Citric acid-2,4-13C2 is the 13C-labeled Citric acid (HY-N1428). Citric acid is a natural preservative and food tartness enhancer. Citric acid induces apoptosis and cell cycle arrest at G2/M phase and S phase in HaCaT cells. Citric acid cause oxidative damage of the liver by means of the decrease of antioxidative enzyme activities. Citric acid is also an acidulant, emulsifier, sequestrant and buffering agent widely used across many industries[1][2][3][4].