Antibacterial Activity of an Ethyl Acetate Extract from Cladobotryum virescens Against Plant-Pathogenic Bacteria and Putative Metabolite Annotation by UHPLC-ESI-HRMS/MS

Plant-pathogenic bacteria such as Pseudomonas syringae pv. syringae, P. syringae pv. actinidiae, and Xanthomonas campestris pv. campestris cause major economic losses in fruit and vegetable crops, creating demand for sustainable antibacterial alternatives. In this study, an ethyl acetate extract from Cladobotryum virescens G.R.W. Arnold (C10/110) was evaluated its in vitro antibacterial activity against these three phytopathogens and chemically characterized by UHPLC-ESI-HRMS/MS. Disk diffusion assays revealed clear dose-dependent antibacterial activity, with larger inhibition halos at higher extract concentrations. X. campestris pv. campestris showed the highest sensitivity, exhibiting larger and more uniform inhibition zones and the lowest EC₅₀ value (102 mg mL⁻¹), whereas both Pseudomonas pathovars showed lower susceptibility. Dose–response modeling confirmed a concentration-dependent inhibitory effect, particularly against X. campestris pv. campestris. Metabolomic profiling allowed the identification of 21 secondary metabolites, including phenolic acids, diketopiperazines, flavonoids, fatty acids and several destruxins, most of them reported for the first time in the Cladobotryum genus. These findings highlight C. virescens as a promising source of antibacterial metabolites with potential application in sustainable plant disease management.