Curcumin-Based Tyrosinase-Targeting Derivatives for Cell Imaging and Depigmenting Effect

Targeting melanogenesis through tyrosinase inhibition represents a key therapeutic strategy, highlighting the need for novel molecules capable of modulating melanin synthesis and/or serving as fluorescent probes for cellular and melanoma tracking. In this study, two curcumin (CUR) derivatives, CUR-C3-PP 1 and CUR-CO-PP 2, were designed and successfully synthesized by strategic integration of a 4-(piperazin-1-yl)phenol pharmacophore into CUR skeleton. In vitro enzymatic assays against Agaricus bisporus tyrosinase (AbTYR) revealed that derivatives CUR-C3-PP 1 and CUR-CO-PP 2 amplified the diphenolase inhibitory capacity (IC₅₀ values of 51.20 μM and 12.89 μM, respectively) when compared to parent curcumin (IC₅₀ = 168.57 μM). Notably, CUR-CO-PP 2 emerged as the most potent candidate, significantly eclipsing native CUR and outperforming the standard inhibitor kojic acid (KA). Enzyme kinetics and molecular docking simulations rationalized this enhanced profile, and the mechanism of inhibitory effects for compounds CUR-C3-PP 1 and CUR-CO-PP 2. Cellular assays highlighted that CUR-C3-PP 1 retained functional intrinsic luminescence, displaying selective accumulation and intense fluorescence within the cytoplasm of B16-F10 melanoma cells alongside preferential cytotoxicity. Screening in zebrafish (Danio rerio) embryos confirmed that both derivatives maintain an excellent biocompatibility profile up to 20 μM. In vivo, both compounds elicited robust, dose-dependent depigmentation, with CUR-CO-PP 2 closely approaching the efficacy of the control 1-phenyl-2-thiourea (PTU). Collectively, our findings demonstrate that the imaging and anti-melanogenic properties of curcuminoids can be independently optimized through rational linker modification, establishing CUR-C3-PP 1 as a promising fluorescent tracer for imaging and CUR-CO-PP 2 as a candidate for depigmenting therapies.