Antibacterial mechanism and green pesticide implications of multi-source compound botanical bacteriostatic agents

Screening green and high-efficiency bacteriostatic agents is crucial for the sustainable development of fruit and vegetable industry. Long-term application of chemical fungicides has caused increasingly serious problems including pathogen resistance, pesticide residues and environmental pollution. Meanwhile, single botanical preparations are restricted by narrow antibacterial spectrum, unstable active ingredients and single action targets. In view of the above problems, this study prepared compound botanical bacteriostatic agent FLR-1 by compounding extracts of Forsythia suspensa , linseed and rosemary. Its chemical constituents, antibacterial activity and action mechanism were systematically analyzed via LC–MS metabolomics, Oxford cup method and gradient dilution method. The results revealed that agent FLR-1 contained ten categories of metabolites such as sugars and glycosides, steroids, lipids and organic acids. It exhibited prominent inhibitory and bactericidal effects against 10 fungal strains and 2 bacterial strains at concentrations of 2.5–5 μL/mL, presenting broad-spectrum antibacterial activity across different microbial groups. Mechanistic studies confirmed that agent FLR-1 exerted its efficacy independent of extreme acid–base stress. Instead, it destroyed the integrity of pathogen cell membranes, increased membrane permeability and triggered the leakage of intracellular nucleic acids to inhibit and eliminate pathogens. This study clarified the direct antibacterial mechanism of multisource plant metabolites via combined action and multi-target membrane damage. It provides a novel strategy to overcome the limitations of single botanical agents, and offers theoretical references for the development of novel high-efficiency and low-toxicity compound botanical bacteriostatic agents as well as the prevention and control of pre-harvest and post-harvest diseases of fruits and vegetables.