An Examination of the Free Amino Acids of the Common Onion (Allium cepa) a

SUMMARY Free amino acids in four onion cultivars were studied by two‐dimensional ascending paper chromatography with the following solvents: 1) phenol‐water, 8:2 (v/v), 2) n‐butanol‐acetic acid‐water, 4:1:5 (v/v) (upper layer); and 1) sec butanol–tert butanol‐methylethyl ketone–water, 4:4:8:5 (v/v), 2) n ‐butanol–acetic acid‐water, 4:1:5 (v/v) (upper layer). The amino compounds identified in the extracts were: glutathione, aspartic acid, cysteine, cystine, glutamic acid, serine, canavanine, asparagine, glycine, arginine, lysine, threonine, tyrosine, methionine sulfoxide, alanine, dihydro‐alliine, S‐methyl cysteine, tryptophan, methionine, valine, phenylalanine, and mixed leuycines. Suspected as present was α‐L‐glutamyl‐S‐[β‐carboxy‐n‐propyI]‐L‐cysteinyl glycine. Densitometry and colorimetry were used to determine the relative approximate amounts of alanine, aspartic acid, arginine, glutamic acid, glycine, leucines, lysine, methionine sulfoxide, phenylalanine, serine, S‐methyl cysteine, threonine, tyrosine, and valine. The more abundant amino acids were: arginine, glutamic acid, phenylalanine, leucines, tyrosine, lysine, and methionine sulfoxide.