title: A metabolomics approach to identify and quantify the phytochemicals in watermelons by quantitative (1)HNMR.
abstract: Watermelon (Citrullus vulgaris) contains many health-promoting compounds, such as ascorbic acid, carotenoids, phenolic acids and amino acids including l-citrulline, arginine, and glutathione. Reported HPLC method for quantification of l-citrulline and sugars in watermelon involves, time-consuming sample preparation, post-column color development and detection with fluorescence and refractive index detectors. The present study describes development of a method to identify and quantify amino acids and sugars simultaneously from watermelon samples using quantitative proton NMR. Lyophilized watermelon samples (30-50mg) were extracted with deuterium oxide (D2O) by sonication and the centrifuged extract was directly used for quantification and identification with (1)HNMR. An external coaxial insert containing a 65µL of 0.012% 3-(trimethylsilyl) propionic-(2,2,3,3-d4) acid sodium salt (TSP-d4) in D2O was used as a quantitative reference. The levels of l-citrulline and sugars were measured in less than 6min. This rapid quantitation method was validated for specificity, linearity, accuracy, precision, reproducibility, and robustness. The limit of detection for l-citrulline was 38µg/mL and the limit of quantification was 71µg/mL; for sugars, the limits were 59-94µg/mL and 120µg/mL, respectively. This method can be used widely for confirmation and rapid quantitation of multiple compounds in large number of biological or breeding samples for routine analysis.
authors.affiliation: Vegetable and Fruit Improvement Center, Department of Horticultural Sciences, Texas A&M University, 1500 Research Parkway, Suite A120, College Station, TX 77845-2119, USA. Electronic address: gkjp@tamu.edu.
authors.forename: G K
authors.initials: GK
authors.lastname: Jayaprakasha
authors.affiliation: Vegetable and Fruit Improvement Center, Department of Horticultural Sciences, Texas A&M University, 1500 Research Parkway, Suite A120, College Station, TX 77845-2119, USA. Electronic address: b-patil@tamu.edu.
authors.forename: Bhimanagouda S
authors.initials: BS
authors.lastname: Patil
mesh_terms: D002956:Citrulline; D029773:Citrullus; D009682:Magnetic Resonance Spectroscopy; D055432:Metabolomics; D064209:Phytochemicals; D015203:Reproducibility of Results
chemical_list: D064209:Phytochemicals; D002956:Citrulline
keywords: Amino acids; Citrullus vulgaris; Quantitation; Sugars; l-Citrulline; qNMR