Camalexin quantification using HPLC and the novel internal standard thiabendazole

Camalexin is the key phytoalexin in Arabidopsis thaliana and crops such as Camelina sativa. It is typically quantified by liquid chromatographic methods using camalexin dilutions as external standards. Alternatively, 6-fluoroindole-3-carboxaldehyde (6-FICA) is used as an internal standard with the advantage that identical conditions can be used for the analyte and standard, but two detectors are needed (ideally fluorescence for camalexin; UV for 6-FICA). We established an easy method to use readily available, cheap thiabendazole as a novel internal standard, facilitating the use of a fluorescence detector for standard and analyte for fast, reliable camalexin quantification in samples of diverse biological origin.