Antibacterial Activity of Ritchiea albersii Gilg and Cynoglossum amplifolium Leaves Extracts against Selected Bacteria

Background: The increase in antimicrobial resistance worldwide has necessitated the search for alternative therapeutic agents. The leaf extracts of Ritchiea albersii and Cynoglossum amplifolium have been used as traditional medicine for the management of eye, ear and wound infections in Ethiopia.

Objective: The objective of the study was to evaluate the antibacterial activity of R. albersii and C. amplifolium against three common bacteria.

Materials and methods: In this experimental study, the antimicrobial properties of 80% methanol, chloroform and acetone extracts of R. albersii and C. amplifolium were evaluated against two Gram-positive bacteria (Staphylococcus aureus ATCC 25923 and Streptococcus pneumoniae ATCC 49619) and one Gram-negative bacterium (Escherichia coli ATCC 25922) using the agar-well diffusion method. Ciprofloxacin 0.05 mg/disc was used as a positive control. Furthermore, a preliminary phytochemical study was carried out.

Results: The zones of inhibition shown by all extracts of the two plants against the tested bacteria were significantly lesser (P < 0.05) than the standard drug. E. coli and S. aureus were the most susceptible strains for most extracts studied. The acetone extract of R. albersii exhibited a higher inhibitory effect (P < 0.05) against S. pneumoniae (16 mm) and E. coli (19 mm) compared with its methanol extract. The chloroform extract of R. albersii was more effective than its methanol extract (P < 0.05) against all tested bacteria. The acetone extract of C. amplifolium displayed a higher inhibitory effect (20 mm) against E. coli than its methanol and chloroform extracts.

Conclusions: The leaf extracts of R. albersii and C. amplifolium exhibited broad-spectrum antimicrobial activity, highlighting their potential as phytotherapeutic drugs in preventing and treating infections caused by S. aureus, S. pneumoniae and E. coli. Further investigations for isolating specific compounds and elucidating mechanisms are required to address the need for novel antibacterial drugs.

Keywords: Antibacterial activity; Cynoglossum amplifolium; Escherichia coli; Ritchiea albersii; Staphylococcus aureus; Streptococcus pneumoniae.