Folic acid is a water-soluble vitamin B, which is also known as vitamin B9 or folate or pteroylglutamic acid. It is naturally found in leafy vegetables and fruits. It plays an important role in DNA synthesis and acts as a free radical scavenger.Folic acid-(glutamic acid-13C5,15N) is an isotope of vitamin B9 wherein glutamate nitrogen and all the five glutamate carbons are replaced by15N7nitrogen and13C6carbon, respectively.Folic acid-(glutamic acid-13C5,15N) can be used as an analytical standard for data interpretation in specific biological samples.