Analytical methods to monitor dopamine metabolism in plasma: moving forward with improved diagnosis and treatment of neurological disorders

Since dopamine (DA) was discovered as an essential neurotransmitter, with a profound impact on motor control, memory, and behavioral impulses, the pathogenesis of several neurodegenerative and neuropsychiatric disorders have been associated with the dysfunction of the dopaminergic system. Regarding this, the most common drugs used to treat these pathologies act on the dopaminergic neurons. Therefore, the measurement of DA and its precursors and metabolites levels can be a useful tool to help the diagnosis and development of targeted therapeutic approaches to neurological disorders. Furthermore, monitoring and detecting DA metabolism (DA, precursors, and metabolites) in biological samples, like plasma, urine, and cerebrospinal fluid, constitute an interesting subject from a clinical perspective. However, the development of suitable and efficient methods to determine these compounds in biological samples remains a challenge. Thus, this review provides an overview of the recent advances and available methodologies to quantify DA and its precursors and metabolites in plasma samples focusing on previous reports which used less than two milliliters. Also, it deals with the actual extraction and separation techniques, as well as detection modes; and it gives a perspective, on the present-day, about the use of analytical methods as a helpful tool to improve diagnosis.