Objective To characterize the types, contents, and peroxynitrite-scavenging activities of flavonoids in the leaf of Carica papaya (C. papaya). Methods Chromatographic and spectroscopic techniques along with high performance liquid chromatography quantitative analysis and peroxynitrite-scavenging assay were performed to isolate and quantify flavonoid compounds in the flavonoid-rich fraction (BuOH fraction) derived from MeOH extract of C. papaya leaves and evaluate their peroxynitrite-scavenging activities. Results Seven flavonoids were isolated from the leaves of C. papaya, including quercetin 3-(2