Enhancing Salt Tolerance and Bioactivity in Achillea fragrantissima through ZnO Nanoparticles: Growth, Antimicrobial, and Hepatoprotective Benefits.

Achillea fragrantissima, an aromatic perennial herb extensively used in traditional Middle Eastern medicine, possesses remarkable therapeutic properties. This study aimed to evaluate the effects of zinc oxide nanoparticles (ZnO-NPs) on the growth, phytochemical profile, antimicrobial activity, and hepatoprotective potential of A. fragrantissima, which grows under saline stress in an in vitro culture system. Seeds were cultured on half-strength MS medium and exposed to varying salinity levels (0, 2000, and 3000 ppm) and ZnO-NP concentrations (0, 2.5, 5, and 10 mg/L) using a split-plot design. Germination, shoot, and root induction were studied under these conditions. Methanolic leaf extracts were analyzed via GC-MS to identify bioactive compounds, while ISSR-PCR was employed to assess genetic stability. Antibacterial activity was tested against Escherichia coli, methicillin-resistant Staphylococcus aureus (MRSA), and Pseudomonas aeruginosa. Furthermore, hepatoprotective effects were evaluated in BALB/c mice using an acetaminophen-induced liver injury model. Results revealed that moderate salinity (2000 ppm) enhanced growth, whereas higher salinity (3000 ppm) inhibited development. Low concentrations of ZnO-NPs mitigated salt stress and further promoted growth. ZnO-NP treatments also enhanced phytochemical accumulation, which correlated with stronger antibacterial activity. Notably, methanolic extracts provided significant hepatoprotection, evidenced by reduced serum liver enzymes and improved antioxidant parameters. These findings underscore ZnO-NPs as a promising approach to enhance growth, stress tolerance, bioactive compound production, and therapeutic potential of A. fragrantissima under saline conditions.