Enhanced Extraction of Levodopa from Mucuna pruriens Seeds Using Aqueous Solutions of Eutectic Solvents

Levodopa (L-dopa) is an amino acid precursor of catecholamines dopamine, norepinephrine, and epinephrine, which can be used in the treatment of Parkinson's disease. Levodopa is present in several vegetable sources, such as Mucuna pruriens seeds. However, the extraction of levodopa from vegetable matrices is usually carried out with volatile organic solvents (methanol, hexane, and chloroform). In this work, we demonstrate that aqueous solutions of eutectic solvents (ES) can be used as alternative solvents for the extraction of levodopa. ES based on carboxylic acids or polyols combined with cholinium chloride ([Ch]Cl) were studied. Experimental conditions such as the temperature, solid-liquid (solvent/biomass) ratio, and ES concentration in aqueous solutions were optimized by a response surface methodology, with the aim of maximizing the levodopa extraction yield. Extraction yields of up to 9.9 +/- 1.0 wt % (levodopa per dry weight of M. pruriens seeds) were obtained at a temperature of 56 degrees C, a solid-liquid ratio of 1:7, and an ES concentration close to 35 wt %. The recovery of levodopa from the ES aqueous solutions was achieved by a subsequent solid-phase extraction step, allowing the recovery of 87% of the extracted levodopa with high purity. This step further allowed solvent recovery and reuse, demonstrating that the solvent can be reused at least three times without compromising the extraction yield of levodopa. This work shows the remarkable capacity of ES aqueous solutions to extract the value-added compound levodopa from biomass and the possibility of applying reusable solvents, paving the way for their use as alternative solvents to extract bioactive compounds from natural sources.