Targeting multi-drug-resistant ESKAPE pathogens: antibacterial, antioxidant, cytotoxicity, and metabolic profiling of selected Cameroonian plants

Background

Different parts of Allanblackia floribunda, Calotropis procera, Hymenocardia acida, Irvingia gabonensis, Newbouldia laevis, and Xylopia acutiflora have been used traditionally across different parts of Cameroon to overcome infectious diseases, especially pneumonia. Hence, this study investigated the antibacterial potential of six Cameroonian medicinal plants against selected ESKAPE pathogens (Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Escherichia coli, Pseudomonas aeruginosa) as well as Streptococcus pneumoniae.

Methodology

The inhibitory activities of different extracts from six Cameroonian plants against the pathogens were evaluated by determining their MICs. Subsequently, the top four bioactive plant extracts were assessed for antibiofilm activity, time-kill kinetics, cytotoxicity (Raw and Vero cell lines), as well as antioxidant activities. Finally, the effect of the most potent extract, viz. ethanolic extract of Xylopia acutiflora steam bark, on bacterial morphology was elucidated through scanning electron microscopy while its phytochemical composition was profiled using liquid chromatography–mass spectrometry (LC–MS).

Results

Twenty-two out of the 32 prepared extracts showed significant antibacterial activity, with MICs varying from 31.5 to 1000 µg/mL. The ethanolic, methanolic, and hydroethanolic extracts from Xylopia acutifolia and ethanolic extract from Colotropix procera exhibited broad-spectrum activity, inhibiting and eradicating bacterial biofilm. Furthermore, the extract from X. acutifolia was shown to be the most effective scavenger against DPPH (IC₅₀; 83.79 ± 1.92 µg/mL) and FRAP (IC₅₀; 22.89 ± 1.36 µg/mL) radicals, while C. procera extract was the most effective against ABTS (IC₅₀; 67.95 ± 1.83 µg/mL). The extracts were demonstrated to possess low cytotoxicity on both Raw and Vero cell lines. In addition, SEM revealed that X. acutifolia elicited cell membrane rupture and consequently cytoplasm leakage in E. coli and P. aeruginosa. Twenty-four different compounds were detected in the X. acutifolia extract via LC–MS analysis, and it was hypothesized that the recorded bioactivity in the extract might be ascribed to these compounds.

Conclusion

Results from this study have scientifically validated the ethnomedicinal uses of the six Cameroonian plants as therapeutics for infections with X. acutiflora ethanolic extract displaying the highest bioactivity. Thus, there is the need for further investigations into phytochemicals from these plants as they could serve as important sources of novel antioxidants and antimicrobial agents.

Graphical abstract