Amino acid composition of the ethanolic extractives of 31 species of marine red algae were examined by means of amino acid analyzer. Besides common amino acids, peculiar compounds including gigartinine, methionine sulfoxide and citrullinylarginine were also determined (Table 2).
Citrulline was observed to be widely distributed in red algae abundantly. Algae belonging to Grateloupiaceae were generally rich in citrullinylarginine. Gigartinine was a domiant amino acid in many species of Gracilariaceae, Grateloupiaceae and Phyllophoraceae algae. In Polysiphonia spp., the level of proline was remarkably high and took up about a half of amino acids and ammonia nitrogen.
In the free amino acid composition, a few dominant amino acids appeared in many species of algae examined and occupied the greater part of amino acid nitrogen (Table 3).
Aminosulfonic acids in 21 species of test specimens were examined by paper chromatography. Taurine was detected in 20 species, D-glyceryltaurine in 4, homotaurine in 4, D-cysteinolic acid in 3, d-2-hydroxy-3-aminopropane sulfonic acid in 2, N-monomethyltaurine and N, N-dimethyltaurine in 1, respectively (Table 4).