Determination and Quantification of Amino Acids in Vegetables By HPLC Fluorescence Detection

Amino acids act as building blocks for proteins, precursor for hormones, neurotransmitters, and play an important role in a plethora of metabolic pathways. They are not only essential for human health but also play an important role in plants to synthesize proteins, aid in protection as they produce in response to stress.  Additionally, they are activators and precursors to phytohormones among other important functions. A method has been developed for the analysis of amino acids in vegetables by HPLC using fluorescence detector. The current method was optimized to determine the free amino acids content in beetroot, watermelon and kale. Fresh vegetables were processed using kitchen juicer, centrifuged, filtered and analyzed by pre-column derivatization. Derivatization was carried out at room temperature for two minutes with ortho-phthalaldehyde reagent. A XSelect HSS T3 column with 3.5µm particle size (250 X 4.6mm) was used with an oven temperature at 30°C.  The detector excitation and emission wavelengths were set at 340 and 455nm respectively. A total of 19 amino acids were identified with the major amino acids L-citrulline (1580.7±28.1µg g^-1), histidine (1112.1±29.8µg g^-1 and glutamine (1078.4±0.7µg g^-1) found in watermelon, beet and kale respectively. The developed method is found to be a simple and reliable for the analysis of amino acids using fluorescence detection. The present method involves simplified sample preparation and a rapid derivatization procedure.