Aszonalenin is a complex benzodiazepine metabolite isolated from Aspergillus zonatus by Kimura and co-workers at Tottori University, Japan in 1982. Structurally, aszonalenin is formed from an intra-molecular ring closure of anthranilic acid and L-tryptophan to form the pyrrole, followed by prenylation. At high concentration aszonalenin has been shown to induce an abnormal second cleavage of sea urchin embryos but its pharmacology has otherwise received scant attention.