Comprehensive Assessment of Morphological, Biochemical and Molecular Responses of Melissa officinalis subsp. officinalis L. Grown in Vitro Conditions to Copper Oxide Nanoparticles

OpenAlex · English

This study explores the in vitro effects of copper oxide nanoparticles (CuO-NPs) on Melissa officinalis L. subsp. officinalis (lemon balm) by evaluating morphological, biochemical, and molecular responses. Seedlings were treated with CuO-NPs at 0.1, 1.0, and 10.0 mg/L to assess growth parameters, secondary metabolite production, antioxidant activity, enzyme inhibition, essential oil composition, and gene expression of PAL, TAT, and RAS. Low CuO-NP concentration (0.1 mg/L) significantly enhanced shoot elongation, while 10.0 mg/L induced strong root proliferation but inhibited shoot growth. Total phenolic (TPC) and flavonoid (TFC) contents peaked at 10.0 mg/L, correlating with increased antioxidant activity in CUPRAC, DPPH, and ABTS assays. HPLC analysis revealed elevated rosmarinic acid and reduced caffeic and p-coumaric acid levels, suggesting pathway redirection. Enzyme inhibition assays showed that 1.0 mg/L yielded the strongest AChE inhibition, while higher doses improved inhibition of MAO, urease, and HIV-1 RT. GC-MS analysis indicated altered essential oil profiles under CuO-NP exposure, including increased geranial and neral levels. qRT-PCR confirmed dose-dependent upregulation of PAL, TAT, and RAS genes, particularly at 10.0 mg/L, supporting enhanced phenylpropanoid biosynthesis. Collectively, CuO-NPs act as abiotic elicitors in a concentration-dependent manner, promoting bioactive compound production and antioxidant potential. These findings highlight the potential of CuO-NPs in improving the phytochemical quality of Melissa officinalis under controlled conditions.