Oxalic Acid

Oxalate is a common constituent of many plant species. Some crop plants accumulate high levels of this dicarboxylic acid anion (oxalate). Depending on the species, oxalate accumulates primarily as soluble oxalate, insoluble calcium oxalate, or a combination of these two forms. Oxalate, because of possessing negative charges, has high affi nity for minerals, such as calcium, magnesium, and zinc. Through ionic interaction it binds to these metal ions (Fig. 1) and affects their availability and metabolism (Fig. 1) . The high capacity of soluble oxalate to bind to calcium in blood serum can lead to acute intoxication in humans and cattle if ingested in high doses. On the other hand, a high oxalate uptake from the diet is also thought to play a role in hyperoxaluria, which can lead to the formation of calcium oxalate in kidneys (commonly called kidney stones). High levels of oxalate in the blood have also been reported to be associated with arthritis. Furthermore, metal ions like cadmiumincorporated calcium oxalate crystals are also responsible for the heavy metal mediated health risks.