Identification and quantification of flavonoids in Carica papaya leaf and peroxynitrite-scavenging activity

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 G -rhamnosylrutinoside), kaempferol 3-(2 G -rhamnosylrutinoside), quercetin 3-rutinoside, myricetin 3-rhamnoside, kaempferol 3-rutinoside, quercetin, and kaempferol. All of the substances exhibited potent activities on peroxynitrite scavenging (IC 50 ≤ 4.15 μmol/L), which were stronger than the positive control, l -penicillamine (6.90 μmol/L). The content of kaempferol 3-(2 G -rhamnosylrutinoside) was significantly higher than other identified compounds (123.18 mg/g BuOH fraction and 7.23 mg/g MeOH extract). Conclusions The results of the present study demonstrate the potent antioxidant flavonoids of C. papaya leaf, with kaempferol 3-(2 G -rhamnosylrutinoside) as the major one.