An Overview of Methods for L-Dopa Extraction and Analytical Determination in Plant Matrices

Abstract

L-dopa is a precursor of dopamine used as the most effective symptomatic drug treatment for Parkinson's disease. Most of the L-dopa isolated is either synthesized chemically or from natural sources, but only some plants belonging to the Fabaceae family contain significant amounts of L-dopa. Due to its low stability, the unambiguous determination of L-dopa in plant matrices requires appropriate technologies. Several analytical methods have been developed for the determination of L-dopa in different plants. The most used for quantification of L-dopa are mainly based on capillary electrophoresis or chromatographic methods, i.e., high-performance liquid chromatography (HPLC), coupled to ultraviolet-visible or mass spectrometric detection. HPLC is most often used. This paper aims to give information on the latest developments in the chemical study of L-dopa, emphasizing the extraction, separation and characterization of this compound by chromatographic, electrochemical and spectral techniques. This study can help select the best possible strategy for determining L-dopa in plant matrices using advanced analytical methods.

Development and Validation of a Reversed-Phase HPLC Method with UV Detection for the Determination of L-Dopa in Vicia faba L. Broad Beans

“…The presence of the catechol moiety in the chemical structure characterizes LD as a chromophore with a λ max value of 280 nm and allows us to obtain UV detection results sufficiently sensitive for LD determination in vegetable matrices [ 10 ]. Since the absorption spectrum of LD is highly characteristic ( Figure 1 B), its determination by spectrum acquisition (LC-UV analysis) is also selective.…”

“…Since the absorption spectrum of LD is highly characteristic ( Figure 1 B), its determination by spectrum acquisition (LC-UV analysis) is also selective. Although several scientific works reported the separation and quantification of LD in Vicia faba L. by using liquid chromatography coupled to a UV–Vis detector (LC/UV–Vis) [ 8 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 ], there are still some limitations regarding LD extraction/stability, chromatographic conditions, and method validation.…”

“…LD instability will also influence the choice of the extraction technique. Typical extraction techniques include liquid–solid extraction, Soxhlet extraction, microwave-assisted extraction, and ultrasound-assisted extraction [ 10 ]. However, the latter two techniques, although significantly improving the extraction procedure in terms of automation and solvent consumption, are less used because thermal effects can reduce the final concentration of L-Dopa [ 11 ].…”

“…Secondly, low-molecular-weight polar compounds, such as LD, are generally difficult to separate by using reversed-phase liquid chromatography (RP-LC) [ 10 ]. Generally, it is required to work below the pKa of the compound where it will be completely protonated, or to use an ion pair reagent to increase retention time.…”

“…Chromatographic conditions as regards LC column and mobile-phase composition are also fundamental to obtain reliable results. Mostly, C 18 stationary phases have been used due to the highly polar structure of the analyte [ 10 , 11 , 13 , 23 ]. Acetate/phosphate buffers at acidic pH values (<3) have also been used, although some papers report the use of acetate/phosphate buffers at pH of 4.00, 4.55, 4.66, or 7.00 [ 10 , 19 , 20 , 23 , 24 , 37 ].…”