(-)-Epicatechin-13C3 ((-)-Epicatechol-13C3) is 13C labeled (-)-Epicatechin. (-)-Epicatechin inhibits cyclooxygenase-1 (COX-1) with an IC50 of 3.2 µM. (-)-Epicatechin inhibits the IL-1beta-induced expression of iNOS by blocking the nuclear localization of the p65 subunit of NF-kappaB.