Screening for Antibacterial and Antiprotozoal Activities of Crude Extracts Derived from Mexican Medicinal Plants

Background: Crataegus mexicana, Hyptis albida, Larrea tridentata, Ocimum baislicum, Prunus serotina, and Smilax spp. are used in Mexican traditional medicine to treat respiratory and gastrointestinal diseases such as flu, cough, diarrhea, dysentery, and other parasitic or microbial infections. Therefore this study was aimed at the pharmacological prospection of these plants against eleven bacterial species and three amitochondrial protist pathogens. Material and methods: The fruits or aerial parts of C. mexicana, H. albida, L. tridentata, O. baislicum, P. serotina, and Smilax spp. were extracted with different solvents. The antibacterial properties of organic and aqueous extracts of these plants were determined by the microdilution method and the microplate alamar blue assay against Stenotrophomonas maltophilia, Escherichia coli, Acinetobacter baumannii, Pseudomonas aeruginosa, Klebsiella pneumoniae, Enterobacter cloacae, Staphylococcus aureus, methicillin-resistant S. aureus, Listeria monocytogenes, Enterococcus faecalis, and Mycobacterium tuberculosis, whereas anti-protozoal activities of extracts were evaluated by a vial micro-assay against strains of Entamoeba histolytica, Trichomonas vaginalis, and Giardia lamblia. Results: H. albida, Smilax spp, and C. mexicana showed good activity against the Gram-positive strains, S. aureus, methicillin-resistant S. aureus, and E. faecalis. Four extracts (C. mexicana, H. albida, O. basilicum, and L. tridentata) showed good activity against E. histolytica, T. vaginalis, and G. lamblia. Conclusion: The extracts of these six medicinal plants could be a source for new antibacterial and antiprotozoal drugs. For this reason they are currently under investigation to isolate and characterize their active compounds.