Abstract
Acidic non-protein amino acids and peptides in five species belonging to the family Liliaceae -Smilax china, Lilium maximowiczii, Tulipa gesneriana, Allium cepa and A. sativum- were surveyed. Two new amino acids -4-hydroxymethyl- and 4-ethyl-4-hydroxyglutamic acid- were isolated from bulbs of T. gesneriana. The first unequivocal identification of 4-ethylglutamic acid was performed from the same plant tissue. A new dipeptide -S-(2-carboxy-n-propyl)cysteinyl glycine- was isolated from A. cepa. Besides the compounds described above, 4-methylene-, 4- methyl- and 4-hydroxy-4-methylglutamic acid were isolated from S. china, L. maximowiczii, and T. gesneriana, but 4-ethylideneglutamic acid was isolated only from T. gesneriana. 4- Methyleneglutamic acid showed no appreciable biological activity, although this amino acid has an α, β-unsaturated carboxyl group and reacts easily with cysteine in vitro. The most abundant free amino acid in the plant tissues examined in this study is arginine ; nevertheless, acidic Nα- acylarginine derivatives which have been found in S. china and L. maximowiczii and published elsewhere could not be detected in bulbs of T. gesneriana, A. cepa, and A. sativum.
