Ceylon cinnamon (Cinnamomum verum J. Presl) bark essential oil (CBO) represents a promising source of natural bioactive compounds for biological plant protection. For the first time, the antibacterial and antifungal activity of CBO was systematically evaluated against a curated panel of phytopathogenic strains (IOR collection), revealing broad-spectrum efficacy across both bacteria and filamentous pathogens. This study evaluated its chemical composition, antimicrobial activity against phytopathogens, effects on bacterial metabolic activity, and its ability to induce plant defence responses. CBO was dominated by cinnamaldehyde, linalool, and eucalyptol. The oil exhibited strong antibacterial activity against Dickeya dadantii, Pectobacterium carotovorum, Pseudomonas syringae, and Xanthomonas hortorum as well as antifungal activity against Fusarium graminearum, F. culmorum, Rhizoctonia solani and Phytophthora cinnamomi. Metabolic assays revealed a marked reduction in bacterial metabolic activity, indicating that CBO disrupts physiological processes and inhibits growth. In planta experiments showed that foliar application of CBO stimulated PAL activity in wheat leaves without visible phytotoxic symptoms. These findings demonstrate a multifunctional mode of action of CBO, combining direct antimicrobial effects with the elicitation of plant defence responses, and support its potential application in sustainable crop protection.

Solidago gigantea Aiton is an invasive plant species rich in bioactive secondary metabolites. The aim of this study was to characterize the phytochemical profile of an ethanolic S. gigantea extract and to evaluate its antibacterial and chemoprotective potential using in vitro models. Chemical analysis revealed a high content of phenolic compounds, dominated by chlorogenic acid, along with other phenolic acids and flavonoids, including rutin and quercitrin. The extract also contained saponins and a diverse lipophilic fraction composed of long-chain hydrocarbons, alcohols, fatty acids, phytosterols, and triterpenoids. The extract exhibited strong antibacterial activity against Gram-positive bacteria, including methicillin-resistant Staphylococcus strains, while Gram-negative bacteria and yeasts were less susceptible. In cancer cell models, the extract showed selective antiproliferative and cytotoxic effects, particularly in colorectal and breast cancer cell lines, including doxorubicin-resistant phenotypes, with minimal effects on normal fibroblasts. The extract also showed antioxidant and cytoprotective properties, reflected by a reduction in intracellular reactive oxygen species under both basal and oxidative stress conditions. Increased accumulation of rhodamine 123 in resistant cancer cells suggested a potential inhibition of P-glycoprotein-mediated efflux. Overall, the results indicate that S. gigantea extract exhibits multi-target biological activity associated with its polyphenolic composition, supporting its potential application in chemoprevention, adjuvant cancer therapy, and the control of Gram-positive bacterial infections.