Hydroponic modulation of Sonchus oleraceus L. leaf composition: impact of NPK balance on nutritious attributes and...

Sonchus oleraceus L. (common sowthistle) is a wild leafy vegetable with recognized culinary and pharmacological potential. In hydroponics, controlled nitrogen (N), phosphorus (P), and potassium (K) imbalances act as an agronomic eustress (positive stress) that stimulates the defensive accumulation of secondary metabolites, thereby enhancing the leaves' biological value. Aiming to exploit this modulation, we evaluated the impact of varying concentrations of N (100-200 mg L^-1), P (47-105 mg L^-1), and K (250-525 mg L^-1) on hydroponic cultivation of Sonchus oleraceus leaves, based on previous optimized research on agronomic performance. The leaves in this study were analysed for proximate composition, free sugars, organic acids, fatty acids, tocopherols, and phenolic compounds, as well as their antioxidant and antimicrobial capacities.

Results indicated that the proximate composition was not substantially affected by nutrient modulation; however, significant differences were observed in individual phytochemical constituents, particularly in tocopherol and phenolic compound levels. Antioxidant assays (thiobarbituric acid reactive substances (TBARS) and oxidative haemolysis inhibition assay (OxHLIA)) showed that nutrient supply influenced lipid peroxidation inhibition, demonstrating greater potential when compared to the Trolox standard, while in oxidative haemolysis, the half-maximal inhibitory concentration (IC₅₀) values of Sonchus oleraceus leaves were comparable to those of the same control. Antimicrobial tests demonstrated moderate inhibitory activity against foodborne pathogens.

Nutrient solutions enriched with different proportions of NPK produced Sonchus oleraceus leaves with antioxidant potential in the lipid peroxidation pathway. Overall, these findings highlight that NPK management in hydroponic cultivation can modulate the phytochemical profile and biological potential of Sonchus oleraceus leaves, reinforcing their nutritional and functional value. © 2026 Society of Chemical Industry.