Watermelon (Citrullus vulgaris) is an important vegetable  with an annual production of approximately 90 million tons. While watermelon contain more than 90% water with several health promoting compounds such as carotenoids, amino acids including L-citrulline, arginine and glutathione as well as sugars. L-citrulline is a metabolic intermediate, especially in the urea cycle, and is important amino acid, a product of the NO cycle and precursor for arginine. Furthermore, L-citrulline is also reported as an efficient hydroxyl radical scavenger. Currently, free plasma citrulline is measured as part of an amino acid analysis which is expensive. Reported HPLC method for the determination of L-citrulline and sugars involves post-column color development. On the other hand, quantification of sugars needs refractive index detector. In addition, samples should be prepared separately for the measurement of L-citrulline and sugars. These methods are tedious and detection at visible region may not be sensitive as compared to ultra-violet region. Therefore, developing a simultaneous method to identify and quantify L-citrulline and sugars from watermelon sample is warranted. In the present study, lyophilized watermelon sample (30-50mg) was extracted with deuterium oxide (D2O) and quantitatively determined by 1H NMR spectra. An external coaxial glass tube containing 60 �L of known concentration of 3-(trimethylsilyl) propionic-(2,2,3,3-d4) acid sodium salt (TSP) solution in D2O  was used as a quantitative reference. The levels of L-citrulline and sugars were measured less than 5 min. The developed rapid quantitation method can be used widely for confirmation and rapid quantitation of L-citrulline in biological samples. This project is based upon work supported by the USDA-NIFA # 2010-34402-20875 'Designing Foods for Health' through the VFIC and State funding � 2012-124801 Vegetable & Fruit Improvement Center-TX State Appropriation.

Simultaneous quantitation and identification of L-citrulline and sugars in watermelon samples using <sup>1</sup>H NMR

246th National Meeting (2013)

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Simultaneous quantitation and identification of L-citrulline and sugars in watermelon samples using 1H NMR

Simultaneous quantitation and identification of L-citrulline and sugars in watermelon samples using ¹H NMR