Accumulation of l-DOPA in various organs of faba bean and influence of drought, nitrogen stress, and processing methods on l-DOPA yield

Faba bean ( Vicia faba L.) has been identified as a rich source of l -DOPA, which is used in treating Parkinson's disease. Biosynthesis and accumulation of active substances such as l -DOPA in plant tissues may interact with growing conditions and processing methods. Accumulation trends of l -DOPA in various faba bean organs and the effect of drought stress and N fertilization on l -DOPA content were studied in a field and two greenhouse experiments. The influence of various processing methods on l -DOPA content of faba bean tissues was evaluated. The highest l -DOPA content was detected in fresh leaves (22.4 mg g −1 ) followed by flowers, young pods, mature seeds, and roots. Regardless of processing method, l -DOPA concentration in faba bean tissues was significantly reduced when tissues were boiled or dried. Among various methods of processing, freezing had the lowest detrimental effect, reducing l -DOPA concentrations by 24.1% and 21.1% in leaves and seeds, respectively. Drought stress elevated l -DOPA concentration, and maximum l -DOPA (23.3 mg g −1 of biomass) was extracted from plants grown under severe drought stress. However, l -DOPA yield ( l -DOPA concentration × biomass) was compromised, owing to the adverse influence of drought stress on dry matter production. No significant difference in l -DOPA concentration was detected among various N application rates.