Solid phase extraction of β-N-methylamino-L-alanine (BMAA) from South African water supplies

Abstract

β-N-methylamino-L-alanine (BMAA) has been implicated in amyotrophic lateral sclerosis/parkinsonism dementia complex (ALS/PDC) and is assumed to cause or contribute to this neurodegenerative disease after bioaccumulation and slow release of BMAA from a protein-associated form and conversion to the excitatory carbamate form. BMAA has been detected in varying quantities in freshwater cyanobacteria, causing some concern regarding the potential for direct dietary consumption of BMAA-containing water and subsequent intoxication. Considering the BMAA content reported in cyanobacteria and the concentrations cyanobacterial cells can reach in a bloom in freshwater impoundments, BMAA concentrations could potentially reach the mg∙ℓ^-1 range. BMAA has been shown to cause neuronal injury and even death at μM exposure ranges. Current analytical techniques are, however, insufficiently sensitive to detect the molecule at concentrations of less than 250 ng∙ℓ^-1 without prior concentration. Safe levels have yet to be determined for BMAA in potable water but these levels may be far below this analytical limit. It is therefore necessary to quantify potential exposure at these relatively low levels. A simple method is described here for high levels of BMAA recovery from a range of waters (78-103 ± 5%), as well as an amino acid matrix (57 ± 5%), saline solution (63 ± 5%), tap water (61 ± 5%) and a preliminary analysis of BMAA concentrations from bloom and non-bloom freshwater supply samples. No exogenous BMAA was detected in water supplies, despite high concentrations in the bloom material, suggesting that BMAA is not released or exported by the cyanobacteria or that rapid degradation, binding or uptake of BMAA occurs in these environments. This method is not suggested for marine samples a
very low recovery percentages are seen in the presence of sodium.

Keywords: β-N-methylamino-L-alanine, BMAA, cyanobacterial bloom, solid phase extraction