Exploring the Selective Antibacterial Effects of Natural Products Against Pathogenic and Beneficial Bacteria

Objectives: To determine the selective antibacterial effects of medicinal plants alone and in combination with prescribed antibiotics. Methods: Using in vitro well diffusion assays and turbidity measurements, we assessed the antibacterial activity of herbal extracts against gram-positive and gram-negative bacteria, including beneficial bacteria like Lactobacilli . Measuring the inhibition zone diameters provided initial screening for the natural products with antibacterial properties. Results: Among 31 tested herbal extracts, only six demonstrated notable antibacterial activity when used alone or in combination with prescribed antibiotics. These were effective against both gram-positive and gram-negative bacteria, except for radish seed, which was active only against E. coli . Most drug-herb combinations did not enhance the efficacy of antibiotics. Among the tested substances, only capparis spinosa root, vinegar, and bicarbonate inhibited the growth of Lactobacilli , whereas other effective herbal extracts had no harmful effects on beneficial bacteria. Conclusion: This study highlights specific herbal compounds with selective antibacterial effects that may offer therapeutic value, particularly in addressing antibiotic resistance. Notably, five active compounds did not inhibit the growth of Lactobacilli , suggesting their potential to target pathogens without disrupting the beneficial microbiota. Our findings support the use of natural products as antibacterial agents, although the absence of minimum inhibitory concentration (MIC) testing and phytochemical profiling of specific bioactive compounds limits the study. Further studies are needed to explore the clinical relevance and underlying mechanisms of these natural products.