Ursolic, oleanolic and betulinic acids: Antibacterial spectra and selectivity indexes

Ethnopharmacological relevance: Ursolic acid (UA), oleanolic acid (OA) and betulinic acid (BA), three hydroxyl pentacyclic triterpenoic acids (HPTAs) naturally found in a large variety of vegetarian foods. medicinal herbs and plants have been investigated for antibacterial activity. Aim of the study: To determine the antibacterial activity of UA, CIA and BA, as well as the toxic impact on eukaryotic cells. Materials and methods: Minimum inhibitory concentrations were determined against five reference strains (Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 25923 & ATCC 29213, Enterococcus faecalis ATCC 29212 and Pseudomonas aeruginosa ATCC 27853), as well as five anti biotic-resistant clinical isolates. Toxicity was evaluated against MRC-5 and HaCaT cell lines. Results: No antibacterial activity was observed for BA: while OA and more particularly UA, did show a moderate to good antibacterial activity, but limited to Gram-positive bacteria. Nevertheless, CA and UA were devoid of antibacterial activities against clinical isolates. Moreover, viability and cytotoxic assays demonstrated that the three compounds induced a significant cytotoxicity. Conclusions: Despite of a relative similar chemical structure; UA, OA and BA harboured different antibacterial activities, with more significant ones for UA. However, considering both viability and toxicity values, these compounds seem to have a significant impact on eukaryotic cell viability. (C) 2008 Elsevier Ireland Ltd. All rights reserved.