Xanthoprotein Reaction

Xanthoprotein reaction (method for the determination of cyclic amino acids) is a method for determining cyclic amino acids in proteins, based on their ability to give a yellow color in the presence of concentrated nitric acid. The method is based on the ability of tryptophan, tyrosine and phenylalanine, which are part of proteins, to decompose when heated in the presence of nitric acid, resulting in the formation of colored compounds. The xanthoprotein reaction can be used not only for the determination of cyclic acids, but also for the detection of proteins in solutions.

The xanthoprotein (xanthone) reaction is a method for determining the content of cyclic amino acids in proteins and other organic compounds. It is based on the ability of certain amino acids, such as tryptophan and tyrosine, to produce a yellow or orange color when treated with concentrated nitric acid. This method was discovered in 1913 by the German chemist Otto Neisser and named after him.

The xanthoprotein reaction is used to determine the level of proteins in various biological fluids, such as blood serum, urine and saliva. It is also used in the analysis of foods and drugs for the presence of protein.

To carry out the xanthoprotein reaction, a sample of the analyte is mixed with concentrated nitric acid and heated to boiling. A small amount of alkali is then added to neutralize the acid. The resulting yellow precipitate contains cyclic amino acids.

This method is highly sensitive and allows the determination of protein content in very small quantities. However, it has some limitations, such as the need to use concentrated nitric acid, which can be hazardous to health. In addition, the xanthoprote reaction is not specific for all types of proteins and may give false-positive results in the presence of some other compounds.

Despite these limitations, the xanthoprotein reaction remains an important method for protein analysis and continues to be used in various fields of science and industry.