Determination of the Polyamine Content for the Ethanolic Extract of Quinoa Food with the Developed On-line SE-HPLC-Bradford Methodology

Abstract

Polyamines are essential for all types of cell growth, proliferation, and maintenance of life. Quinoa, a Chenopodioideae and the most important food source for the Incas in the Southern USA, is a nutritious astronaut food, rich in polyamines. In this study, natural polyamines (spermidine, spermine, putrescine, cadaverine, γ-amino-butyric acid, agmatine, arginine, N-acetyl-L-cysteine) isolated from the ethanolic extract of quinoa were detected by SE-HPLC-DAD-UV system combined with a simultaneous syringe flow system. The potential of Coomassie Brilliant Blue-G-250 dye solution (Bradford reagent) (70 mg / L) to interact with basic amino acids ((lysine, arginine, histidine) could also bind natural polyamines in quinoa. The concentration of polyamine bound with the Bradford reagent was  measured simultaneously with an optimized on-line SE-HPLC-Bradford methodology (Agilent 1100 serials HPLC-DAD-UV combined with size exclusion column (Agilent Zorbax G-450, 9.4 mm × 250 mm i.d., 6 μm particle size) and isocratic solvent system (50 mM pH 7 phosphate buffer and 0.2 M KCl (for ionic violence)), 15 min running time, 595 nm UV detection, 229 nm diode array detection, 30°C reaction temperature, 2.5 m polytetrafluoroethylene (PTFE) tubing (0.25 mm i.d.) reaction coil, manager pump flow: 0.5 mL.min^-1, syringe pump flow: 0.3 mL.min^-1). The highest polyamine concentration was γ-amino-butyric acid with 2.7 ng/mL. The % recovery was 98.2 and the linear range was 0.2-5 ng/mL. In triple replicate trials, the mean limits of detection were LOD: 0.25 ng/mL and LOQ:0.83 ng/mL, respectively. The results given with the standard deviations were significant (p < 0.05).