Phytochemical-Antibiotic Synergy: Exploring the Antibacterial Potential of Calotropis procera in Combination Therapy

The rising problem of bacterial resistance necessitates alternative strategies to enhance antibiotic efficacy. This study examines the combined antimicrobial efficacy of the extracts of Calotropis procera and ciprofloxacin against specific bacterial pathogens. Crude extracts were prepared from the leaves and stems of C. procera collected in Makurdi, Nigeria. Using GC-MS analysis, we identified notable phytochemicals in the extracts from the plant's leaves and stems. The minimum inhibitory concentrations (MICs) for Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis, and Staphylococcus aureus were measured using a microdilution method. The checkerboard assay was utilized to evaluate the synergistic effect of C. procera extracts when combined with ciprofloxacin. The Fractional Inhibitory Concentration Index (FICI) was calculated using the formula: FICI = (MIC of extract in combination / MIC of extract alone) + (MIC of ciprofloxacin in combination / MIC of ciprofloxacin alone). The leaf extract showed an MIC of 3.10 µg/ml for B. subtilis and 8.33 µg/ml for E. coli, whereas the stem extract had an MIC of 4.20 µg/ml for B. subtilis. When combined with ciprofloxacin, the FICI values indicated synergistic interactions against E. coli (FICI = 0.4 for leaf and 0.3 for stem extract) and against S. aureus (FICI = 0.3 for the stem extract). In contrast, the interactions against P. aeruginosa and B. subtilis ranged from additive to antagonistic. The findings indicate that extracts from C. procera significantly enhance the antibacterial efficacy of ciprofloxacin, which may enable reduced doses of the antibiotic and offer a new approach to address antibiotic resistance. Nonetheless, additional in vivo research is necessary to confirm these promising results and to clarify the mechanisms involved in their action.