Characterization of the antibacterial activity from ethanolic extracts of the botanical, Larrea tridentata

BACKGROUND: β-lactam antibiotics are a class of broad-spectrum antibiotics consisting of all antibiotic agents that contain a β-lactam ring in their molecular structures. β-lactam antibiotics are only known to be isolated from fungi (e.g. Acremonium chrysogenum, Penicillium chrysogenum and Aspergillus nidulans) and bacteria (e.g. Streptomyces clavuligerus). We have shown that botanical extracts prepared from Larrea tridentata have strong antimicrobial activity against several bacteria, including members of Staphylococcus and Streptococcus genera. METHODS: Through resistance studies, inhibitor assays, and ELISA testing, we demonstrated L. tridentata extracts may contain a β-lactam type antibiotic activity. RESULTS: Based on the estimated β-lactam concentration within the extract, the antimicrobial activity of the L. tridentata extract was approximately 2000–8000-fold greater against Staphylococcus as compared to other β-lactams, penicillin or ampicillin. In the L. tridentata extract, this increased activity was found to be associated with the likely presence of a cofactor leading to increased potentiation of the β-lactam activity. This potentiation activity was also observed to enhance the activity of exogenously added natural penicillin antibiotics. CONCLUSIONS: Although constituents were not isolated in this study, the results obtained strongly support the presence of β-lactam type antibiotic activity and antibiotic potentiation activity present in ethanolic extracts prepared from L. tridentata.