Homogentisic acid, also known as HGA, is a chemical compound commonly found in the human body. This substance is produced during the breakdown of amino acids such as phenylalanine and tyrosine, which are used by the body to build proteins. Homogentisic acid is also known as oxidized alkylated polyphenol (OAP) and 2,5-Dihydroxyphenylacetic acid (DOPAC) in different contexts. It is a metabolic waste product that accumulates in certain individuals causing a condition called alkaptonuria. In other literature sources, it is referred to as Alkapton or Alcapton in the ancient texts. This chemical compound is also closely associated with a genetic disorder called ochronosis.