Evaluation of Anti‐ <i>Xanthomonas axonopodis</i> pv. <i>citri</i> Activity of <i>p</i> ‐Hydroxybenzaldehyde‐Borneol Hybrid Derivatives and a Preliminary Study of the Mechanism

ABSTRACT In this study, the antibacterial activity of a series of p ‐hydroxybenzaldehyde derivatives containing borneol was evaluated. Among the tested compounds, B8 exhibited the most potent inhibitory effect against Xanthomonas axonopodis pv. citri ( Xac ), with a median effective concentration EC 50 ) of 40.1 µg/mL, which was lower than that of the control agent thiadiazole copper (TC; EC 50 = 61.9 µg/mL). The antibacterial activity of B8 was further confirmed by scanning electron microscopy (SEM) and bacterial growth curve analyses, both of which indicated substantial suppression of Xac growth. Preliminary mechanism studies suggested that B8 could inhibit the production of extracellular polysaccharides and extracellular enzymes in Xac , providing initial insight into its mode of action. In addition, molecular docking and density functional theory (DFT) calculations revealed a stronger binding affinity of B8 toward succinate dehydrogenase (SDH) compared to TC.