Antimicrobial and antioxidant properties of twelve Congolese medicinal plants

In Democratic Republic of Congo, many medicinal plants are used against infectious diseases. However, the biological activities of many of them have never been reported. In this work, methanolic extracts of twelve medicinal plants from the Lubumbashi area were investigated for in vitro antimicrobial activity by the microdilution technique [1, 2] and for free radical scavenging by the DPPH assay [3]. Antimicrobial activity against Staphylococcus aureus with MIC between 250 and 1000µg/ml was found in seven of the 12 plants (Coreopsis quarreischer, Ficus capensis, Acalypha senensis, Dalbergia nitidula, Combretum celastroides, Phyllanthus muellerianus, Smilax anceps). Escherichia coli and Pseudomonas aeruginosa were inhibited by two plants, Combretum celastroides and Smilax anceps; Combretum celastroides and Phyllanthus muellerianus, respectively. None of the extracts showed inhibitory effect on Candida albicans and five of the 12 plants were inactive against all the tested microorganisms. In the DPPH assay, all the extracts showed antioxidant activity with IC₅₀ between 4 and 180µg/ml (quercetin equivalent between 0.02 and 0.78).

Acknowledgement: Authors are grateful to Coopération Universitaire au Développement/Belgium (CUD) for financial support, Mr Kisimba for collection of plant material.

References: 1. NCCLS (2003), Approved Standard, 6th edition. 2 NCCLS (2002), Approved Standard, 2th edition. 3 Pandey, et al. (2005) Acta Pharmaceutica 55: 297–304.