A systematic study of the high-pressure effect on the pyrolysis of solid a-amino acids L-leucine (C6H13NO2), L-alanine (C3H7NO2), L-aspartic acid (C4H7NO4) and glycine (C2H5NO2) is presented. The experiments were performed at 7.7 GPa during 1 min in the temperature range from 300 to 800 degrees C. The effect of the pyrolysis under high pressure on the electronic structure of carbon and nitrogen was investigated by X-ray photoelectron spectroscopy (XPS). The effect on the atomic bonding configuration was studied by infrared and Raman spectroscopy. The obtained results suggested that the thermal decomposition of amino acids under pressure at 300 and 400 degrees C started with dehydration followed by polymerization. For temperatures above 600 degrees C it was observed the formation of graphite-like structures functionalized with nitrogen and oxygen atoms. (C) 2018 Elsevier B.V. All rights reserved.