Comparative Chromatographic Analysis of Amino Acids in the Seeds of Three Nigella L. Representatives

Amino acids are an important class of primary metabolites that can exhibit various pharmacological activities. In this study, the comparative gas chromatography–mass spectrometry (GC/MS) analysis of free and total amino acids in the seeds of three representatives of the Nigella L. genus (Nigella arvensis L., Nigella damascena L. [cultivar “Rizdvyana zirochka”], and Nigella sativa L. [cultivar “Faraon”]) was conducted under their cultivation in Ukraine. Regarding the free state of amino acids, 11 were detected in the raw material of N. damascena, and 9 were found in both N. sativa and N. arvensis. It was found the highest content of L-aspartic acid, specifically 50.359 mg/g in N. damascena (cultivar “Rizdvyana zirochka”), 33.816 mg/g in N. sativa (cultivar “Faraon”), and 31.028 mg/g in N. arvensis. It was revealed that L-leucine, L-valine, and L-tyrosine dominated among the essential amino acids detected in the free state in the seeds of all studied samples. L-glycine and L-proline had the highest amounts among the semiessential amino acids, while L-aspartic acid, L-glutamic acid, and L-phenylalanine are predominant in the nonessential group. Some of the detected in the Nigella sp. amino acids possess significant therapeutic potential.