Antioxidant activities and phytochemicals of polar, semi-polar, and nonpolar extracts of used and unused parts of Carica papaya fruit
Introduction
Carica papaya L. ‘Calina’ is well-known for its edible and nutritional fruit. The plant is highly cultivated in tropical countries for its economic value. Papaya fruit is rich of nutritional components, such as Ca2+, vitamins, protein, sugars, secondary metabolites, and volatile compounds (Almora et al., 2004; de Oliveira and Vitória, 2011; López-Martínez et al., 2015; Rivera-Pastrana et al., 2010; Thaipong et al., 2006). The type and amount of bio compounds are very dependent on the variety, planting conditions, and ripening stages (de Oliveira and Vitória, 2011). It is common for people to only consume the flesh part of papaya fruit, meanwhile, other components, such as flesh and seed, are considered as waste products. The customer behavior of dicing papaya could provide 47% of unused chunks and only 53% of final product (Sagar et al., 2018).
Interestingly, many studies have reported the existence of natural bioactive ingredients, also known as phytochemicals, in the leftover parts of papaya. These compounds, including polyphenols, flavonoids, and tannins, are closely related to the health-promoting effects of papaya (Ikram et al., 2015). Additionally, an ethnopharmacological study on medicinal plants in South East Asia showed that the whole parts of papaya plants benefit in various health conditions, such as menstrual disorders, recovery after pregnancy, and uterine cancer (De Boer and Cotingting, 2014).
The current experiment aimed to evaluate the antioxidant activity, total phenolic content and total flavonoid content of used (flesh) and unused parts of papaya fruit (peel and seed). These papaya parts were extracted consecutively using three different polarity solvents and afterward being evaluated with antioxidant in-vitro tests. The extraction method applied was able to categorize phytochemicals into their polarity groups and to recognize their roles as antioxidant agents. Ultimately, investigations on the health benefit of unused parts of papaya fruit could improve their usage, reduce food waste, and contribute toward economic returns.
Section snippets
Materials
Papaya fruits were collected in October 2018 from a local plantation in Tangerang-Banten, Indonesia. The fruits were green color and ripening on tree, and stored for four days which they started to turn yellow. Afterward, the fruits were cleaned and separated as peel, flesh, and seed (Fig. 1), followed by cutting and drying process in a drying cabinet (40–42 °C) for three days and later grounded into powders with a hammer mill. The powders were then sifted with a sieve 20 Mesh and stored in a
Antioxidant activity of papaya extracts
The antioxidant strength of extract is classified as weak (AAI < 0.5), moderate (AAI 0.5–1.0), strong (AAI 1.0–2.0), and very strong (AAI > 2.0) (Scherer and Godoy, 2009). The AAIs of extracts and the standard compound are shown in Fig. 3.
The DPPH method highlighted a very strong radical scavenging of all extracts tested, except the ethyl acetate extract of papaya peel (PE2). Interestingly, the ethanol extract of papaya seed (SE3) presented a higher AAI than ascorbic acid, which reflected its
Discussion
The plant papaya has carried a long history in traditional medicine, especially in Asia. In the current study, the antioxidant activities of the extracts of papaya peel, flesh, and seed were determined using DPPH and CUPRAC assays. Antioxidant activities of extracts were calculated as AAI, a universal index for antioxidant activity comparison. The AAI value would remain similar in the analysis using various concentrations of radical solutions. Meanwhile, concentration required to obtain a 50%
Conclusion
The unused parts (peel and seed) of papaya fruit showed stronger antioxidant activities and higher phytochemicals content than its used part (flesh). Therefore, it could be concluded that analyzed parts of papaya fruit had significant potencies to be explored as natural antioxidants. Phenolic compounds and flavonoids were quantified in all extracts, but their total contents were not the only factor contributing to antioxidant activities.
Funding
This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.
Declaration of competing interests
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgement
The authors appreciate the authorities of School of Pharmacy, Bandung Institute of Technology for accommodating the required facilities to conduct this research.
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