ABSTRACT: Plant research and natural product detection are of sustainable interests. Benefited by direct detection with no sample preparation, sinapine, a bioactive chemical usually found in various seeds of Brassica plants, has been unambiguously detected in radish taproot (Raphanus sativus) tissue using a liquid-assisted surface desorption atmospheric pressure chemical ionization mass spectrometry (DAPCI-MS). A methanol aqueous solution (1:1) was nebulized by a nitrogen sheath gas toward the corona discharge, resulting in charged ambient small droplets, which affected the radish tissue for desorption/ionization of analytes on the tissue surface. Thus, sinapine was directly detected and identified by tandemDAPCI-MS experiments without sample pretreatment. The typical relative standard deviation (RSD) of this method for sinapine detection was 5-8% for six measurements (S/N = 3). The dynamic response range was 10-12-10-7 g/cm2 for sinapine on the radish skin surface. The discovery of sinapine in radish taproot was validated by using HPLC-UV methods. The data demonstrated that DAPCI assisted by solvent enhanced the overall efficiency of the desorption/ionization process, enabling sensitive detection of bioactive compounds in plant tissue.

KEYWORDS: DAPCI, sinapine, radish taproot, plant tissue, tandem mass spectrometry, LTQ-MS

2011-Dejuan Huang, Liping Luo- J. Agric. Food Chem.pdf