Screening phytochimique et l’évaluation de quelques activités biologiques des extraits d’Ortie (Urtica dioïca), collectée de la région de Mostaganem, en vue de valorisations cosmétiques.

Abstract

Nettle is a commonly widespread plant. Everyone knows it for its stinging contact. In fact, it is a medicinal plant used since antiquity for its numerous therapeutic properties. In order to understand the biological activities of medicinal plants traditionally used by the population, our work focused on the study of methanolic extracts of Urtica dioica L. leaves using the Soxhlet method and methanolic maceration. Phytochemical screening highlighted a richness of bioactive substances. The characterization of alkaloids and flavonoids on TLC plates "Thin-Layer Chromatography" revealed a significant number of spots, indicating a substantial abundance of these secondary metabolites. We attempted to analyze these extracts, which revealed the richness of extracts MET-01 and MET-02 in phenolic compounds, confirming the results of polyphenol quantification by the Folin-Ciocalteu method, where the contents are respectively: 107.07 and 44.86 mg GAE/g and in flavonoids with contents of 12.28 and 8.51 mg/g. Similarly, DPPH radical scavenging showed that the methanolic extracts of Urtica dioica possess significant antioxidant activity (IC50 = 43.78 mg/ml for extract MET-02 and IC50 = 45.76 mg/ml). Extraction by maceration proved more advantageous in terms of antioxidant activity measured by the DPPH test. The antimicrobial effect was determined by the disk diffusion method with different concentrations of the extracts on five Gram-negative and Gram-positive strains (Escherichia coli, Staphylococcus aureus, Klebsiella pneumoniae, Bacillus cereus, and Pseudomonas aeruginosa). Both methanolic extracts by maceration and Soxhlet showed moderate activity against all tested microorganisms, particularly: Escherichia coli, Staphylococcus aureus, Klebsiella pneumoniae, Bacillus cereus, and Pseudomonas aeruginosa. The evaluation of anti-inflammatory activity in vitro by the albumin thermal denaturation inhibition method and the red blood cell membrane protection test against osmotic and thermal stress showed that the methanolic extract of Urtica dioica has an excellent ability to protect BSA from thermal denaturation. Similarly, the analysis of red blood cell membrane protection against osmotic and thermal stress showed that the efficacy of the methanolic extract by maceration MET-02 of Urtica dioica is superior to that of the Soxhlet extract MET-01. The results of this work allowed us to affirm that this plant exhibits very good antioxidant, anti-inflammatory, and antibacterial properties that can be used in various fields, particularly therapeutic and nutritional. However, further studies are needed to identify the biologically active molecules to specify the molecular mechanisms responsible for these effects.