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, OA 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 antibiotic-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, OA 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.