Gas chromatographic determination of azetidine-2-carboxylic acid in rhizomes of Polygonatum sibiricum and Polygonatum odoratum

The rhizomes of Polygonatum are used as supplements in many foods including tea. Azetidine-2-carboxylic acid (ACA) in P. rhizomes is a potent toxin that could be incorporated into proteins in place of proline leading to protein dysfunction. Quantification of ACA in Polygonatum species can contribute to establish safety in food industry. Our study provides ACA levels in Polygonatum sibiricum and Polygonatum odoratum, which are widely used in Korea. Hot water extract of samples was silylated with N,O-Bis(trimethylsilyl)trifluoroacetamide in the presence of 1-octanol as an internal standard, analyzed by GC with flame ionization detector (FID) and mass spectrometry (MS). The developed assay showed excellent linearity and sensitivity. The limit of detection (LOD) and quantification (LOQ) were 2.9 and 7.8 μg/mL, respectively. The relative standard deviations (RSDs) of intra-day and inter-day precision were <1.8% and <4.8%, respectively. The content of ACA in P. sibiricum (5.39 ± 1.67 mg/g, N = 29, mean ± standard deviation) was significantly lower than that in P. odoratum (9.23 ± 3.67 mg/g, N = 20). Our study demonstrates a rapid and sensitive quantitative assay for determination of ACA in Polygonatum species with simple derivatization and gas chromatographic analysis, which could be utilized in general food industries.