Ion-Pair LC Analysis of Pyrroloquinoline Quinone in Neurotransmitter Amino Acid Incubations: Determination of Chemical Kinetics

Neurotransmitters are the chemical messengers of the brain. Many neurodegenerative diseases of the central nervous system are related to abnormal neurotransmitter activity. Pyrroloquinoline quinine (PQQ) has previously been shown to be a promising candidate for preventing cognitive deficit in neurodegeneration. To investigate whether PQQ can modulate the levels of brain neurotransmitter amino acids, a rapid and reliable ion-pair liquid chromatographic method was established and validated for the analysis of PQQ in reaction mixtures containing specific neurotransmitter amino acids. The reaction mixtures were separated on an amethyst C18-P reverse-phase column with 35:65 (v/v) acetonitrile:20 mM potassium dihydrogen phosphate, pH 5.5, containing 20 mM tetrabutyl ammonium bromide as mobile phase at a flow rate of 0.8 mL min−1. The validated method was applied successfully to study the chemical kinetics of PQQ reactions with five neurotransmitter amino acids. Order of reaction n, rate constant k, and activation energy E a values for the reactions were calculated. This work provides important information for studying the possible protective mechanisms of PQQ in neurodegenerative diseases. Furthermore, the simplicity of this method combined with its sensitivity and reliability make it a novel contribution in the field of neurotransmitter research.