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United States Department of Agriculture

Agricultural Research Service

Title: Determination of Citrulline in Watermelon Rind

Authors
item Rimando, Agnes
item Perkins Veazie, Penelope

Submitted to: Journal of Chromatography A
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 2, 2005
Publication Date: May 9, 2005
Citation: Rimando, A.M., Perkins Veazie, P.M. 2005. Determination of citrulline in watermelon rind. Journal of Chromatography A. 1078:196-200.

Interpretive Summary: Citrulline is an amino acid first isolated from watermelon juice. Citrulline has potential antioxidant and vasodilatation roles. The flesh, rind and peel of 14 varieties of watermelon were analyzed for their citrulline content. Among the flesh samples, the highest level of citrulline was found in the seedless Hazera SW1 and Solid Gold, and the seeded Summer Gold varieties. Seeded varieties had slightly less citrulline than the seedless melons. When compared by flesh color, red fleshed melons had less citrulline in flesh or rind than orange or yellow fleshed fruit. On a dry weight basis, the citrulline content of the rind was higher than that of the flesh. Half of a watermelon fruit is edible while the other half, consisting of about 35% rind and 15% peel, goes to waste. From this study, it is shown that the rind contains citrulline in high quantities and is a rich source of an important amino acid and may yield a useful product from an agricultural waste.

Technical Abstract: Watermelon (Citrullus lanatus Schad.) is a natural and rich source of the non-essential amino acid citrulline. Citrulline is used in the nitric oxide system in humans and has potential antioxidant and vasodilatation roles. A method using gas chromatography-mass spectrometry (GC-MS) was developed to separate citrulline from glutamic acid, which co-elute when analyzed by high performance liquid chromatography. Watermelons were analyzed by GC-MS to determine the citrulline content among varieties, types, flesh colors, and tissues. Citrulline content ranged from 3.9 to 28.5 mg/g dry weight (dwt) and was similar between seeded and seedless types (16.6 and 20.3 mg/g dwt, respectively). Red flesh watermelons had slightly less citrulline than the yellow or orange flesh watermelons (7.4, 28.5 and 14.2 mg/g dwt, respectively). Rind contained more citrulline than flesh on a dry weight basis (24.7 and 16.7 mg/g dwt, respectively) but a little less on a fresh weight (fwt) basis (1.3 and 1.9 mg/g fwt, respectively). These results indicate that watermelon rind, an underutilized agricultural waste, offers a source of natural citrulline.

Last Modified: 8/30/2014
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