HC Toxin is a cyclic tetrapeptide first isolated from H. carbonum (now C. carbonum), a pathogen of maize. It is a reversible inhibitor of histone deacetylases (HDACs) (IC₅₀ = 30 nM). Through its effects on HDACs, HC toxin has been shown to up-regulate the expression of 15-lipoxygenase-1 in colorectal cancer cells and induce fetal hemoglobin in human primary erythroid cells