Antioxidant activities and phytochemicals of polar, semi-polar, and nonpolar extracts of used and unused parts of Carica papaya fruit

Papaya fruit contains phytochemicals, such as polyphenols and flavonoids. These compounds are closely related to its health-promoting effects. The aim of present study was to evaluate the antioxidant activities of the used part (flesh) and unused part (peel and seed) of papaya. Furthermore, the influence of total phenolic (TPC) and flavonoid content (TFC) on the antioxidant activities were analyzed. Extraction was conducted by reflux method with three increasing polarity solvents consecutively. Afterwards, the antioxidant actions were evaluated by 2,2–diphenyl-1-picrylhydrazil (DPPH) and Cupric Reducing Antioxidant Capacity (CUPRAC) assays. The results were presented as Antioxidant Activity Index (AAI) and in the range of 1.91–47.89 for DPPH and 1.28–3.59 for CUPRAC which indicated strong and very strong antioxidant activities. The ethanol extract of papaya seed had greater activity than the reference compound. Meanwhile, phenolic compounds and flavonoids were quantified using the colorimetric method. The highest TPC and TFC were obtained from the n-hexane extract of papaya seed (39.26 g gallic acid equivalent/100 g extract) and the ethyl acetate extract of papaya flesh (57.57 g quercetin equivalent/100 g extract), respectively. Moreover, the correlations between phytochemicals and antioxidant activity were analyzed statistically and resulting insignificant and negative Pearson’s correlations in most samples. Thus, TPC and TFC were not the major factors contributing to antioxidant actions. The present study showed that both used and unused parts of papaya fruit had natural antioxidant potencies. •Antioxidant activity from papaya peel and seed were stronger than its flesh.•The n-hexane extract of papaya seed had the highest total phenolic content.•The ethyl acetate extract of papaya peel had the highest total flavonoid content.•Quantitative and qualitative of phytochemicals contributed to antioxidant activity.