Quality assessment of "naturally occurring" high-percentage L-dopa commercial products proposed as dietary supplements on the Internet: from labeling to analytical findings.

Introduction: Levodopa (L-dihydroxyphenylalanine or L-dopa) is a precursor of the neurotransmitter dopamine and is used in Parkinson's disease therapy. L-dopa dietary supplements are widely marketed as brain support. Among the L-dopa products claiming to contain botanical extracts, those from Methods: Four L-dopa products marketed as dietary supplements were purchased online and analyzed for labeling accuracy. The identification of L-dopa and the detection of undeclared pharmaceutical or nootropic ingredients were carried out via mass spectrometry (LC-MS Q-TOF). Nuclear magnetic resonance (NMR) spectroscopy was used to confirm the presence of L-dopa and quantify it. Furthermore, a Google Trends analysis was conducted to study interest in the terms "levodopa" and "brain supplements" and their Italian equivalents, over the last 10 years in Italy and globally. Results: Visual inspection of labeling revealed that the extract of Discussion: The obtained results showed evidence of potential risks related to consuming dietary supplements purchased online containing high-dose L-dopa. These risks arise from the inclusion of unauthorized botanical extracts, unclear labeling, and inconsistencies between labeled and actual dosages. Given the observed increasing public interest in levodopa, these findings highlight the need to control this market and inform consumers and physicians about the risks of purchasing unauthorized online products.