Distinguishing the cyanobacterial neurotoxin beta-N-methylamino-L-alanine (BMAA) from its structural isomer 2,4-diaminobutyric acid (2,4-DAB).

The cyanobacterial neurotoxin beta-N-methylamino-L-alanine (BMAA) has been associated with certain forms of progressive neurodegenerative disease, including sporadic Amyotrophic Lateral Sclerosis and Alzheimer's disease. Reports of BMAA in cyanobacterial blooms from lakes, reservoirs, and other water resources continue to be made by investigators in a variety of laboratories. Recently it was suggested that during analysis BMAA may be confused with its structural isomer 2,4-diaminobutyric acid (2,4-DAB), or that current detection methods may mistake other compounds for BMAA. We here review the evidence that BMAA can be consistently and reliably separated from 2,4-DAB during reversed-phase HPLC, and that BMAA can be confidently distinguished from 2,4-DAB during triple quadrupole LC-MS/MS analysis by i) different retention times, ii) diagnostic product ions resulting from collision-induced dissociation, and iii) consistent ratios between selected reaction monitoring (SRM) transitions. Furthermore, underivatized BMAA can be separated from 2,4-DAB with an amino acid analyzer with post-column visualization using ninhydrin. Other compounds that may be theoretically confused with BMAA during chloroformate derivatization during GC analysis are distinguished due to their different retention times.

Effects of the cyanobacterial neurotoxin beta-N-methylamino-L-alanine on the early-life stage development of zebrafish (Danio rerio).

beta-N-Methylamino-L-alanine (BMAA), a neurotoxic amino acid, is produced by members of all known groups of cyanobacteria. In the presence of added carbonate, BMAA generates an analogue of glutamate which has been associated with motor neuron (MN) diseases via a mechanism of motor neurone specific excitotoxicity. The toxicity of BMAA has been established in various mammalian test models, but the widespread aquatic production of BMAA raises questions of BMAA toxicity to aquatic organisms. Zebrafish (Danio rerio) embryos were exposed to varying concentrations of BMAA (5-50,000 microgl(-1)) with and without added carbonate. BMAA exposure induced a range of neuro-muscular and developmental abnormalities in D. rerio, which can be directly related to disruptions to glutamatergic signalling pathways. When exposed to BMAA plus added carbonate, the incidence of pericardial oedema increased by up to 21% in test subjects, correlating with a reduction in heart rate. Increased incidence of abnormal spinal axis formation was seen in all D. rerio larvae exposed to BMAA concentrations of >or=50microgl(-1), with a further 10% increase from >or=500 microgl(-1) BMAA when carbonate species were present. A dose-dependent increase in clonus-like convulsions was observable in embryos exposed to >or=5 microgl(-1) BMAA+/-added carbonate. This is the first study on the neuro-muscular and developmental effects of BMAA exposure on aquatic vertebrates. The present findings, plus the potentially widespread production of BMAA in aquatic cyanobacteria, indicate a need for information of exposure levels, duration and toxic outcomes in aquatic biota.