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Abstract

Tryptophan is an essential amino acid that is necessary for the biosynthesis of neurotransmitters including serotonin and melatonin via two biochemical pathways. However, further research into the role of tryptophan and its derivatives in biological systems has been limited as these compounds are mostly diverse in terms of their chemical properties resulting in the need of more than one analytical technique to determine all the derived products. To the best of recent knowledge, this is the first study that demonstrates the simultaneous identification and quantification of tryptophan and its derivatives employing the useful of ultra-high performance liquid chromatography coupled with photodiode-array and fluorescence detection (UPLC-PDA-FD). Seven compounds of tryptophan and its derivatives were effectively separated within 4 min of chromatographic analysis run time. The method was validated resulting an adequate sensitivity in the range of 0.5–20 μg L-1 (R2=0.991-0.999) with high repeatability (CV <3.9% in average) achieving very low limit of detection and quantification (0.67-2.32 μg L-1 and 2.23-7.73 μg L-1 respectively). The suitability of the method was assessed by application to the extract of ten different rice products that confirmed this rapid method to be suitable for fast determination of tryptophan and related compounds.