Piperonyl butoxide (PBO) is a pale yellow to light brown liquid[1] organic compound used as a synergist component of pesticide formulations. That is, despite having no pesticidal activity of its own, it enhances the potency of certain pesticides such as carbamates, pyrethrins, pyrethroids, and rotenone.[2] It is a semisynthetic derivative of safrole.[3]