Aqueous solutions of organic acids as effective solvents for levodopa extraction from Mucuna pruriens seeds

Levodopa is an amino acid commonly used in the treatment of Parkinson's disease found in several plants, such as Mucuna pruriens. The extraction of levodopa from biomass has been achieved using methanol, ethanol:water mixtures in presence of ascorbic acid, chloroform in alkaline media, and acetonitrile. Aiming at finding more sustainable solvents and develop efficient extraction processes, in this work, aqueous solutions of carboxylic acids (acetic, propionic, citric, glycolic, and lactic acid) and (poly)alcohols (ethanol, ethylene glycol and glycerol) were studied for the extraction of levodopa from Mucuna pruriens seeds. An initial screening with aqueous solutions of these compounds (at 50 wt%) was conducted at 50 degrees C, with an extraction time of 90 min at a solid/ liquid (biomass/solvent) ratio of 1:10. Based on these results, citric acid aqueous solutions were identified as the best solvent, and an experimental design was carried out to optimize the temperature (T), solid/liquid ratio (S:L) and concentration of acid (wt.%), with the following optimal extraction conditions found: T = 60 degrees C, S:L = 1:7 and concentration of acid at 58 wt%. Under these optimal conditions, an extraction efficiency of 9.2 +/- 0.1 wt% of levodopa was achieved. The recovery of levodopa from the acidic aqueous solution was achieved using an ion exchange column, allowing the recovery of approximately 84% of levodopa. The solvent was shown to be reusable in three successive extraction cycles, with no significant losses in the extraction efficiency of levodopa. The results here obtained show that citric acid aqueous solutions can lead to the effective extraction of levodopa from seeds of Mucuna pruriens, serving as basis for the development of more effective and environmentally friendly processes to recover natural products with therapeutic properties.