Antibacterial, antibiofilm and toxicity profiles of Argemone ochroleuca Sweet and Argemone mexicana Linn against phytopathogenic bacteria

Plant diseases remain a major constraint to agricultural productivity, and the growing resistance to synthetic pesticides necessitates the development of alternative control strategies. Argemone ochroleuca and A. mexicana are known to contain bioactive compounds with notable biological activities, highlighting their potential as eco-friendly alternatives. However, their activity against phytopathogenic bacteria remains underexplored. This study aimed to investigate the antibacterial, anti-biofilm, phytotoxic and cytotoxic activities of extracts from both plant species against phytopathogenic bacteria. Extracts were obtained using water, acetone, methanol and dichloromethane. Antibacterial activity was determined using the microdilution method, while the antibiofilm activity was assessed at initial cell attachment (T0), preformed (T8), and mature biofilm (T24) stages. Phytotoxicity was evaluated using a seed germination assay, and cytotoxicity was assessed using the tetrazolium-based colorimetric assay HEK cells. Acetone extracts of A. ochroleuca roots and A. mexicana shoot and root had the best antibacterial activity, with an MIC value of 0.06 mg/mL against Xanthomonas gardneri 1790. The highest biofilm inhibition was recorded at T0 on A. mexicana root aqueous extracts against Ralstonia solanacearum 1315 at 87.21%, indicating preferential interference with early biofilm development. Aqueous extracts showed no phytotoxic effect on tomato seed germination, whereas the acetone, methanol, and dichloromethane extracts caused significant inhibition. Most extracts exhibited low cytotoxicity on HEK cells, with IC 50 values greater than 0.020 mg/mL. These findings demonstrate that A. ochroleuca and A. mexicana possess potent antibacterial and antibiofilm activities, particularly against early-stage biofilms, with minimal cytotoxicity, supporting their potential as eco-friendly agents for plant disease management. • Argemone ochroleuca and A. mexicana demonstrated strong antibacterial activity • Significant inhibition of initial cell attachment was exhibited by the extracts • Water extracts had no phytotoxic effects on tomato seeds • Most of the extracts had no apparent cytotoxic effects • These plant extracts could serve as effective biocontrol agents