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Comparative of antibacterial activities of herbal extracts from Piper betel, Bauhinia scandens L. and Chromolaena odorata against gram-positive and gram-negative pathogens

biotechnology
microbiology
drugs-and-devices
pharmacology
public-health

Abstract

Background

Antimicrobial resistance remains a major global challenge and has increased interest in plant-derived compounds as alternative or complementary therapeutic agents. This study evaluated the in vitro antibacterial activity of ethanol-extracted Piper betel leaf (EPB), Bauhinia scandens L. stem (EBS), and Chromolaena odorata leaf (ECO) against common mastitis-associated pathogens.

Methods

The three herbal samples were prepared through ethanol extraction followed by freeze-drying. Antibacterial activity was assessed using disc diffusion assays at two extract concentrations. Minimum inhibitory concentrations (MIC) and minimum bactericidal concentrations (MBC) were determined through broth microdilution. Statistical analyses were performed to compare the inhibitory and bactericidal performance of the extracts.

Results

The extracts showed distinct antibacterial profiles. EPB and EBS produced the strongest inhibition zones against Staphylococcus aureus, while ECO displayed weaker activity. In agreement with diffusion results, EPB and EBS had the lowest MIC and MBC values for S. aureus, and both showed bactericidal MBC/MIC ratios. Activity against Escherichia coli was limited; measurable inhibition was observed only for EPB, and all extracts required substantially higher MIC and MBC concentrations compared with S. aureus. None of the extracts demonstrated meaningful activity against Pseudomonas aeruginosa. Across assays, inhibition zone size showed a negative correlation with MIC values, indicating consistency between diffusion and broth-based methods.

Conclusions

EPB and EBS demonstrated promising antibacterial activity against S. aureus, suggesting potential use as plant-based candidates for controlling Gram-positive mastitis pathogens. Their limited effects on Gram-negative bacteria indicate they may be best suited for targeted rather than broad-spectrum applications. Further phytochemical characterization and in vivo studies are warranted to evaluate their therapeutic potential in livestock health management.

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