Main content area

A metabolomics approach to identify and quantify the phytochemicals in watermelons by quantitative 1HNMR

Jayaprakasha, G.K., Patil, Bhimanagouda S.
Talanta 2016 v.153 pp. 268-277
Citrullus lanatus var. lanatus, arginine, ascorbic acid, breeding, carotenoids, citrulline, color, detection limit, detectors, deuterium oxide, fluorescence, freeze drying, glutathione, health promotion, high performance liquid chromatography, metabolomics, nuclear magnetic resonance spectroscopy, phenolic acids, phytopharmaceuticals, refractive index, sodium, sonication, watermelons
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 ¹HNMR. 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.