O-Methylsterigmatocystin is a xanthone isolated from several species of Aspergillus and Chaetomium. O-Methylsterigmatocystin is structurally related to the aflatoxins and, while it is considered mutagenic, teratogenic and carcinogenic, it is less widespread and potent than the aflatoxins. Research on this metabolite has largely focused on its genetic and phenotypic relationship to aflatoxins.