A 96-Well Plates-based UV Spectrophotometric Assay for Determination of Total Glucosinolates in Isatis indigotica Roots

Background: Glucosinolates (GLS) are important secondary metabolites in Cruciferae vegetables and herbs. Currently, the assays of total GLS determination are cumbersome (requiring acidic or enzymatic hydrolysis and addition of staining reagents), time-consuming, and indirect. High concentrations of inorganic salts are inevitably incorporated into the GLS products during separation. There is a need for a quantitative method for simple and rapid determination of total GLS after desalting process. Methods: A 96-well plates-based UV spectrophotometric method for determination of total GLS of Isatis indigotica roots was developed in the present study. The detection wavelength is set at 230 nm using quartz plates. This assay was validated using gluconapin and sinigrin as reference standards, and applied to determine the total GLS of I. indigotica roots prepared from five different desalting methods. Results: This assay is specific for total GLS prepared from I. indigotica roots, and it has acceptable accuracy (91.76–98.18% for quality control, and 95.59–102.52% for addition/recovery), precision (0.24–0.70% pooled RSD), reproducibility (0.31–1.84% RSD), and stability (0.24–1.45% RSD) over a 72-h period. Conclusion: The 96-well plates-based UV spectrophotometric assay is simple and accurate for high-throughput determination of total GLS.