Background: This study investigated the phenolic profile, antioxidant capacity, antibacterial effect, and antihemolytic activity of nettle leaves from two understudied Algerian species, Urtica pilulifera and Urtica urens.
Methods: Urtica pilulifera and Urtica urens leaves extracts were prepared by maceration using methanol and distilled water respectively. Their phytochemical analysis (total phenolic content, flavonoids, hydrolysable and condensed tannins) was determined. The chemical profle of these extracts was performed using ultra-high-performance liquid chromatography diode array detection tandem mass spectrometry. Antioxidant activity (using the 2,2-diphenyl-1-picrylhydrazyl free radical scavenging method), antibacterial activity (using disk diffusion method), and antihemolytic activity were carried out.
Results: Results reveal high levels of flavonoids, tannins, alkaloids, and terpenoids. Several classes of compounds were identified in the extracts. Phenolic acid and other acids and their derivatives and flavonoids were detected in the extracts, with 4-O-caffeoyl-quinic acid and 5-O-caffeoyl-quinic acid being the main constituents in both extracts. Caffeic acid was also the main constituent present only in U. urens extract. For antioxidant activity of the methanolic extract of U. pilulifera and the aqueous extract of U. urens, the percentage inhibition value (82.76% and 59.06%) and the half-maximum inhibitory concentration (IC50) value (302 and 423 μg/mL), respectively, were obtained. Antibacterial activity of nettle extracts (10 mg/mL) demonstrated the sensitivity of pathogenic strain susceptibility. The strongest antibacterial effect on tested strains was found in the aqueous extract of U. urens against Staphylococcus aureus (21 ± 0.41 mm) compared to the methanolic extract of U. pilulifera (16 ± 0.40 mm). The antihemolytic activity in the methanolic and aqueous extracts was 76.26% and 60.67%, respectively. The methanolic extract exhibited exceptional antihemolytic effect, with an IC50 value of 327 μg/mL, whereas the aqueous extract had an IC50 value of 412 μg/mL.
Conclusions: The study confirms the presence of bioactive substances in the nettle species, including flavonoids and tannins, which possess antioxidant, antibacterial, and antihemolytic properties, and can be processed into food and pharmaceutical products.