4-hydroxy Alternariol is a metabolite of the mycotoxin alternariol formed through cytochrome P450 (CYP450) metabolism. It increases reactive oxygen species (ROS) in KYSE510 human esophageal cells by 701% compared to control. 4-hydroxy Alternariol increases topoisomerase IIβ-DNA complexes by 208% compared to control in an ICE assay but does not induce DNA damage in KYSE510 cells. It completely inhibits topoisomerase IIα activity at a concentration of 25 μM under cell-free conditions.