An Improved Spectrophotometric Method for Quantificationally Measuring Total Glucosinolates Content in Tumorous Stem Mustard (Brassica juncea var. tumida)

Glucosinolates is a class of secondary metabolites with anti-inflammatory and anti-obesity properties and an intense bitter taste in tumorous stem mustard (TSM), which are used to produce a famous pickle named Zhacai. Spectrophotometric, chromatographic, or infrared techniques showed capacity to evaluate glucosinolate level. The aim of current study was to improve a spectrophotometric methodology to quantify total glucosinolates content (TGC) in TSM. Microwave treatment at medium temperature for 20 s was used to improve the previous method of water bath in enzyme inactivation. Absorbance should be tested at 420 nm for measuring TGC, while not 450 nm. The optimized extraction conditions of glucosinolates were that solid-liquid ratio was 1:22; temperature was 60°C; time was 30 min. The regression curve used for TGC calculation was made using a variety of individual glucosinolate. Recovery rate and variable coefficient of TGC quantitation in TSM were 103% and 5.98%. These results obtained by this method have high consistency within 3 days. In addition, we also introduced the limitations of this method.