Potential Plant-Based Antibacterial Agent: In vitro Antibacterial Activity of Rauvolfia tetraphylla Methanolic Leaf Extract

Abstract

Aims: The present study evaluated the in vitro antibacterial activity of the methanolic leaf extract of Rauvolfia tetraphylla against selected bacterial strains. Study Design: Laboratory-based in vitro experimental study. Methodology: Fresh R. tetraphylla leaves were collected, authenticated, shade-dried, powdered and extracted with methanol by cold maceration. The extract was tested against Staphylococcus aureus ATCC 25923, Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853 and Klebsiella pneumoniae ATCC 1706. Antibacterial activity was assessed by agar well diffusion at 12.5–200 mg/ml, and minimum inhibitory concentrations were determined by broth microdilution. Gentamicin served as the positive control, while solvent and media controls were included. Assays were performed in triplicate, and results were expressed as mean values with standard deviations. Results: The extract showed the highest activity against S. aureus, with a 26.56 ± 1.39 mm inhibition zone at 200 mg/ml. At the same concentration, inhibition zones were 13.55 ± 0.40 mm for E. coli and 11.89 ± 0.44 mm for P. aeruginosa. At 100 mg/ml, inhibition was observed only against S. aureus and P. aeruginosa. No inhibition zone was observed against K. pneumoniae. MIC values were 12.5 mg/ml for S. aureus, 25.0 mg/ml for E. coli and K. pneumoniae, and 50.0 mg/ml for P. aeruginosa. Conclusion: The methanolic leaf extract of R. tetraphylla exhibited in vitro antibacterial activity, particularly against S. aureus. Further studies are required to confirm the active constituents, reproducibility and safety before any therapeutic application can be considered.