Antibacterial and Antifungal Activities of Saponin Extracts from Three Congolese Medicinal Plants of the Fabaceae Family

Background and Objective: Antimicrobial resistance is a critical global health threat, particularly in Sub-Saharan Africa, where access to effective treatments is very limited. Saponins from Fabaceae plants exhibit broad pharmacological properties, yet several Congolese species remain pharmacologically unexplored. This study evaluated the antibacterial and antifungal activities of saponin-rich extracts from three Congolese Fabaceae: Millettia laurentii De Wild., Millettia dubia De Wild., and Pentaclethra eetveldeana De Wild. & T. Durand. Materials and Methods: Saponins were extracted from the trunk and root bark of plant species using 80% methanol maceration and reflux, followed by diethyl ether precipitation. A dialyzed fraction of M. dubia was prepared using a 10,000 Da cut-off membrane. Antimicrobial activity was assessed by broth microdilution assay against Staphylococcus aureus ATCC 25923, Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 15442, and Candida kruseiATCC 6258. Results: Extraction yields ranged from 3.27 to 3.6%. All five extracts selectively inhibited P. aeruginosa; the dialyzed M. dubia extract showed the greatest potency (MIC = 15.625 μg/mL). No activity was detected against E. coli or S. aureus. The dialyzed M. dubia extract also demonstrated excellent antifungal activity against C. krusei(MIC = 15.625 μg/mL), outperforming fluconazole. Conclusion: Millettia dubia saponins exhibit potent activity against P. aeruginosa and C. kruseifollowing partial purification, suggesting the antimicrobial potential of this species. Our findings contribute to the valorization of Congolese flora as a potential source of new antimicrobial leads.