PHYSIOLOGICAL AND GENETIC BASIS OF POSTHARVEST QUALITY AND PHYTONUTRIENT CONTENT OF FRUITS AND VEGETABLES
Title: WATERMELONS AND HEALTH
Submitted to: Acta Horticulturae
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 30, 2005
Publication Date: January 15, 2007
Citation: Perkins Veazie, P.M., Collins, J.K., Clevidence, B.A., Wu, G. 2007. Watermelons and health. Acta Horticulturae. 731:121-127.
Interpretive Summary: The content of lycopene and citrulline has been studied extensively for many varieties and types of watermelons. Lycopene, a red pigment found to be beneficial in preventing some types of heart disease and cancer, is found mostly in red-fleshed varieties. The amino acids citrulline and arginine have many metabolic functions in humans, including vasodilation. These amino acids are found in all watermelons and are present in rind, peel, and flesh. Lycopene, arginine, and citrulline were found in plasma after watermelon consumption, with levels dependent on serving size. Work on watermelon shows that this fruit can be an important source of human wellness compounds.
In addition to the nutrients vitamin A, C and potassium, watermelon (Citrullus lanatus) also contains lycopene, citrulline, and arginine. Lycopene is the pigment that imparts red color to some fruits, most notably tomato and watermelon. It is also a highly efficient oxygen radical scavenger and has been implicated in human studies as providing protection against cardiovascular disease and some cancers, particularly that of the prostate. Watermelons contain as much or more lycopene than tomatoes but have been little studied. Over the last six years, we have conducted numerous studies with watermelon to evaluate germplasm, storage and minimal processing effects on lycopene levels. Additionally, we conducted a cooperative human clinical study with watermelon and tomato juice to determine lycopene uptake in humans. Assays of human plasma after watermelon ingestion indicated that lycopene was as efficiently obtained from watermelon juice as from tomato juice. Citrulline and arginine are amino acids found in watermelon and are major components of the human nitrous oxide system and help regulate many biochemical processes. Citrulline lacks biological importance on its own but is transformed by the human body into arginine. Arginine is readily converted into the nitric oxide pathway to help in vasodilation and overall cardiovascular health. Our recent work with citrulline identified that it is present in watermelons in the peel, rind, and flesh. Following the lycopene human clinical trial we measured the citrulline levels in the human plasma from the subjects who ingested watermelon juice. Plasma levels of citrulline were highest in subjects who consumed six cups of watermelon juice per day. Further studies with these unique compounds found in watermelon are ongoing.