Synthesis of monopyrenylalkylamine derivative 1 and its fluorescence behavior for Cu2+ in H2O/CH3CN (1:1, v/v) were investigated. Upon Cu2+ binding, 1, bearing a sulfonamide group, exhibited a marked excimer emission at 455 nm along with a weak monomer emission at 375 nm. The excimer emission, driven by formation of an intermolecular pyrenyl static excimer upon Cu2+ binding to the sulfonamide group, is rationalized by experimental and theoretical DFT calculation results.

Several studies observed that adiponectin, an important adipokine that improves glucose metabolism by regulating AMP-activated protein kinase (AMPK) signaling, is dermatologically beneficial. In our recent microarray data, we found that adiponectin expression was lower in lesional skin than in non-lesional skin of melasma patients. Given that AMPK is a key adiponectin signaling mediator, we investigated the role of adiponectin and AICAR, a cell-permeable AMPK activator, in melanogenesis. We herein showed that adiponectin and AICAR downregulated MITF, tyrosinase, TRP-1, and DCT expression and reduced melanin content in normal human and mouse melanocytes. The depigmenting effect of adiponectin was mediated via AMPK activation, which induced the inhibitory phosphorylation of CREB-regulated transcription co-activators (CRTCs) and subsequent suppression of the novel CRTC/CREB pathway in melanocytes. These findings suggest that adiponectin and its analogs are useful as a clinical strategy for treating hyperpigmentation disorders.