An unstable anthraquinone was isolated from hairy root cultures of Sesamum indicum after preventing light throughout all experimental procedures. The structure of the (Z)-isomer of a previously isolated anthraquinone was determined to be 2-[(Z)-4-methylpenta-1,3-dien-1-yl]anthraquinone by spectroscopic methods. This compound was readily isomerized to the known (E)-isomer under light.
