Abstract: 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.

Abstract: Processes for isolating substantially pure natural L-&bgr;-3-indolylalanine (L-&bgr;-3) from a mixture of amino acids, such as a protein hydrolysate. A protein hydrolysate, for example of casein or soy protein, is passed over a polymeric resin attractive to aromatic amino acids but not attractive to aliphatic amino acids. The aromatic amino acids are retained on the resin while the aliphatic amino acids pass over the resin and are collected. The resin is then washed to displace any residual aliphatic acids which may be physically associated with but not bound to the resin. Thereafter, the resin is eluted with a dilute acid to displace L-phenylalanine and L-tyrosine and provide a solution thereof while allowing L-&bgr;-3 to be retained on the resin. The resin is then further eluted with a dilute base to displace L-&bgr;-3 from the resin and provide a solution of L-&bgr;-3. Substantially pure natural L-&bgr;-3 is recoverable from this solution.