Analysis of 3‐nitropropionic acid in Fabaceae plants by HPLC‐MS/MS

Introduction 3-Nitropropionic acid (3-NPA) is a toxic compound that can accumulate in esterified form in the Fabaceae family. In the Lotae tribe, many species have been identified as 3-NPA producers (e.g., Securigera varia), while some of the genetically close Lotae plants were formerly reported as 3-NPA-free (e.g., Lotus corniculatus and Anthyllis vulneraria). These plants are used as forage and have a tradition in ethnomedicine, also, the extracts of A. vulneraria are used in cosmetics. Objectives Our aim was to investigate the 3-NPA content of these selected Fabaceae species and to develop a validated quantitative method to evaluate 3-NPA concentrations in extracts of different herbal parts and cosmetic products. Materials and Methods A UHPLC-ESI-Orbitrap-MS/MS method was applied for detection and identification of 3-NPA derivatives in the form of glucose esters. For the quantitative analysis, an optimized sample processing method was developed. The free 3-NPA content was determined using HPLC-ESI-MS/MS. Results 3-NPA esters could be detected in all three species, but their quantity showed a high variation. S. varia contained 0.5-1.0 g/100 g of 3-NPA, while in L. corniculatus samples only trace quantities were detectable, below the LOQ (25 ng/ml). Most of the A. vulneraria samples showed similarly low concentrations, but one sample had 3-NPA levels comparable to S. varia. 3-NPA could not be detected in the tested cosmetics containing A. vulneraria extracts. Conclusions Using highly sensitive analytical methods, new 3-NPA-containing species were identified. The developed validated quantitative method is suitable for the determination of 3-NPA concentrations in herbal samples.