Abstract:
The literature synopsis consists of a discussion of (a) the theory of some isolation and analytical methods, (b) the role of toxic amino acids which occur in the genus Acacia and (c) the biosynthesis of some of the non-protein amino acids in the genus. The free amino acids which occur in the leaves of Acacia mellifera subsp. detinens are not affected by oxidation, with 15% (v/v) hydrogen peroxide at room temperature, hydrolysis with 3 mol. dm hydrochloric acid at 100°C and hydrolysis with 5% (m/v) barium hydroxide at 100°C. The free amino acids that occur in the leaves, flowers and seeds of the plant were compared. A larger variety of amino acids occurs in the flowers and seeds of the plant than in its leaves. A good separation of the free amino acids of the leaves was obtained with an ammonium formate buffer in a Dowex 50 ion exchange resin column. Sephadex columns were used for further purification of the amino acids. Alanine, pipecolic acid and 4-hydroxypipecolic acid were isolated in pure crystalline form from the leaves of the plant. Their chemical structures were confirmed by mass spectroscopy, nuclear magnetic resonance spectroscopy, and in the case of alanine also with automatic amino acid analysis. Aspartic acid, 2-amino-3-acetylaminopropionic acid, 4-aminobutyric acid, 2-amino-3-ureidopropionic acid, glycine, glutamic acid, 5-hidroxypipecolic acid, lysine, serine and valine were identified by paper and thin layer chromatography only. The biosynthesis of some of the amino acids were examined by means of 14 C-labelled precursors. Pipecolic acid is biosynthesized from lysine. 4-Hydroxypipecolic acid is derived from pipecolic acid by hydroxylation.
