Uric acid

The structure of the ureate anion (the anion of uric acid) is:

It is a minor end-product of nitrogen metabolism in the human body (the main product being urea), and is found in small amounts in urine. In some other animals, such as birds and reptiles, it is the main end-product, and is excreted in faeces. The high nitrogen content of uric acid is why guano is so valuable as a fertiliser in agriculture.

In human blood, uric acid concentrations between 3.6 and 8.3 mg/dL are considered normal by the American Medical Association, although significantly lower levels are common in vegetarians.

The disease gout in humans is associated with abnormal levels of uric acid in the system. Saturation of uric acid in the human blood stream may result in one form of kidney stones when the acid crystalizes into solid inside the kidney. A percentage of gout patients eventually get uric kidney stones.

see also: xanthine oxidase