Reducing the Formation of Toxic Byproducts During the Photochemical Release of Epinephrine

Engineered light-sensitive molecules offer a sophisticated toolkit for the manipulation of biological systems with both spatial and temporal precision. Notably, artificial "caged" compounds can activate specific receptors solely in response to light exposure. However, the uncaging process can lead to the formation of potentially harmful byproducts. For example, the photochemical release of adrenaline (epinephrine) is accompanied by the formation of adrenochrome, which has neuro- and cardiotoxic effects. To investigate this effect in detail, we synthesized and compared two "caged" epinephrine analogs. The first was a classical compound featuring an ortho-nitrobenzyl protecting group attached to the amino group of epinephrine. The second analog retained the ortho-nitrobenzyl group but included an additional carbamate linker. The photolysis of both compounds was conducted under identical conditions, and the resulting products were analyzed using UV-Vis spectroscopy, chromatography, and NMR techniques. Surprisingly, while the classical compound led to the formation of adrenochrome, the carbamate-type caged epinephrine did not produce this byproduct, resulting in the clean release of the active substance. Subsequently, we assessed the novel compound in an in vitro platelet activation assay. The results demonstrated that the uncaging of epinephrine significantly enhances platelet activation, making it a valuable tool for advanced signaling studies.