Mycorrhizal Fungal Inoculation Reshapes Chemotype, Nutritional Status, and Metabolic Signatures to Enhance Bioactivity in Origanum compactum Benth.

Arbuscular mycorrhizal fungi (AMF) establish a reciprocal interaction with plant roots, enhancing nutrient acquisition, stress tolerance, and the production of bioactive metabolites. These symbiotic fungi represent a sustainable alternative to chemical fertilizers to improve the quality and yield of medicinal and aromatic plants such as Oregano (Origanum compactum). In this study, we investigated the effects of mycorrhizal inoculation on the chemical composition, nutritional profile, and biological activities of Oregano cultivated under greenhouse conditions. Compared with non-mycorrhizal plants, mycorrhizal-inoculated plants showed approximately 33% higher protein content and 28% higher total sugar content, while lipid concentration decreased slightly by about 7%. Mycorrhizal inoculation also promoted the accumulation of secondary metabolites, resulting in increased concentrations of total polyphenol and flavonoid contents by approximately 33% and 25%, respectively. These compositional changes were associated with markedly enhanced antioxidant capacity, exceeding that of the reference antioxidant, as well as improved antibacterial activity, characterized by larger inhibition zones and lower minimum inhibitory concentrations against tested pathogens. Overall, mycorrhizal fungal inoculation reshaped the chemical composition and the major bioactive compounds of Oregano, thereby enhancing its nutritional and antimicrobial potential. These findings highlight the potential of AMF-based cultivation strategies to improve the phytochemical quality and medicinal potential of Oregano while supporting sustainable agricultural production.