Abstract − Compositional differences in flavonoids are varied in the big family of Compositae. By summarizing our previous analytical studies and other scientific evidences, new strategy will be possible to further analyze flavonoids and utilize them for human health. The HPLC analytical method has been established in terms of linearity, sensitivity, accuracy, and precision. Herbs of the family of Compositae have considerable amounts of peroxynitrite (ONOO− )-scavenging effects and their phenolic substances. These effects may contribute to the prevention of disease associated with excess production of ONOO− , depending on the high content of flavonoid substances. Keywords − Compositae, Flavonoids, Phenolic substance, HPLC analysis, Peroxynitrite