiple uses of Essential Oil and By-Products from Various Parts of the Yakushima Native Cedar (Cryptomeria Japonica)

This article presents multiple potential uses of the Yakushima native cedar (Cryptomeria japonica), known in Japan as the Yaku-sugi tree. The Yaku-sugi was divided into four parts: leaves, branches with leaves, branches, and stems. We obtained the essential oil, hydrosol, distillation residue, and distillation wastewater from the trees. Essential oil and hydrosol were determined to be volatile organic compounds. All samples were screened for the following bioactivities: antioxidative, antibacterial, and anti-melanogenesis activities. Freeze-dried distillation residue was tested to assess whether it had a deodorizing effect. The main component of the leaf essential oil was found to be monoterpenes. In contrast, the stem essential oil mainly contained sesquiterpenes. In terms of bioactivities, the leaf essential oil showed antibacterial activity and the stem essential oil showed anti-melanogenesis activity. Distillation residue and wastewater showed many activities, including antioxidant, antibacterial, and anti-melanogenesis activities. Moreover, the residue had a deodorizing effect against ammonia.