Meta-carboxy-substituted aromatic amino acids and γ-glutamyl peptides: Chemical characters for classification in the Iridaceae

Abstract

Free amino acids and γ-glutamyl peptides have been examined in 116 species of Iridaceae. 3-(3-Carboxyphenyl)-alanine, 3′-carboxyphenylglycine and γ-glutamyl peptides occur widely in the subfamily Iridoideae but have not been found in the two other subfamilies, Ixioideae and Sisyrinchoideae. The two aromatic amino acids occur in varying concentrations in species within the Irideae and Tigrideae. The γ-glutamyl peptides are distributed in a distinct pattern within the Irideae. The results are discussed in relation with botanical classification of the subfamily Irioideae and with existing knowledge on the occurrence, biosynthesis and degradation of the aromatic amino acids and the γ-glutamyl peptides.