Antibacterial activities of Thankuni (Centella asiatica) leaf extract against Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa

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Antimicrobial resistance is a major global health threat, driving the search for cost-effective alternatives. Plant-based drugs from traditional medicine are promising candidates due to their potential for reducing the development of resistance. An experimental study was conducted in the Department of Pharmacology & Therapeutics in collaboration with the Department of Microbiology of Mymensingh Medical College, Bangladesh, from July 2022 to June 2023, to evaluate the in vitro antibacterial activities of aqueous and ethanolic extracts of thankuni (Centella asiatica) leaves against Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa. Antibacterial activity against Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa was evaluated using the Kirby-Bauer disc diffusion method. The minimum inhibitory concentration (MIC) was determined by the broth dilution technique, with ceftriaxone as a control. All procedures were conducted in accordance with standard clinical laboratory protocols. For the aqueous extract (ATLE), the largest zone of inhibition (ZOI) at the highest tested concentration (100 mg/ml) was recorded against S. aureus (25 mm), followed by E. coli and P. aeruginosa (both 19 mm). A definite inhibitory effect (ZOI >8 mm) for ATLE began at 40 mg/ml for S. aureus, 60 mg/ml for E. coli, and 100 mg/ml for P. aeruginosa. The ethanolic extract (ETLE) exhibited superior antibacterial efficacy compared to ATLE (p<0.001). At 100 mg/ml, ETLE produced zones of inhibition of 26 mm against S. aureus, 25 mm against E. coli, and 24 mm against P. aeruginosa. Notably, the ethanolic extract began showing definite activity at much lower concentrations: 20 mg/ml for S. aureus and 40 mg/ml for both E. coli and P. aeruginosa. The two extracts at equivalent concentrations showed that the enhanced activity of the ethanolic extract was particularly significant against the Gram-negative organisms, E. coli and P. aeruginosa (p<0.01). The MIC values showed that ETLE was more potent than ATLE. The MIC of the aqueous extract was 30 mg/ml for S. aureus, 60 mg/ml for E. coli, and 75 mg/ml for P. aeruginosa. In contrast, the MIC of the ethanolic extract was significantly lower, at 20 mg/ml for S. aureus and 40 mg/ml for both E. coli and P. aeruginosa. This represents a 33.3% increase in potency against S. aureus and a 33.3% and 46.7% increase against E. coli and P. aeruginosa respectively, when using the ethanolic solvent for extraction. As expected, the standard antibiotic control, Ceftriaxone, demonstrated far greater potency, with MIC values in the microgram range: 1.5 µg/ml for S. aureus, 1.0 µg/ml for E. coli, and 1.5 µg/ml for P. aeruginosa. Both aqueous and ethanolic extracts of thankuni (Centella asiatica) leaves possess definite antibacterial activity against the tested organisms, with the ethanolic extract being more potent. CBMJ 2026 July: Vol. 15 No. 02 P:27-34

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