Etude phytochimique, activité anti-oxydante et antibacterienne des huiles essentielles de deux plantes médicinales : in vitro et in silico

Abstract

Nepeta nepetella subsp. Amethystina (Poir.) Briq and Satureja candidissima Munby Brik are medicinal and aromatic plants belonging to the Lamiaceae family, traditionally used in Algerian medicine. This study aims to analyze the phytochemical composition, evaluate the antioxidant and antibacterial activities, and predict the mechanism of action of the essential oils extracted from the aerial parts of N. nepetella and S. candidissima, collected from the regions of Naâma and Ain Temouchent, respectively. Qualitative analysis using GC-MS of the obtained essential oils revealed chemical variability, with 57 compounds identified in N. nepetella essential oil and 54 in S. candidissima essential oil, representing 90.98% and 91.01% of the total composition, respectively. The major components of N. nepetella essential oil are 4aα,7α,7aβ-Nepetalactone (58.98%), 4aα,7α,7aα-Nepetalactone (10.23%), Spiro(5.6)dodecane (5.45%), and Camphor (4.98%). For S. candidissima, the major components include Pulegone (53.26%), (+)-Menthone (11.02%), Borneol (4.43%), 2-Cyclohexen-1-one, 3-methyl-6-(1-methylethylidene) (2.50%), and 3- Octanol (2.09%). Biologically, DPPH and FRAP tests demonstrated that Nepeta nepetella essential oil exhibits stronger antioxidant activity than Satureja candidissima. However, for total antioxidant capacity (CAT), Satureja candidissima showed greater effectiveness. Additionally, Satureja candidissima exhibited higher antibacterial activity against Escherichia coli, Bacillus cereus, Staphylococcus aureus, and Pseudomonas aeruginosa, whereas Nepeta nepetella was more effective against Bacillus licheniformis and Listeria monocytogenes. In silico molecular docking and ADMET studies were conducted to elucidate the underlying antibacterial mechanism and antioxidant potential. The recorded data indicated that the antibacterial activity of the essential oil compounds could be attributed to the inhibition of enoyl-[acyl-carrier-protein] reductase FabI [NADPH] (PDB ID: 4ALL). The most active compounds were minor components. Docking results also suggested that the essential oil components could exert their antioxidant activity in vitro by inhibiting xanthine oxidase (PDB ID: 3NRZ). Therefore, N. nepetella and S. candidissima could serve as novel natural sources of antioxidants and antiseptics, with potential applications in the food and pharmaceutical industries as alternatives to synthetic additives.