Development of a fluorimetric detection method for cinnabarinic acid using ortho-tolyl hydrazine as the derivatization reagent.

A fluorimetric detection method for one of the tryptophan metabolites, cinnabarinic acid (CA), which has recently been reported to have the ability to induce apoptosis in thymocytes, was developed using o-tolyl hydrazine (TH) as the derivatization reagent. The carbonyl group at position 3 in CA was tagged with the hydrazino moiety of TH at 100 degrees C for 30 min, and the generated derivative, CA tagged with TH, fluoresced at 412 nm with a 316 nm excitation wavelength. The CA tagged with TH was separated on a reversed-phase HPLC and detected fluorometrically. The relative standard deviation was in the range of 1.1-8.9% (n = 3), and the detection limit was approximately 12?fmol (signal-to-noise ratio, 3). The proposed HPLC method can be useful for the sensitive detection of CA.