Diastereoisomeric 4-substituted acidic amino acids in ferns

Abstract

Diastereoisomeric 4-substituted acidic amino acids occur in characteristic associations in the green parts of some species of the Filicinae. Subspecies of Phyllitis scolopendrium accumulate 2( S),4( R)-4-methylglutamic acid, 2( S)-4-methyleneglutamic acid and the two diastereoisomers of 2( S)-4-hydroxy-4-methylglutamic acid, the last two occurring at relative concentrations of 3: 1. All Asplenium species investigated were distinctive in accumulating 2( S),4( R)-4-methylglutamic acid, the two diastereoisomers of 2( S)-4-hydroxy-4-methylglutamic acid, and the two diastereoisomers of 2( S)-4-hydroxy-2-aminopimelic acid in a characteristic concentration ratio. Some Polystichum species do not accumulate 4-substituted acidic amino acids whereas others accumulate both diastereoisomers of 2( S)-4-hydroxy-4-methylglutamic acid and 'of 2( S)-4-hydroxy-2-aminopimelic acid, and thus resemble Asplenium species. The seasonal variation in the concentration of 4-substituted acidic amino acids in the green parts of Phyllitis, Asplenium and Polystichum species has also been determined.