Analysis of 2-Amino-3-Methylaminopropanoic Acid and Its Link to Guamanian Amyotrophic Lateral Sclerosis
Crowley, Jeffrey S.
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Amyotrophic lateral sclerosis (ALS) occurs in a high incidence on tht; south Pacific islands of Guam and Rota. Research aimed at elucidating the etiology of this disease has implicated the Cycas circinalis L. (cycad plant), a plant consumed by the indigenous population. In particular, the putative neurotoxin 2-amino-3-methylaminopropanoic acid (BMAA), present in the cycad plant, has recently been shown to induce a primate motofsystem disorder which is functionally similar to the ALS syndrome as it is found on Guam. This finding has demonstrated the need for precise quantitative information regarding the levels of BMAA present in the cycad plant, and in the cycad food products prepared by the native Guamanians. Gas chromatography/mass spectrometry has been explored as a means of providing this information, and it was found that the total hydrolyzable and unhydrolyzable BMAA present in the female gametophyte tissue (the part of the cycad seed that is most commonly consumed) is 0.092% of the fresh seed weight. Further, it was found that the water soaking procedure employed by the Guamanians is effective at removing all detectable traces of BMAA from the gametophyte tissue. In view of the large doses and long time periods required to induce neurological symptoms in primates, these data suggest that the trace amounts of BMAA remaining in washed cycad seeds are an unlikely cause of Guamanian amyotrophic lateral sclerosis.