Free amino acids like gamma-aminobutyrate (GABA) are known for their biological roles in human body. In CNS, GABA plays as an inhibitory neurotransmitter, and in peripheral tissues, GABA exhibits an ability to lower blood pressure. Those food products containing GABA as active ingredients are named “Kenko Shokuhin” direct translated as “health food”. Since most free amino acids are supplied via food intake, it is important to know the quantity of free amino acids in food supplies. Unfortunately, the information of free amino acids in foods is limited due to the lack of database(s). We have carried out the experiments to quantitate the free amino acids in foods by using UHPLC to establish database for free amino acids in food.
   Free amino acids were extracted from homogenized food samples. For the extraction, various extraction solvents, such as buffer only, or in addition of various detergents or organic solvent, were examined for the efficiency and for the ability to avoid protein contamination. Extracted amino acids were derivatized with 4-fluoro-7-nitrobenzofurazan and analyzed on a Hitachi UHPLC equipped with Agilent ODS column and UV-VIS detector. The system operated with an injection volume of 10 microliter, detection limit about 0.8 pmol level, and analytical time of 8 min.
   Our best extraction method was the use of buffer alone based upon the efficiency and ability to avoid protein contamination. Almost all of the food extracts exhibit to contain most of the amino acids including GABA. We present amino acid distribution for nearly 150 kinds of vegetables and fruits. We also present chromatographic quality of our analysis, i.e., reproducibility.