DL-Isocitric acid- 13 C 4 (trisodium salt) is a 13 C labeled DL-Isocitric acid (trisodium salt). DL-Isocitric acid trisodium salt is an endogenous metabolite. DL-Isocitric acid trisodium salt is a substrate in the citric acid cycle. DL-Isocitric acid trisodium salt can be used as a marker for determining the composition of isocitrates in fruit products, including fruit juices.