Identification and quantification of flavonoids in Carica papaya leaf and peroxynitritescavenging 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 3rutinoside, myricetin 3-rhamnoside, kaempferol 3-rutinoside, quercetin, and kaempferol. All of the substances exhibited potent activities on peroxynitrite scavenging (IC50 <= 4.15 mu mol/ L), which were stronger than the positive control, L-penicillamine (6.90 mmol/ 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.