Processes for extracting amino acids from mixtures of amino acids, and compositions and mixtures formed therefrom. Applications include isolating natural L--3-indolylalanine (L--3) and providing natural or other amino acid mixtures enriched with the extracted L--3. The source of amino acids may include a natural source, such as enzymatic or other natural protein hydrolysates containing mixtures of free amino acids. The process includes contacting the mixture of amino acids with a resin or hydrophobic substance that is attractive to aromatic amino acids but not attractive to aliphatic amino acids to separate the aromatic amino acids from the rest of the mixture. This contacting may include agitating the mixture and hydrophobic substance to increase contact therebetween. The L--3 may then be separated from the monocylic amino acids by contacting the hydrophobic substance with an acid, and L--3 may be removed from the hydrophobic substance by contact with a base.