Analysis, occurrence, and toxicity of ß-methylaminoalanine (BMAA)

A risk for the consumer?

image of Analysis, occurrence, and toxicity of ß-methylaminoalanine (BMAA)

In 2005 an international research team reported that cyanobacteria living in symbiosis with plants or living free in lakes and oceans are able to produce the non-protein amino acid -methylaminoalanine, also known as BMAA. Some years earlier the American scientists in this team had reported that BMAA could be found not only in the brain from diseased patients of the Chamorro people on Guam having the neurodegenerative diseases amyotrophic lateral sclerosis (ALS) and Parkinsons dementia (PD), but also in two patients with Alzheimers disease in Canada. A very high incidence of ALS and PD among the Chamorro people had been known since after the Second World War and had been linked to the use of flour prepared from the seeds of the local cycad tree, which had been shown to contain BMAA. As surface water is frequently purified and used as drinking water, it was hypothesised that low level of contamination of drinking water with BMAA from the cyanobacteria might reach the human brain and over time result in neurodegenerative disease. This reports aimed at scrutinizing this hypothesis, and concludes that BMAA is unlikely to occur in drinking water and be responsible for these neurological diseases in the Western World.



The theory of biomagnification and identification of BMAA in human tissues

Because of the difficulty to explain a “slow toxin”-action of watersoluble free BMAA molecules on the neurological system, Murch et al. (2004a) investigated the possibility of biomagnification of BMAA and leakage from bound forms of BMAA. They found that axenic cultures of cyanobacteria, initially isolated from collaroid cycad roots, contained approximately 240 times more bound BMAA than free BMAA, 72 as compared to 0.3 mg/kg bacteria. Collaroid roots of the cycad Cycas micronesica contained 2 mg BMAA per kg root in bound form. As noncollaroid roots had no symbiosis with cyanobacteria and contain no BMAA, it seems as though BMAA has to leak out from the cyanobacteria and be taken up by the collaroid cycad roots. When other cycad tissues were investigated the results pointed to that leaf tissue contained 738 mg BMAA per kg tissue, outer seed layers 48 mg BMAA per kg tissue, the sarcotesta 89 mg per kg tissue, and the female gametophyte 81 mg BMAA per kg tissue. These observations do not only suggest that the total BMAA exposure may be higher than that indicated by the amount of free BMAA, but also that the amount of BMAA found may increase going from cyanobacteria to cycads.


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