Influence of silver nanoparticles on the in vitro growth, phenolic profile, antioxidant potential, enzyme inhibition, and essential oil composition of Clinopodium nepeta subsp. spruneri (Boiss.) Bartolucci & F. Conti

Silver nanoparticles (AgNPs) are increasingly recognized as active elicitors capable of modulating plant growth and metabolism. This study evaluated the effects of AgNPs (1.0-50.0 mg/L) on in vitro shoot cultures of Clinopodium nepeta subsp. spruneri (Boiss.) Bartolucci & F. Conti (Lamiaceae). AgNP exposure significantly reduced shoot length, leaf and node numbers, and completely suppressed root formation, while biomass accumulation increased in a concentration-dependent manner. High-performance liquid chromatography (HPLC) identified rosmarinic acid (RA) as the major phenolic, with levels rising 2.5- to 4.5-fold in treated shoots compared with control and wild plants. The maximum RA content, total phenolic concentration, antioxidant activity (DPPH and FRAP), and acetylcholinesterase (AChE) inhibition were observed at 20.0 mg/L AgNP. In contrast, the highest flavonoid content was recorded in the wild plant. Gas chromatography-mass spectrometry (GC-MS) analysis revealed that isoeugenol dominated in AgNP-treated cultures, while menthalactone was the principal constituent in both control and wild samples. These findings demonstrate that AgNPs substantially alter the metabolic profile of C. nepeta subsp. spruneri, highlighting their potential as elicitors for enhancing phenolic accumulation, antioxidant activity, and enzyme inhibition under in vitro conditions.