Aspartic Acid Racemization Method for Age Estimation in Human Tissues: A Review

The amino acid racemization is a chemical reaction process that depends on the property change of proteins in the organism. There is change in the concentration of L-and D-amino acids in during life and after death, as well. This change leads to the relationship with aging process. Aspartic acid (Asp) is non-essential amino acid  which  is  commonly  utilized  on  racemization  because  it  has  most  rapidly accumulated of D-aspartic acids of all amino acids. Therefore, aging is related to the  interconversion  of  amino  acids,  which  is   a  useful  tool  for  age  estimation  in forensic science. Aspartic acid racemization can occur in many human structures e.g. teeth, bone, articular cartilage, intervertebral disc, yellow ligament, skin, lung parenchyma, aorta, and eye-lens. Additionally, the relationship between aspartic acid racemization and age can be used for investigation of protein turnover and pathological diseases. There are different aspartic acid preparation methods which obtain  different  results.  In  this  review,  we  describe  aspartic  acid  racemization method,  several  factors  of  racemization,  application  of  racemization  for  age estimation including several preparation methods based on racemization in both teeth and bones.