LC-MS/MS determination of the isomeric neurotoxins BMAA (β-N-methylamino-L-alanine) and DAB (2,4-diaminobutyric acid) in cyanobacteria and seeds of Cycas revoluta and Lathyrus latifolius

Since diverse taxa of cyanobacteria has been linked to biosynthesis of BMAA, a controversy has arisen about the detection of neurotoxic amino acids in cyanobacteria. In this context, a novel LC-MS/MS method was developed for the unambiguous determination of beta-N-methylamino-L-alanine (BMAA) and 2,4-diaminobutyric acid (DAB) in cyanobacteria and selected plant seeds. Both neurotoxic and non-proteinogenic amino acids were analyzed without derivatization considering the total concentration of the free and protein-bound form. The investigation of overall 62 cyanobacterial samples of worldwide origin by application of this method revealed the absence of BMAA, whereas seeds of Cycas revoluta contained 6.96 mu g g(-1) of free BMAA. In contrast, the isomer DAB was confirmed in 16 cyanobacterial samples in concentrations of 0.07-0.83 mu g g(-1),whereof one sample is distributed as nutritional supplement. In addition, seeds of Lathyrus latifolius contained 4.21 mu g g(-1) of free DAB. Limits of detection were for BMAA < 1.0 mu g g(-1) in the cyanobacterial matrix and < 0.14 mu g g(-1) in angiosperm seeds. DAB exhibits higher sensitivities of <0.06 mu g g(-1) in cyanobacteria and <0.008 mu g g(-1) in angiosperm seeds. The highly specific analysis method with increased detection sensitivity eliminates the disadvantages of derivatization-based methods to be discussed. (C) 2009 Elsevier Ltd. All rights reserved.