Unambiguous identification of γ-aminobutyric acid adducts as novel plant biomarkers and their ultra-sensitive detection by UPLC–MS/MS for retrospective analyses of nitrogen mustards exposure

Abstract

Plants are widely existing in the environments and have been considered as potential sentinel species of toxic chemicals′ exposure. In this study, the deadly toxic chemicals of three nitrogen mustards (NMs, including NH1, NH2 and NH3) were selected as the investigated targets. First, the reactivities of common endogenous plant components with NMs were examined in vitro. Then, the model plant Nicotiana benthamiana Domin was exposed to NMs. Three γ-aminobutyric acid–nitrogen mustard adducts (GABA–NMs) were identified in the living plant by high resolution mass spectrometry and comparison with the synthesized references. A sensitive detection method with the limits of quantification of 0.0500ngmL-1 was developed using ultrahigh performance liquid chromatography–triple quadrupole mass spectrometry. The GABA–NMs could be detected after 120 days of the exposure and even in the dead leaves without obvious decrease. Furthermore, 20 different plant species grown in diverse climate zones were exposed to HN1, and the adduct of GABA–HN1 was identified in all the leaves. The results showed the good universality and specificity of GABA–NMs as plant biomarkers for NMs exposure. This work provides a new approach for the pollution investigation of toxic chemicals through analysing biomarkers in plant materials. Environmental implicationNitrogen mustards (NMs) are lethal blistering agents, which are listed as Schedule 1 toxic chemicals by the Organisation for the Prohibition of Chemical Weapons (OPCW). OPCW has established the worldwide network of laboratories for environmental analysis for the abuse surveillance of the lethal chemicals. NMs entering the environment will cause great harms to organisms, including cytotoxicity and genotoxicity. In this work, γ-aminobutyric acid adducts in plants after exposure to NMs were identified as biomarkers to trace the attack or leakage in the environment. The work provides a novel promising approach to evaluate environmental hazards from toxic chemicals.