Comparative Elicitation of Artemisinin in Artemisia annua L.: ZnO Nanoparticles Surpass Salicylic Acid via Antioxidant and Gene Activation Pathways

This study investigated the effects of zinc oxide nanoparticles (ZnO-NPs) and salicylic acid (SA) on artemisinin production in Artemisia annua L., the compound with bioactivity against various diseases, including malaria. A range of methods have been suggested to increase artemisinin production. This research focused on enhancing artemisinin content through elicitor application. Six- week-old plants were subjected to foliar spray at different dose of nanoparticles and SA over a 96 h period. Results demonstrated that ZnO-NPs act as a stronger elicitor compared to SA; specifically, expose to 200 mg L–1 ZnO-NPs for 96 h significantly increased the artemisinin content by 43.3% relative to the control. Gene expression analysis revealed significant upregulation of AaWRKY1, AaMYB2, HMGR, and CYP71AV1 in response to ZnO-NPs, mediated likely through H2O2 signalling. Concurrently, ZnO-NPs enhanced total protein content and induced antioxidant and defence-related enzymes including SOD, CAT, POX, and PAL. In contrast, 1 mM SA modestly upregulated AaWRKY1, AaMYB2, and HMGR, but had negligible impact on CYP71AV1. This is the first report demonstrating that ZnO-NPs, as effective elicitor, do not induce oxidative damage, but instead stimulated a protective antioxidant response that facilitate redirection of metabolic flux toward enhancing the yield of pharmaceutically important secondary metabolite such as artemisinin.