Carotene and novel apocarotenoid concentrations in orange-fleshed Cucumis melo melons: determinations of ß-carotene bioaccessibility and bioavailability.

Muskmelons, both cantaloupe (Cucumis melo Reticulatus Group) and orange-fleshed honeydew (C. melo Inodorus Group), a cross between orange-fleshed cantaloupe and green-fleshed honeydew, are excellent sources of ß-carotene. Although ß-carotene from melon is an important dietary antioxidant and precursor of vitamin A, its bioaccessibility/bioavailability is unknown. We compared ß-carotene concentrations from previously frozen orange-fleshed honeydew and cantaloupe melons grown under the same glasshouse conditions, and from freshly harvested field-grown, orange-fleshed honeydew melon to determine ß-carotene bioaccessibility/bioavailability, concentrations of novel ß-apocarotenals, and chromoplast structure of orange-fleshed honeydew melon. ß-Carotene and ß-apocarotenal concentrations were determined by HPLC and/or HPLC-MS, ß-carotene bioaccessibility/bioavailability was determined by in vitro digestion and Caco-2 cell uptake, and chromoplast structure was determined by electron microscopy. The average ß-carotene concentrations (µg/g dry weight) for the orange-fleshed honeydew and cantaloupe were 242.8 and 176.3 respectively. The average dry weights per gram of wet weight of orange-fleshed honeydew and cantaloupe were 0.094 g and 0.071 g, respectively. The bioaccessibility of field-grown orange-fleshed honeydew melons was determined to be 3.2 ± 0.3%, bioavailability in Caco-2 cells was about 11%, and chromoplast structure from orange-fleshed honeydew melons was globular (as opposed to crystalline) in nature. We detected ß-apo-8'-, ß-apo-10', ß-apo-12'-, and ß-apo-14'-carotenals and ß-apo-13-carotenone in orange-fleshed melons (at a level of 1-2% of total ß-carotene). Orange-fleshed honeydew melon fruit had higher amounts of ß-carotene than cantaloupe. The bioaccessibility/bioavailability of ß-carotene from orange-fleshed melons was comparable to that from carrot (Daucus carota).