Antibacterial activity of Azanza garckeana extracts (Malvaceae) in vitro and their potential use in respiratory infections.

Microb Pathog

Department of Therapeutics, Natural Products Unit, African Institute of Biomedical Science and Technology (AiBST), Wilkins Hospital Block C, Corner J, Tongogara and R. Tangwena road, Harare, Zimbabwe. Electronic address:

Published: January 2025

AI Article Synopsis

  • The ESKAPE pathogens (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species) are particularly dangerous for people with weakened immune systems, leading to high mortality rates from severe bacterial infections.
  • This study investigated the antibacterial properties of Azanza garckeana leaf and bark extracts against these pathogens using methods like broth microdilution for testing efficacy and GC-MS for analyzing bioactive compounds.
  • Findings revealed that hexane bark extract was highly effective against S. aureus and A. baumannii, while acetone bark extract disrupted bacterial membranes and showed antibiofilm activity against K. pneumonia

Article Abstract

The ESKAPE pathogens, namely Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species, pose a significant threat to individuals with compromised immune system, including children, people with underlying illnesses and patients primarily infected with viruses. Significant mortality rates have been documented as a consequence of severe pneumonia resulting from bacterial respiratory tract infections. Azanza garckeana has been reported to possess antibacterial and anti-inflammatory activities. This study aimed to determine the antibacterial activity of A. garckeana leaf and bark extracts against P. aeruginosa, K. pneumoniae, A. baumannii, and S. aureus. The broth microdilution method was used to evaluate antibacterial activity. The most active extracts were subjected to phytochemical analysis to identify types of bioactive compounds present using gas chromatograph mass spectrometry (GC‒MS). The effect of the extracts on the integrity of the bacterial membrane was performed using nucleic acid and protein leakage assay. Acetone bark extract was assessed for its potential antibiofilm activity using K. pneumoniae. The toxicity profiling of the most potent extracts was performed using sheep erythrocytes and mouse peritoneal cells. The hexane bark extract exhibited greater potency by inhibiting the growth of S. aureus and A. baumannii at a concentration of 200 μg/mL. GC-MS identified the presence of important bioactive compounds including, β-carotene, 9-hexadecen-1-ol, (Z)-, hexadecanoic acid, methyl ester, and 2,4-di-tert-butylphenol. Acetone bark extract exhibited antibacterial activity through disruption of bacterial membrane integrity, observed through significant nucleic acid and protein leakage. The acetone bark extract displayed promising antibiofilm activity against K. pneumoniae. Importantly, the extracts showed minimal toxicity, demonstrating less than 30 % haemolytic activity in sheep erythrocytes and were not toxic to the mouse peritoneal cells, instead boosting their growth. These findings suggest that A. garckeana may serve as a potential source of antibacterial lead agents for the management of respiratory infections.

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Source
http://dx.doi.org/10.1016/j.micpath.2024.107170DOI Listing

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