Sterigmatocystine-13C18 is 13C labeled Sterigmatocystine (HY-N6725). Sterigmatocystine is a precursor of aflatoxins and a mycotoxin produced by common mold strains from Aspergillus versicolor[1][2]. Sterigmatocystine, a inhibitor of G1 Phase and DNA synthesis, is used to inhibit p21 activity. Sterigmatocystine has teratogenic, and carcinogenic effects in animals[3].