Amino acids, fruit acids and polyols of myrobalans

Abstract

The examination of the polyphenols and tannins of the dried fruit of Ter-minalia species (myrobalans) by means of chromatographic methods is briefly summarized. After removal of polyphenols and tannins from an 80% (v/v) aqueous methanolic extract of myrobalans, the remaining constituents are divided into neutral, basic and acidic fractions by ion-exchange chromatography, the amino acids isolated after electrolytic desalting of the basic fraction, and paper chromatographic methods used for the provisional identification of constituents in the 3 fractions. Glucose and sorbitol predominate in the neutral fraction, which also contains about 1% each of fructose and sucrose, a small quantity of gentiobiose and traces of arabinose, maltose, rhamnose and xylose. The range of amino acids is typical of those detected in plant extracts in general, and it is possible that all 18 of these substances occur free in intact plants. In addition to small quantities of phosphoric and succinic acids, a family of related cyclohexanecarboxylic acids has been identified. These include quinic and shikimic acids as major constituents, together with smaller amounts of dihydro- and possibly dehydro-shikimic acids. Tentative evidence for the occurrence of a related ester phosphate is also presented. Dihydro-shikimic acid has not been previously detected in plant material. The nature of the constituent amino acids, fruit acids and polyols is discussed against the background of authenticated plant products. It is suggested that the structurally related cyclohexanecarboxylic acids may be formed by the plant as intermediates of aromatic biosynthesis, leading to the aromatic amino acids and the simple polyphenolic units from which the tannins of the Terminalia species are elaborated.