4-Azido-L-phenylalanine (p-Azido-L-phenylalanine) is an amino acid derivative that acts as a photoaffinity marker and can be used to detect localized protein environments.

Aminoisobutyric acid is a nonprotein amino acid (is an end product of pyrimidine metabolism) excreted in the urine of about 5% of healthy individuals and high excretion is an autosomal recessive phenotype.

Dried aged bark of a buckthorn, Frangula purshiana (FRANGULA), that contains the anthraquinone EMODIN and cascarosides. It is used as a laxative (CATHARTICS).