Effects of water limitation on the production of key secondary metabolites with medicinal properties in Plantago lanceolata and Tanacetum parthenium

Plant secondary metabolites play vital roles in growth, defence, and human pharmacological applications, with medicinal plants historically used to treat diseases. However, climate-change-induced drought may threaten medicinal plant growth and metabolite production. This study examines drought effects on two medicinal plants common in the UK: <em>Plantago lanceolata</em> and <em>Tanacetum parthenium</em>. Under glasshouse conditions, we compared growth, chlorophyll content, and photosystem II efficiency (Fv/Fm) in well-watered vs. low-watered plants. High-performance liquid chromatography (HPLC) measured the concentration of parthenolide in <em>T. parthenium</em> and verbascoside in <em>P. lanceolata</em> leaves, with both compounds<br> unaffected. Parthenolide content in <em>T. parthenium</em> decreased with low water, while verbascoside in <em>P. lanceolata</em> showed no significant change. This study highlights drought’s impact on medicinal plant growth and metabolite production, emphasizing the need for further research on environmental factors affecting secondary metabolites under climate change.