An isolated phycobilin for use in a method for prophylaxis or treatment of a medical condition selected from:(i) ischemic heart disease associated with or linked to an NADPH oxidase activity；(ii) stroke associated with or linked to an NADPH oxidase activity；(iii) ischemia-reperfusion damage associated with or linked to an NADPH oxidase activity in connection with myocardial infarction； and(iv) ischemia-reperfusion damage associated with or linked to an NADPH oxidase activity in connection with transplant rejection；the method comprising the step of administering an isolated phycobilin to a subject in a prophylactically or therapeutically effective amount for prophylaxis or treatment of the medical condition.
