Bioactive compounds from plant sources: profiling and anti-blight efficacy against phytopathogens

Bacterial leaf blight (BLB) is a major threat to global rice production, leading to yield losses of up to 40% despite extensive disease management practices. The persistence of Xanthomonas oryzae pv. oryzae (Xoo) necessitates an eco-friendly and effective alternative to synthetic pesticides. This study investigates the bio-control potential of various extracts and essential oils (EO) extracted via hydro-distillation from different plant sources (Ocimum tenuiflorum , Azadirachta indica , Mentha spicata , Trachyspermum ammi, and Garcinia mangostana). Among the tested samples, Trachyspermum ammi seed EO (TAEO) exhibited the highest anti-Xoo activity, with an inhibition zone of 4.7 cm. It showed a MIC of 2.5 µg/mL and significantly reduced biofilm formation and xanthomonadin production by 42.1% and 22.6%, respectively, whilst enhancing scavenging activity by 76.67%, suggesting oxidative stress induction. Furthermore, its GC-MS analysis identified the presence of thymol (60.44%), γ-terpinene (17%), anisole (16.2%), sabinene (2.36%), carene (0.44%), myrcene (0.33%), limonene (0.27%), and terpinen-4-ol (0.26%) as major bioactive components. These compounds were validated through molecular docking with the RpfF gene (key pathogenicity factor), which revealed that thymol showed strong binding affinity (-5.5 kcal/mol) with RpfF chain A and had favourable pharmacokinetic properties, supporting its role as a lead candidate for anti-Xoo activity. The bio-control potential of TAEO was further evidenced by scanning electron microscopy (SEM) in which TAEO-treated Xoo cells proclaimed marked morphological disruption, including reduced cell density, irregular and sunken surfaces, and membrane damage. Thus, this is the first report demonstrating the potent anti-blight activity of TAEO, highlighting its potential as a sustainable plant-derived bio-control agent against Xoo.