Citric acid-13C2 is a 13C-labeled form of citric acid. Citric acid serves as a preservative and food additive. It induces apoptosis in HaCaT cells and causes cell cycle arrest at the G2/M and S phases. Additionally, citric acid contributes to liver oxidative damage by reducing antioxidant enzyme activity. It also functions as an acidulant, emulsifier, chelating agent, and buffer, with extensive applications across multiple industries.