Caffeicacid-13C3 is an isotopically enriched form of caffeicacid that is intended for use as an internal standard for the quantification of caffeicacid by GC- or LC-MS. Caffeicacid is an inhibitor of 5-LO , with IC50 values of 3.7-72 μM, and 12-LO, with IC50 values of 5.1-30 μM.