Direct and indirect antimicrobial activity of Cordia gilletii extracts

The alarming incidence of antibiotic resistance causes an increasing need for new products that can act either by a direct antimicrobial activity or by inhibiting resistance mechanisms of germs of medical importance. Plants represent a potential source for this kind of compounds [1, 2]. Root barks of Cordia gilletii De Wild ( Boraginaceae ), a Congolese plant traditionally used for antimicrobial properties, were extracted successively by n-hexane, dichloromethane, ethyl acetate, methanol and water. These extracts were tested for direct antimicrobial activity against eight microbial species ( Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae, Enterobacter cloacae, Proteus mirabilis, Serratia marcescens and Candida albicans ) and for effect on antibiotic resistance by broth microdilution methods [3, 4]. The methanol extract showed direct antimicrobial activity against all the strains with MIC values ranging between 125µg/mL and 1000µg/mL, whereas the ethyl acetate and dichloromethane extracts showed activity on two ( Staphylococcus aureus and Escherichia coli) and three ( Klebsiella pneumoniae, Enterobacter cloacae and Serratia marcescens ) microbial species respectively. 200µg/mL of the n-hexane and dichloromethane extracts decreased the MIC of penicillin, amoxicillin, ampicillin and streptomycin 4–64 fold for S. aureus methicillino-resistant. Acknowledgement: Dr Lerson (CHU Charleroi, Belgium), Belgian Technical Cooperation. References : 1. Chariandy, C.M. et al. (2000), J. Ethnopharmacol. 64: 265–270. 2. Hatano, T. et al. (2005), Phytochemistry 66: 2047. 3. NCCLS (2003), Approved Standard, 6th edition. 4. NCCLS (2002), Approved Standard, 2th edition.