The structure elucidation and synthesis of the luciferin from the recently discovered luminous earthworm Fridericia heliota is reported. This luciferin is a key component of a novel ATP-dependent bioluminescence system. UV, fluorescence, NMR, and HRMS spectroscopy studies were performed on 0.005 mg of the isolated substance and revealed four isomeric structures that conform to spectral data. These isomers were chemically synthesized and one of them was found to produce light when reacted with a protein extract from F. heliota. The novel luciferin was found to have an unusual extensively modified peptidic nature.
We also report isolation and structure elucidation of Fridericia oxyluciferin, which provides insight into a novel bioluminescence mechanism in nature. Oxidative decarboxylation of a lysine fragment of luciferin supplies energy for light generation, while a fluorescent CompX moiety remains intact and serves as a light emitter.