Copper oxide nanoparticles modulate biomass, secondary metabolite accumulation, and antioxidant defense in adventitious root cultures of Talinum paniculatum

Copper oxide nanoparticles (CuO-NPs) have gained increasing attention as abiotic elicitors due to their ability to influence plant metabolic activity through redox-related mechanisms. This study investigated the dose-dependent effects of CuO-NPs on biomass, secondary metabolite accumulation, oxidative stress markers, antioxidant capacity, and antioxidant enzyme activities in adventitious root cultures of Talinum paniculatum. Adventitious roots were exposed to CuO-NPs at concentrations of 0, 50, 100, and 150 mg L⁻¹ for two weeks under in vitro conditions. Biomass was assessed based on fresh and dry weights, while saponin and stigmasterol contents were quantified using high-performance liquid chromatography. Oxidative responses were evaluated by determining malondialdehyde and hydrogen peroxide levels, antioxidant capacity by DPPH radical scavenging activity, and enzymatic antioxidant responses by superoxide dismutase, catalase, and ascorbate peroxidase activities. Moderate CuO-NPs concentrations (50–100 mg L⁻¹) significantly enhanced secondary metabolite accumulation, antioxidant capacity, and antioxidant enzyme activities, accompanied by controlled increases in oxidative stress indicators. In contrast, exposure to 150 mg L⁻¹ CuO-NPs reduced biomass and antioxidant responses, indicating oxidative stress–induced metabolic inhibition. These findings demonstrate that CuO-NPs act as effective elicitors at appropriate concentrations and highlight their potential application for improving secondary metabolite production in T. paniculatum adventitious root cultures.