Determination of 2-Thioxo-3-pyrrolidinecarbaldehyde in Salted Radish Root (Takuan-zuke) by High-Performance Liquid Chromatography with Fluorescence Detection after Pre-Column Derivatization Using 4-(N,N-dimethylaminosulfonyl)-7-hydrazino-2,1,3-benzoxadiazole

Abstract

2-thioxo-3-pyrrolidinecarbaldehyde (TPC) is an important intermediate in the yellowing of Japanese pickles “takuan-zuke”. TPC has been reported to have antibacterial activity against bacteria causing food poisoning and microorganisms associated with the development of caries, as well as various physiological functions such as antimutagenicity. However, since TPC has high reactivity, robust quantitative analysis is difficult with the extraction method or pre-column derivatization method using 2,4-dinitrophenylhydrazine. In this study, a high-performance liquid chromatography (HPLC) method involving labeling with 4-(N,N-dimethylaminosulfonyl)-7-hydrazino-2,1,3-benzoxadiazole (DBD-H) was developed for the determination of the level of TPC in takuan-zuke. DBD-TPC was successfully stabilized by adding a buffer solution to the reaction solution, which established continuous analysis by HPLC using an autosampler. The DBD-TPC calibration curve was linear in the range of 0.25–250 nmol/mL (final concentration) and showed a wide dynamic range. The lower limit of detection was 0.205 nmol/mL in TPC standard. The proposed method was successfully applied to the measurement of TPC in daikon-oroshi. The results reveal the possibility of determining the variation of TPC level in processed foods containing radish. We concluded that the proposed method is useful for evaluating the quality of processed radish products.

Keywords

• 2-thioxo-3-pyrrolidinecarbaldehyde
• 4-(N,N-dimethylaminosulfonyl)-7-hydrazino-2,1,3-benzoxadiazole
• daikon-oroshi
• takuan-zuke
• aldehyde analysis