Antioxidant and anti-inflammatory properties of papaya (Carica papaya) fruits were evaluated to provide comprehensive information associated with the bioactive compounds. 'Tainung No. 2' papaya fruits, cultivated in a greenhouse, Korea, were harvested at unripe and ripe stages and then divided into seed and peel-pulp. Total phenolic and flavonoid contents were determined using spectrophotometry, and individual phenolic compounds were relatively quantified by HPLC-DAD and fifteen standards. Antioxidant activities were measured using four assays: DPPH (2,2-diphenyl-1-picrylhydrazyl) and ABTS (2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid)) scavenging activities, inhibition of lipid peroxidation, and FRAP (ferric reducing antioxidant power). Anti-inflammatory activities were measured by the regulation of NF-κB signaling pathways with the measurements of ROS and NO productions as the degree of oxidative stress. Total phenol contents increased in seed and peel-pulp extracts during ripening; flavonoid contents increased only in seed extracts. Total phenolic contents were associated with ABTS radical scavenging activity and FRAP. Of fifteen phenolic compounds, chlorogenic acid, cynarin, eupatorine, neochlorogenic acid, and vicenin II were identified among papaya extracts. ROS and NO productions were inhibited in papaya extracts. Especially, NO productions were inhibited higher in ripe seed extracts than in other extracts, which would be associated with the suppression of NF-κB activation and iNOS expression. These results suggest that papaya fruit extracts, including seeds, peels, and pulps, could be potential raw materials for functional foods.
Keywords: ABTS; FRAP; NF-κB; flavonoid; phenolic; ripening; seed.