Green-synthesized lanthanum nanostructures modulate redox balance and phytochemical responses in lead-stressed Zataria multiflora

Lead (Pb) toxicity disrupts redox homeostasis and impairs phytochemical stability in medicinal plants; however, nanomaterial-based approaches to alleviate oxidative stress in Pb-stress conditions have not been extensively researched yet. In the present research, lanthanum-based nanostructures (La NCs) were prepared via eco-friendly method employing Arabic gum and spermine as well as were explored for their efficacy in ameliorating Pb-stress-induced oxidative damage in Zataria multiflora . The plants were subjected to different levels of Pb contamination, such as 0, 250, 500, and 750 mg/kg and then treated with La NCs in doses ranging from 0 to 200 ppm. The effect of Pb toxicity (750 mg/kg) led to an increase in indicators of oxidative stress, including H₂O₂ and MDA, along with a significant decrease in the activity of phytochemicals and antioxidant response. Treatment with La NCs significantly improved these effects dose-dependently, showing the optimal dose at 100 ppm. At 100 ppm of La NCs treatment, oxidative damage was decreased by 40–60%, whereas antioxidant responses were stimulated by 35–70%. Simultaneously, metabolic stability was enhanced through the recovery of essential oils and related phytochemical characteristics. Particularly, La NCs stabilized with Arabic gum consistently showed greater activity than those stabilized with spermine, suggesting a stabilization-mediated influence on redox reactions and plant-NCs interactions. This study demonstrates that green-synthesized La NCs have potential applications as modulators of oxidative stress and antioxidants within the plant system under Pb stress.