Quinone-derived π-extended phenazines as new bioimaging probes for the staining of lipid droplets in live cells

Fluorescent compounds have been used as contrast agents for staining subcellular organelles in order to provide visualization of intracellular biomolecules. Among these structures lipid droplets (LD) highlights, not only as a lipids compartment but also playing important role in homeostasis celular.
As a part of our ongoing interest in development of fluorescents agents for staining subcellular structures, herein, we describe a synthetic strategy for the preparation of new fluorescent π-extended phenazines from lapachol, a naturally occurring naphthoquinone isolated from the Tabebuia species (ipe tree). Lapachol, through Hooker oxidation, afforded nor-lapachol, which was cyclized to nor-β-lapachone, in acid conditions. Reaction of nor-β-lapachone with 1,2-Diaminobenzene or 3,6-dibromobenzene-1,2-diamine provided the respective phenazines. Cross-coupling reactions were performed in order to acess more con-jugated fluorescents compounds was also accomplished
Cell-imaging experiments identified P1 as an imaging agent marker for intracellular LD in live cells in co-localization assays with the lipophilic tracker Nile Red.