Mediterranean Aromatic Plants and Eco-friendly Techniques for Agricultural Weed Management: Exploration of the Diversity of Secondary Metabolites of Algerian and Italian Thymus Species.

English

Weed control poses a significant challenge to agriculture, warranting the development of effective but environmentally safe herbicides. In this sense, this research study focused on the evaluation of the phytotoxic activity of four essential oils (EOs) from Mediterranean species of Thymus sp. pl. to identify new biomolecules with herbicide potential and the formulation of a prototype of a nanoherbicide for a sustainable weed control. The chemical characterization of EOs was performed by GC-MS. Biological assays were conducted to assess the herbicidal effect of the EOs on pre and post-emergence of two weed species under in vitro and in vivo conditions. In vitro experiments were performed to screen the phytotoxicity of the EOs. Then, the effectiveness of the most performing EOs was evaluated under in vivo conditions. Once this effectiveness demonstrated, a prototype of a nanoherbicide was formulated. EOs were encapsulated in SiNPs. The efficacies of these preparations were compared to that of pristine EOs. Phytochemical analysis revealed a great diversity of compounds. All the EOs expressed a potent herbicidal activity against the tested species under in vitro conditions. Total inhibition of seed germination and seedling growth were recorded. These results were confirmed under greenhouse experiments. Concerning the fabricated nanoherbicide, the loading efficiencies of the EOs in SiNPs were from 26 to 64%. Transmission electron microscopy (TEM) revealed spherical and regular SiNPs with a size range of 220–300 nm. Fourier transform infrared (FT-IR) spectroscopy confirmed EO loading by the presence of characteristic peaks of isoprenoids and isomeric compounds. Herbicidal bioassays with pristine thyme EO in post-emergence treatments on weed species seedlings exhibited a significant concentration-dependent herbicidal activity. Encapsulation with SiNPs further enhanced the herbicidal efficacy of the EOs in comparison to the pristine EO. EO-SiNPs induced significant ROS production, leading to cell membrane damage and an imbalanced antioxidant system. These results suggest significant potential for developing an effective nanobioherbicide using thyme EO encapsulated in SiNPs.