Phytochemical characterization, nutritional profile and biological activities of Urtica urens L. plant organs

This study investigates the chemical composition, nutritional profile, and biological activities of aqueous extracts from different organs (leaves, flowers, and stems) of Urtica urens collected in Tunisia. Significant organ-dependent variability was observed in both phytochemical composition and biological activities. Our results revealed that leaves extracts were characterized by the highest Calcium level (23354.44 ppm) and the lowest Na/k ratio. Flowers revealed high amounts of Potassium (16809.11ppm). Nevertheless, high amounts of Sodium (3.62 ppm) were detected in stems extracts. Leaves aqueous extracts showed the highest proportion of total phenols (47.83 mg GAE/g DW), flavonoids (10.30 mg RE/g DW) and flavanols (1.08 mg CE/g DW). However, the highest condensed tannins content was revealed for stems aqueous extracts (7.60 mg CE/g DW). Leaves extracts revealed the strongest biological activities, including higher antioxidant capacity (DPPH and ferric reducing power assays) and the most pronounced antibacterial effects against both Gram-positive and Gram-negative strains. In addition, insecticidal activity against Aphis gossypii varied depending on plant organ, concentration, and exposure time, with leaves generally showing the highest efficacy. UPLC-QTOF/MS analysis of leaf extracts revealed a diverse phenolic profile, including phenolic acids, flavonoids, flavonoid glycosides, and hydrolysable tannin derivatives compounds, which may contribute to the observed biological activities. Overall, these findings highlight the strong influence of plant organ on the chemical and biological properties of U. urens and suggest that leaves represent the most promising fraction for further investigation and potential applications in pharmaceutical, nutraceutical, and agroecological fields.