Nutritional relevance of papaya carotenoids considering carotenoid profiles, chromoplast morphology, and ultrastructure

Similarities among nutritionally relevant carotenoid profiles in red- and yellow-fleshed papaya (Carica papaya L.) cultivars were revealed using liquid chromatography coupled to mass spectrometry. Differences were observed mainly in lycopene content. Where yellow papayas contain only trace amounts of lycopene, it is the predominant carotenoid in red papayas. Chromoplast morphology and ultrastructure of red- and yellow-fleshed papayas were investigated using light and transmission electron microscopy. Carotenoids in yellow papaya were deposited in tubular plastids, while crystalloid substructures in red papaya chromoplasts were associated with lycopene accumulation. Carotenoid deposition may be relevant to its bioavailability. Therefore, this parameter was compared among papaya, carrot, and tomato using 16 healthy human subjects for a randomized crossover study. Test meals were adjusted in order to deliver equal amounts of β‑carotene and lycopene. Triacylglycerol-rich lipoprotein fractions were analyzed for 9.5 hours after test meal consumption. β‑Carotene of papayas was approximately three times more bioavailable than that of carrots and tomatoes. Moreover, lycopene bioavailability in papayas was approximately 2.6 times higher than that of tomatoes. Bioavailability of β‑cryptoxanthin from papayas was higher when compared with the other papaya carotenoids, β‑carotene and lycopene, respectively 2.9 and 2.3 times higher. Liquid-crystalline deposition of β‑carotene and the storage of lycopene in very small crystalloids in papayas may play an important role in improving the bioavailability of such carotenoids when compared with other deposition forms.