Carotenoid and Carotenoid Ester Profile and Their Deposition in Plastids in Fruits of New Papaya (Carica papaya L.) Varieties from the Canary Islands

Abstract

The carotenoid profile of non-saponified and saponified extracts of different tissues (pulp and peel) of fruits of three new papaya varieties, Sweet Mary, Alicia, and Eksotika, was characterized for the first time, and almost all carotenoid compounds were quantified. Carotenoids and carotenoid esters were analyzed and characterized using HPLC-photo diode array (PDA-MS with atmospheric pressure chemical ionization with positive ion mode (APCI+) with a C30 reversed-phase column. The carotenoid deposition in collenchyma and chlorenchyma cells of papaya pulp and peel tissues was assessed by optical microscopy, confocal laser scanning microscopy, and transmission electron microscopy. The most abundant carotenoids in the fruit of the three papaya varieties (pulp and peel) were (all-E)-lycopene (230.0–421.2 µg/100 g fresh weight), (all-E)-β-carotene (120.3–233.2 µg/100 g fresh weight), and (all-E)-β-cryptoxanthin laurate (74.4–223.2 µg/100 g fresh weight. Moreover, high concentrations of (all-E)-lutein (922.5–1381.1 µg/100 g fresh weight) and its esters, such as (all-E)-lutein-3-O-myristate and (all-E)-lutein dimyristate, were found in peel extracts. The optical microscopy study of papaya pulps showed that carotenoid deposition in all papaya varieties, including Maradol, was mainly localized close to the cell walls, showing the presence of some crystalloids and round-shaped structures, with different sizes and distribution due to the different carotenoid content among varieties. No crystalloids or globular depositions were found in any of the peel sections, and no remarkable differences were found in the papaya peel microstructure of the different papaya varieties.