Screening for Non-Protein Amino Acids in Seeds of the Guam Cycad, Cycas circinalis, by an Improved GC-MS Method

Abstract

The non-protein amino acid, β-N-methyl-amino-L-alanine (L-BMAA) from Cycas circinalis seeds, has been implicated as a causative agent of amyotrophic lateral sclerosis - Parkinsonism dementia complex (ALS-PDC), a disease known from Guam and other areas in the western Pacific. We analyzed C. circinalis seeds for additional free non-protein amino acids by a recently developed GC-MS method. The samples were prepared by water extraction of seed flour. The amino acids present in the extract were derivatized by N(O,S)-isobutyloxycarbonylation of the amine functional groups and then tert-butyldimethylsilylation of the carboxyl functional groups. Peaks for a total of seventeen derivatives of non-protein amino acids were detected by GC-MS. In addition to L-BMAA, four other non-protein amino acids were identified as β-alanine, γ-aminobutyric acid, pyroglutamic acid, and α-aminoadipic acid.

Key words

Non-protein amino acids - Cycas circinalis L. - Cycadaceae - amyotrophic lateral sclerosis-Perkinsonism dementia complex - N(O,S)-isobutyloxycarbonylation - tert-butyldimethylsilylation - gas chromatography-mass spectrometry