Exploring the nutritional potential of Carica papaya Linn cultivars

Abstract

Carica papaya, commonly known as papaya or paw paw, is widely cultivated for its sweet, ripe edible fruits. However, papaya is also known for its health uses in some non-western cultures where green fruits and leaves are also eaten cooked as well as raw. This research project has looked at phytochemicals (carotenoids (provitamin A active compounds), polyphenols, ascorbic acid, and vitamin E) and antioxidant capacity (ORAC assay and total phenolic content) of fruit pulp, fruit peel and leaves from commercially available Australian papaya cultivars. Analysis was undertaken at different stages of fruit ripeness and leaf growth to understand the impact on nutritional quality and potential health properties. In addition, the release/bioaccessibility of the main phytochemicals was assessed as an initial measure to predict their potential bioavailability using an in vitro digestion procedure. Among cultivars, red fleshed papaya fruits exhibited the highest phytochemical values. Mid mature and/or fully ripen fruits gave the highest antioxidant capacities as well as ascorbic acid and carotenoid content. Ascorbic acid content ranged from 37.0-58.5 mg/100 g FW with large variations between cultivars and an increase as the fruits ripen. Major carotenoids found in red-fleshed papaya were b-carotene, b-cryptoxanthin, and lycopene with lycopene representing 42-58% of the total carotenoids. However, lycopene was undetectable in the yellow-fleshed cultivar. Leaves were found to exhibit the highest ORAC and total phenolic content (young and mature; ORAC: 93-185 mM trolox equivalents/g FW; total phenolic content: 148-210 mg gallic acid equivalents/100g FW) compared to the peels and pulps. Overall, the highest antioxidant capacity, ascorbic acid and polyphenols could be found in papaya leaves followed by peels and pulp. Vitamin E was below the limit of quantification in all samples. Cooking of the leaves and unripe fruit resulted in a significant reduction of ascorbic acid and antioxidant capacity. In addition, in vitro digestion clearly demonstrated that the major papaya phytochemicals are bioaccessible from the pulp as well as the leaf matrix. Heat treatment (boiling) may enhance the bioaccessibility of TPC papaya fruits and leaves. The findings of this study showed that the phytochemical composition and antioxidant capacity varied across different papaya cultivars, maturity stages and plant parts affecting the nutritional value of this important tropical fruit.