In vitro antibacterial activities of the leaf extracts of Aloe macrocarpa Tod (Aloaceae)

Introduction: Infectious diseases have been threats to public health across the globe. The use of the leaves of Aloe macrocarpa Tod used for the treatment of infected wounds has been a common practice in North Gondar, Ethiopia. The objective of the study was to investigate the in vitro antibacterial activities of the leaf extracts of Aloe macrocarpa. Methods: Maintaining sterile conditions, the latex and gel of Aloe macrocarpa were collected and dried at room temperature. The crude gel was further extracted using 80% methanol. Then, antibacterial test was conducted against Staphylococcus aureus, Streptococcus pneumonia, and Streptococcus pyogenes and four Gram negative bacterial strains: Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumonia, and Salmonella typhi by agar well diffusion and broth dilution methods. Results: The three extracts showed different degrees of inhibitory activities against tested bacteria at 2, 1 and 0.5 mg/ml concentrations in a dose dependent manner with statistically significant values (P = 0.05). For all tested bacteria, the zone of inhibition ranged from 0.00 to 23.00 +/- 0.577 mm. The minimum inhibitory concentration (MIC) values ranged from 31.25 to 4000, 31.25 to 2000 and 62.5 to 8000 mu g/ml for the latex, hydroachoholic gel extract and crude gel, respectively. The lowest minimum bactericidal concentration (MBC) was 31.25 mu g/ml for the latex against Salmonella typhi. Conclusion: From this study it can be concluded that the latex and gel extracts of the leaf of Aloe macrocarpa showed an inhibitory activity against tested bacteria. Therefore, the results demonstrated the traditional claims of this plant for the treatment of infected wounds.