Colorimetric detection of indole-3-carbaldehyde in white cauliflower by self-condensation reaction giving urorosein

: This work presents a spectrophotometric method for the determination of indole-3-carbaldehyde (I3A), a bioactive metabolite of tryptophan, in white cauliflower (Brassica oleracea L. var. botrytis). The colorimetric assay is based on the self-condensation of I3A under acidic conditions, forming di-indolylmethine salt (urorosein). The absorbance of urorosein at 490 nm was used for I3A quantification with a microplate reader. Key parameters, including acidity, solvent composition, temperature, and reaction time, were optimized to achieve the best analytical performance. This method exhibited a linear dynamic range up to 100 μM with excellent repeatability (avRSD 1.7 %) and a high coefficient of determination (R2 0.9975). The limit of detection and quantification were 0.469 ± 0.007 μM and 1.562 ± 0.023 μM, respectively. As proof of concept, the assay was applied to white cauliflower extract, achieving a 113 % recovery compared to LC-MS analysis. This method potentially offers a simple approach for the detection of I3A in foods.