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By Rosalie Marion Bliss
July 1, 2014
Orange-fleshed honeydew melon is a cross between cantaloupe and green-fleshed honeydew. Orange-fleshed honeydew melon is sweeter and stores longer than the typical cantaloupe. To learn more about the melons, U.S. Department of Agriculture (USDA) plant physiologist Gene Lester and his colleagues measured the beta-carotene concentrations in orange-fleshed honeydew and cantaloupe melons grown under the same greenhouse conditions.
Carotenoids such as beta-carotene are also known as provitamin A. Beta-carotene is the most potent precursor of vitamin A for humans, which means the body breaks down beta-carotene into vitamin A.
Lester is with the USDA Agricultural Research Service (ARS) Office of National Programs in Beltsville, Maryland. ARS is USDA's principal intramural scientific research agency.
The team found that orange-fleshed honeydew had significantly higher beta-carotene concentrations than cantaloupe, but the two melon types had similar beta-carotene bioaccessibility. Before the human body can make use of a fruit's nutrients, the nutrients must first be released from the fruit tissues, becoming "bioaccessible," and then the nutrients can be absorbed into the circulation, becoming "bioavailable." This means that both melons appear to be comparable sources of dietary provitamin A for humans, on par with carrots, which are known to be a major source of provitamin A.
When testing orange-fleshed melons, the team also noticed indications of compounds not seen before, so they used more sophisticated instrumentation to show that these compounds were apocarotenoids. This is significant because apocarotenoids are metabolized directly into vitamin A. Previously, the researchers did not know apocarotenoids were in orange-fleshed melons.
Lester's team detected and measured levels of the apocarotenoids beta-apo-13-carotenone, beta-apo-14-carotenal, beta-apo-12-carotenal, beta-apo-10-carotenal, and beta-apo-8-carotenal in the orange-fleshed melons.
Funding support for the study was provided by USDA and by grants from the National Institutes of Health.